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cubic trefoil knot
I would like to create an animation of a cubic trefoil knot.  It is a very interesting 3D structure.  Use Google images to see what one looks like.  I would like to do an animation where I start with 1 block and either extrude or stack blocks to create one, one block at a time.  It would look something like one block then another block next to it in the Y axis, repeat to three, then start adding blocks in the Z direction until you have a stack, then start adding blocks in the X direction, etc.

Hello and welcome. What is your question, what part of the workflow are you stuck with?

Actually, that is the problem.  I really don't know what a workflow is.  What I want is similar to stacking blocks.  I want to stack blocks to create a cubic trefoil knot.  I have created one by extruding surfaces, but I want to animate the process as I do it.

I can't see how it could work with Arrays or Dupliframes. If I had to do it I would do it with cubes appearing in the scene the one after the other (keyframes on the eye icons of the cubes, in the Outliner). It's not the most intelligent way but it works. I guess you can do this kind of thing with Animation nodes? Also, maybe, a series of Boolean that would reveal the shape?

Suggest adding an image and or link to your question, rather than suggesting to readers to google it.  What does the one you created look like?

I came up with an answer but it does not work. I will leave here in case anyone can fix the final hurdle. Create a Curve as the knot, use the Curve as a Curve Modifier on a Cube that has an Array Modifier. This produces non 90 degree angle results so add a Remesh Modifier set to Blocks. Looks great, reduce the number of items in the Array and the moment the knot is smaller that the original bounding box the mesh jumps in location and size, very visible with low array count. This is because the Remesh Modifier uses the Bounding Box to determine Block size and Bounding Box can not be forced.

You can do this with DupliFrames.
Starting with a cube, and a path for the knot. (I made my path by duplicating selected edges from a 4x4x4 array of cubes and then  AltC converting the mesh to a curve)

In the cube Object Properties > Duplication panel, set duplication to 'Frames', the Start to 1, and the End to 36. Uncheck 'Speed'.
In the path's Data > 'Path Animation' panel, check 'Path Animation' and set the Frames to 36, uncheck 'Follow'.
In object mode, with the cube and path selected, (path last), CtrlP parent the cube to the path, with 'Follow Path' selected.

You may have to hit AltO to clear the origin of the cube and make it sit on the path. You may also have to alter the orientation / scale of the cube in Edit Mode to get the overall look you want.
Now you can animate the build block by block, Keyframing the cube's Duplication > 'End' field.

great method but why are the cubes invisible in Render?

@moonboots YIKES! thank you!? The duplis do render in Internal, but not in Cycles, until they'e made real, and then, of course, they don't animate. More digging, or it's abandon this method? I've found no commentary on this apart from bug reports in about 2014, which are marked fixed.

I followed your instructions and they do render in cycles. I did not apply an materials or make any changes.

here is the .blend. I do have different number of vertices but otherwise the same. https://blend-exchange.giantcowfilms.com/b/5249/

Thanks, @rob.. that's very helpful, because yours renders for me, too. Now, when I've got some time, I can focus on  trying  to figure out what the differences are ..  it would be odd for both moonboots' and my files to be corrupt.

OK, got it. Both @moonboots and I accidentally had duplication set to 'Frames' on the curve. Must be an easy slip, if we both made it..

There must be an intelligent way to do it, like Animation nodes, but anyway here is a way with the Boolean modifier:

Create your Knot.
Create one cube per section and scale them so that they encompass each section of the Knot.
Make them transparent and invisible in Properties > Object > Display and Cycles Settings (see screenshot).
Give your Knot as many Boolean modifier as you have cubes, and in each modifier chose one of the cube as Object.
Now in the Dopesheet window, go to frame 1, select all your cubes in the 3D view and press i > LocRotScale.
Move the green bar in the Dopesheet window, come back to your 3D view, move up the first cube and press i > LocRotScale. You've created a second keyframe for this cube and Blender will interpolate the movement from position 1 to 2. It will reveal the part of the Knot that was contained in this cube.
Maybe sometimes you'll have to scale down the cube instead of moving it.

I couldn't help overhearing you mention Dupliverts --  what would you animate, in that case? .. (I've popped the Blend into my answer ...)

Yes you're right, my bad, but I don't know why I have a bug with your method, I'm trying to understand why

there's a cube missing on the angle: https://zupimages.net/up/18/37/iky0.jpg

the file: https://blend-exchange.giantcowfilms.com/b/5245/

There's an on-for-so-many frames, off-for-so-many frames option in the cube's Duplication panel..-- you have it on for 9, off for 1.  1 & 0 will fill your curve.


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Cannot smooth without trouble on my mesh
I'm working on my mesh which looks like this :

As you can see the surface is not smoothed. Then I apply the smooth option and it gives me this result :

It is the third times I start again this mesh... I cannot understand how to apply the boolean modifier without getting in troubles.
Thank you for your help.

please show a screenshot of your mesh, it must be bad, or share your file

Use the bevel or the edge split modifier.

https://blender.stackexchange.com/questions/70575/how-do-i-fix-a-boolean-bisected-surface-edge

Thank you for your helps, it is solved.
What I have done is :
I have added a subdivision modifier

Then I have smoothed the surface. At this time, problems were still present on my mesh.

Finally, I have activated auto-smooth option

What I get is alright :

Thank you for your help guys !

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


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Why some hair particules doesn't apply material?
I'm trying to create grass field.
I have created a group of grass. I have assigned the same material (blue for the test) to every object of this group (called Herbe).

Then I have created a plane, subdivided and applied fractal. Then I apply particles on it to get grass springing. This is the particules option I have chosen :

Despite this, all is not blue. Some groups of grass doesn't take the blue color.
Would you know the reason ??

Thanks !

Can you provide the .blend file?

Thank you for your reply. Finally, it was because I had duplicated my plane, that's why I got this result....

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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Blender boolean modifier difference make distorsion
I'm trying to create a difference between two objects.
Let's see my object below :

As you can see, I get a really bad result. I would like to show you my shape before applying the boolean modifier.

Any idea how to avoid this distortion ?

I think it gives what it is supposed to give, to have sharp edges you need to add edge loops close to the one already existing, your boolean won't do it, but could you please share your file? https://blend-exchange.giantcowfilms.com/

Thanks, in this case @miceterminator solution is working.

The problem is that you apply the Subdivision-surface Modifier AFTER the boolean modifier. This means the hole you try to model using the boolean gets subdivided and "distorted".
The order of modifiers matters!

Thanks a lot, indeed it was because my boolean modifier was before the subdivision modifier.


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Help to improve my video
I have produced a short video but I'm not really enjoyed of it. Images are quite blurry and it is not nice to watch. When the camera move, we can kind of sparkles.
Would you have advise to improve it ? Would you have reasons for this poor quality ?
This is the video  : https://youtu.be/NQD0zOMuNmY
This the parameter of the animation :

I think most of your blurring is coming from the denoising post-process.
firstly, make sure motion blur is not turned on.
To avoid blurriness from the denoising, you have to increase your sampling.
256 or 512 should do it,. but will take a lot longer to render.
Alternatively, try using Blender 2.8 and use the EEVEE renderer. It is so much faster - and your scene doesnt require any complex light paths, so it should work really well.
Good luck!

Thank you for  your advise ! Motion blur is not turned on and my sampling is already at 600 ... Would you have another idea ?

Well, you could try a full HD render. set the image size to 1920 x 1080, and export to PNG. PNG s lossless, so it will produce very high quality source.
Then create your video from the PNGs. There are loads of free apps that will do this for you - but I can't advise which one. I use Adobe Media Encoder.
But I think you will get better results with EEVEE in Blender 2.8 - it is so much faster.

No worries! Let me know if it helped


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Help to convert root animation to in place animation
I have a root animation and need to convert it to in place, if I disable the the Y movement curve in Y, the body keeps in place but the feet still going forward and I don’t know how to make them keep the motion while preserving their position related to the root. Not sure if this is possible or if is too advanced, here’s a gif showing the problem:

Does anybody knows what settings should be changed in order to make the feet movement happens in place?

you should make the root follow the feet at the exact same speed, then deactivate the root

Thanks for the answer, the original root movement was following the feet already. What I did was just unmark the root curve to make it stay in place. But with the feet I don't know how to make that happen cause their movement are more complex. Not sure if I understand what you meant here.

so maybe your armature is not correctly build, because it means that your feet are completely independant from the root, which should not be the case, their controler should be parented to the root

I unparented the feet from the root to make steps animation easier, cause if the're linked the feet keeps moving with the root (obviously), which makes a run forward animation harder to work with once I must correct the feet position frame by frame. But now, even if I parent the foot with the root (keep offset), the result is like this: https://imgur.com/a/gnrSWuI

if your goal is to make a still walk cycle animation, I've given a method here, I hope it helps: https://blender.stackexchange.com/questions/159782/lego-walkcycle-sliding-problem/159796#159796

I'm afraid my scenario is more complex than it looks. My goal is to build a "partial root motion" to use in Unity. Firstly, I  build this animation with root motion in blender and extract the movement coordinates of the root in a txt using a script. Then I need to convert the exact same animation to in place in order to work with it in Unity. The coordinates extracted before will be used to create a movement curve in Unity. All of this work in an attempt to conciliate movement responsiveness, using code and movement precision, using that root motion coordinates in Unity.

But I'll take a look at that post, maybe there's something for me there...

well it gets a bit too complicated for me, maybe someone will be able to understand your needs   ;)


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How to make an animation aiming an specific character speed (for a game)?
So, I need to make a run animation for my game. Considering motion capture isn't an option for now, I believe I have only 2 ways to build this, in place animation or moving the character's root around. Almost all tutorials regarding animation (for games) are made with in place loops, this tells me this way is the best or at least the easiest way to do things. But I would like to animate the character running at an specific speed, let's say 30 km/h. Because of that requirement, I think the animation must be built moving the character's root. That being said, is there any way to actually measure the root speed in Blender before hand?
This was my rational behind the doubt, feel free to point any misconceptions that I might have said.

Well, 30 km/h is about 8 m/s, and a full-size human's stride is about 1 meter, so your character needs to take about 8 or 9 strides per second.

Thanks for the answer. Ok, a sprint stride should be more than that as the movement is more broad than a regular stride. I still have doubts about how to build the animation itselft, but I'll try to make more tests before asking more questions.

I searched for pose running method and found some nice sequences you could use as reference images. Note that in the Pose method speed is increased by increasing cadence not stride length.

Thanks you, but I wasn't talk about the poses. My doubts now are related the way I should animate, I believe I must build in place animations to import in Unity, but doing that, I can't tell the what the actual speed of the character. Like I said, there are more things to consider here, I'll try to make some tests, my next question would probably belong to the gamedev session...

Just figure out that the animation must be build moving the root in my case, if I use stationary clips, I would need to add the root motion inside Unity using it's animation curve system, which seems a little harder to work with. So I think I must animate moving the character around in the end..


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Is there any root motion workflow that doesn't require feet adjustments on frame by frame basis?
been searching for an hour or so, but wasn't able to find an specific answer about this problem. I need to make animations moving the character's root around for my game, so in place animations aren't a possibility. For now, I moved just the root bone (whole character) in straight line to ensure it has the speed movement I need in game, but now I need to start to add the actual feet movement to this animation movement. It happens that both feet follow the root movement (obviously), even when one of them should be planted. I did find some information pieces around the web, but nothing fixed this problem for me. I really need a best workflow for this, cause fixing the feet position on frame by frame basis seems to be a very bad, not to mention time consuming, way to do things.
I even considered unparent the feet from the root, but I'm positive this will cause problems in Unity as I need to use Humanoid rig there, which presupposes that the whole bone chain is connected to a single root.
I'm using Blender 2.8 and my rig was genereted by Makehuman, with the optimized for game engines option checked.
Does anynone knows a good workflow for this case? Maybe I missed something in my previous searches, cause this doesn't seems to be a big deal at all, it must have a better way to this..
Thanks in advance for any insights.

Have you seen the Royal Skies series on rigging Blender characters for Unity? The linked video looks like what you are asking about, the character's root seems to be moving with the character.

Thanks, but I already watched this videos, it wasn't what I meant. His animations are "in place" in the preview window in Unity, which means that the movement is being applied by code, probably. This is the kind of animation I want to do:
https://youtu.be/j7XZ3Q8JNfM?t=71

are you sure you need to move the root bone? If your goal is to make your character walk without any feet sliding, I gave a solution here: https://blender.stackexchange.com/questions/159782/lego-walkcycle-sliding-problem/159796#159796

Well, move the root around seems the right decision considering I need root motion on Unity. Also, I want to make sure that the character moves at certain speed. The method described yesterday worked for what I need so far. Do you think there's more to consider here? Does move root around may cause any issues that Im not aware of?

Use IK for the feet that are unparented to the root.  These IK targets exist only as controls (and you can, if you'd rather, even use an empty as the target instead of the bone.)

So a guy on Blender Artists gave a suggestion that worked in my first test. Create 2 auxiliary bones and link them on each foot using the copy transform modifier, this makes the feet follow these auxiliary bones instead of the root, overwriting the original parenting of the armature for the animations, while keeps the original parenting scheme in place for exporting.
If anyone need more details on this method, the complete answer can be checked at:
https://blenderartists.org/t/is-there-any-root-motion-workflow-that-doesnt-require-feet-adjustments-on-frame-by-frame-basis/1247260

You are misunderstanding the idea behind the Root bone.
Your body animation should be controlled by a body Master bone, which is usually around the center of mass - for example a Master Hip bone, which moves all deforming bones around.
You can leave the controller bones like IK and Pole target bones parented to the Root bone.
When you do your walk cycle animation you usually start keying the poses in place (like on a treadmill). Why? Because it is easier to observe your animation and not chasing the body around.
Once you are done with the "treadmill" walk cycle you can use the Master Hip bone to advance in space one cycle of your animation.
Once you are done with that and you would like to continue moving forward - you can make your animation cyclic and push (animate) the Root bone forward every time a cycle is complete.
Basically the Root bone serves to reposition the looping animation in 3D space seamlessly.
If you do more complex animations that do not require repetition you don't need to animate the Root bone at all.

Use either Inverse Kinematics and dont parent those bones to the root, or use a secondary armature (or bones not parented) from which you will copy the rotation and location. Mark every bone that doesnt deform directly the mesh as those as no Deform, so those dont get exported.


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How does one seamlessly loop an animation containing a Noise modifier?
I've searched and found some ineffective "solutions" to the issue I am experiencing.
I am animating a flickering candle flame and there is probably a much easier/more effective way to do this, however, I'm extremely new to Blender and CGI in general.
I have an object that I applied my candle flame shader to and opted to use a Noise modifier in the Graph Editor to manipulate the X, Y and Z scale of said object.
Mixing in an emission shader to the object did not give the effect I was going for. I opted to add a point light behind the object and again, use a Noise modifier in the Graph Editor to manipulate the Power and Z location. I also added a low Watt point light in front of the object, to illuminate the front surface, since the light behind washed out the flame shader due to transparency. (I believe)
I've been able to closely match the power of the light to the flame "flicker" size as well.
Where I'm falling short is the seamless loop of the animation. My first and last frames are not even close so there is a stutter at the end/beginning of the animation loop.
I have tried to manually set keyframes at the start and end of the animation. (Did not work)
I have tried to use the Restrict Frame Range setting with just the Noise modifier. (Did not work)
I tried to switch from Eevee to Cycles and use the Restrict Frame Range setting with that as well. (Did not work)
I really want to stick with Eevee as the Render Engine using Blender 2.8.
I suppose the gist of all this are the questions I have.
1) Is there a more effective/more simple way to achieve this effect using Eevee?
2) Is there a way to make the loop seamless while using the Noise modifier without having to endlessly tinker with the Noise settings to align the first and last frames?
The video is here:
https://youtu.be/qjzqhZsvGBw
There is no audio since I don't have a mic yet.

To loop a noise-based animation
One approach, I can't guarantee it's the snappiest, but it has some advantages.
You could use the NLA editor, to make an action loopable, in much the same way as you would make an image tileable  in an image editing application. For an image, you might split it down the middle, swap left and right halves, and blend across the discontinuities at the center. Same here.
Here's a noise-based animation, 100 frames, which doesn't loop.

In the Graph Editor, take the curves with noise modifiers, and convert them to actual keyframes, by using Header menu  > Key > Sample Keyframes

Switch to a Dopesheet > Action Editor window, and crack open an NLA window below it. An action should automatically have been created, which you can Push Down to the NLA editor, as a working strip.

In the NLA editor, you can ShiftA add a track. Put the cursor halfway down your strip, select it, and Right-Click menu, or Y, split the strip under the cursor.

Now you can select the halves of the strip separately, drag one of them to the spare track, and swap the halves, so the cuts are against the ends of the animation. You will have to shorten the overall length, so there's an overlap between the strips:

To get the automatic mixing in the overlap between the strips you will have to set the Auto Blend in the NLA's N panel:

This example produced a looping 86-frame animation:

.. Which can be baked into an action in its own right by using 3D View > Header > Object > Animation > Bake Action. You can reuse and adjust the loopable noise action with other objects, so long as the same properties are being animated, or even cut and paste the keyframes between channels of different types.

Have you tried adding the F-curve modifier? Make it cyclic, and I believe it should start the animation on the correct frames. I think the hotkey is ctrl + shift + M ?

Since the time of posting, some textures have been updated to 4 dimensional, which may change the parameters of the question.
However, I have a related answer here that I thought would be applicable.  In particular, if you offset the coordinate space origin and then rotate in such a way that the noise texture moves upwards through the flame it should provide you with texture distortions that rise just as the hot gas from a flame would rise through the surrounding atmosphere.

I would try to adjust the animation length so that it fills two conditions:

animation ends with curve going the same direction as when it ends - in your example, at start your curve 'falls down', so you should end your animation when curve falls down.
I would make sure it ends just before reaching same value as it had on start.

It might not be perfect, due to different momentum, but might get you close enough

Thanks for the info. I didn't realize the curves were not going in the same up or down direction at the start and end.
I am aware of the offset frames to make things smooth with either a -1 start or +1 end so the last frame is not identical to the first frame.
Again, this is taking so much tweaking, which I'm trying to avoid, but seems like I'll just have to spend the time.


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Normal Glass but behaving like mirror?

the light source is hdri and light portal in the windows.
i use camera transparency setting and glass transparency. but some of the windows glass behave like a mirror.

Well, that's how glass works... If you want transparency without reflection, you can use a Transparent BSDF shader.

Hello and welcome :). Real glass will actually act as a mirror under a shallow viewing angle. In your case, it doesn't look too realistic so there might be other issues. You can share your file, so others can take a look.

Try adding a glass with a transparency mix shader, and set the IOR to a low level.

I found a bit of a workaround to this issue. It's not ideal for every situation but if you lower your alpha it can solve this issue.

Hi, thanks for the post. This site is not a regular forum, answers should be substantial and thoroughly explain the solution and required workflow. One liners and short tips rarely make for a good answer. If you can [edit] your post and provide some more details about the procedure and why it works feel free to restore it, otherwise it may be deleted or converted into a comment. Perhaps add a few images illustrating the workflow and final results. See How do I write a good answer?


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Artifacts when smoke and glass interact
https://youtu.be/_YHDpam17fs
Can anyone think of an obvious reason the mug and the smoke simulation create these weird artifacts? The setup should in theory be pretty simple. I can post the blend file if anyone wants it. I've gone nuts researching and trying different things to fix it.

I'm going to guess that Blender doesn't like parts of the smoke intersecting with the glass. Try adding a new domain object that doesn't touch the glass, rerun the sim and see if that helps at all.

Yeah I thought that too, but the smoke domain isn't interesting with the glass at all: https://imgur.com/a/sKIVK6X


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Blender 2.81 32bit
Will there be a version of blender 2.81 for 32bit windows as there was for 2.80?
In my working environment we are currently unable to upgrade PCs.

Ask developers.

Blender 2.80 was the last release for Windows 32-bit. This was announced on the bf-committers mailing list.

Hi all,
Blender 2.80 was the last release where we officially support 32 bit
  Windows and Linux builds. For Blender 2.81 there will be only 64 bit
  builds.
We will continue to support it to the level that we do for example
  ARM. That is we keep the Blender code working independent of the
  processor architecture, particularly for Linux packages. But we don't
  actively test them or release our own builds.
Computers that meet the minimum graphics card requirements for 2.80
  practically always have a CPU with 64 bit support as well. That means
  the effective number of 32 bit users is very small by now.
The associated task on developer.blender.org is here:
  https://developer.blender.org/T67184
Thanks, Brecht.

It's not in the blender release archive so you would need to build it yourself, can't even find it on https://graphicall.org which would suggest that it's not a common thing to look for.
You'd probably find that it's only the Windows part that is 32-bit unless you are running some seriously old hardware ( more than 10 years old ), if that is the case then you're likely to have graphics card issues.  If it's a licensing issue, have you considered installing a 64-bit Linux instead, perhaps on a second disk?


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What is the difference between Spin and Spin Duplicates?
In Blender 2.81 there are spin tools. The first one is Spin tool and the other is Spin Duplicates. I used both of them and didn't see any difference. What is the difference? If you know the answer please share with me. Thanks :)

Spin tools creates a revolution surface from the selected geometry, while the Spin Duplicate operator creates a circular duplication kind of "polar array" of the selection.

Current issue I see is that apparently using the tools from the toolbar doesn't seem to automatically set the correct operator preferences, making them by default behave the same unless you manually untick the Duplicate option which seems like a bug.

Thanks for the answer. I think this one is a bug too. Both Spin and Spin Duplicates have use duplicate option. How can I call Spin Duplicate operator then? (Not from toolbar)

Spacebar menu, like all operators, otherwise create a dedicated hotkey


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Delete all meshes in an operator?
I am new to Blender Python. I would like to delete all meshes in a scene. How can I add for and if statement in a simple operator? Here is the simple operator template.
import bpy

def main(context):
    for ob in context.scene.objects:
        print(ob)

class SimpleOperator(bpy.types.Operator):
    """Tooltip"""
    bl_idname = "object.simple_operator"
    bl_label = "Simple Object Operator"

    @classmethod
    def poll(cls, context):
        return context.active_object is not None

    def execute(self, context):
        main(context)
        return {'FINISHED'}

def register():
    bpy.utils.register_class(SimpleOperator)

def unregister():
    bpy.utils.unregister_class(SimpleOperator)

if __name__ == "__main__":
    register()

    # test call
    bpy.ops.object.simple_operator()

Here is the "for and if statement" for deleting all mesh objects.
for obj in bpy.context.scene.objects:
    if obj.type == 'MESH':
        obj.select_set(True)
    else:
        obj.select_set(False)

bpy.ops.object.delete()

I don't know if this is the right method. I need help.

Replace the for loop in the main function by the lines at the end of your question

It doesn't work. Maybe I placed it wrong :(


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is there a way to make blender look for textures in the current directory?
I constantly move folders around and every time all texture files are pointing in the wrong directory and are missing

https://blender.stackexchange.com/questions/56683/moving-all-files-to-a-new-computer-my-concern-is-links/ https://blender.stackexchange.com/questions/47576/how-can-i-move-a-project-that-includes-images-as-planes/47586

You can store paths relative.
Save your file first. When importing an image, make sure the checkbox Relative Path is checked. (Lower left of the open image dialog.)

Examining the image in the image editor will reveal, that it's path starts with two slahes  //.

When relative paths are supported, the File Browser provides a Relative Path checkbox, when entering the path into a text field, use a double slash prefix (//) to make it so.

Relative paths are the default but this can be changed in the File tab of the User Preferences Editor.

So make sure, that relative paths are used by default by checking the box.

Now all paths relativ. Moving the .blend file and all image (etc) files, preserving their relativ location in the file structure, will not break the link in the .blend file.
However, if the relativ path changed (e.g. you renamed the images folder to textures), the links will be broken. You can restore them by searching for missing files. Go to File > External Data > Find Missing Files. Choose the directory containing the missing files and Blender will try to reconnect them.

Also next to this menu entry is the useful "Make all paths relative".


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Material preview mode transparency (Blender 2.8 Eevee)
I am in the material preview mode in Blender 2.8, using Eevee renderer. What material settings do I need to set, to get a transparent object in the viewport? The use-case is when modelling an object with reference side/front/top images - I'd like to be able to see the image behind the object that I'm modelling. Otherwise, the image is covered by the mesh that I'm working on.

Then I cannot see the images on the reference planes (as they are applied as materials). Or is there a setting to do it?

Solution 01
Add a reference image
Blender can add Reference images, that are visible in the 3D viewport, but not in renders.
They're great choice for modelling, and have many options available.
Add > Image > Reference

Solution 02
Enable transparency in Eevee
To make a material appear transparent in Material preview, use the Alpha value.
Don't forget to set Blend mode to Alpha-blend.
(If you cannot find these settings, switch to Eevee render engine in the render tab)


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Smoke jet simulation?
I would like to animate a jet of smoke as in this video clip (from the movie Interstellar). Here's a short preview:

Note the important elements are:

The smoke is translucent
The smoke is very fast at the exhaust
The smoke is turbulent and its "radius" increases away from the source, becoming more turbulent
The smoke has quite a well defined "contour" - it is not washed out, but ends abruptly in sort of sharp turbulent blades towards the end

I would also like to be able to toggle the jet on and off via a parameter that can be keyframed, simulating the jet firing/shutting off.
So far, I can get a washed out (4 not satisfied) and fairly uniform (3 not satisfied) jet of smoke using pretty much the default Quick Smoke properties together with a particle system flow source. However, I am unable to get the rich turbulent texture of the smoke in the above video. I also do not know how to turn the smoke on/off efficiently such that when it is "off", render time is fast (I don't want to just set the material to nothing, because the physics simulation will then still take up a lot of time).

Does this answer your question? Jet stream of water Only difference here would be density controlled by material. The best way now is to make it with Principled Volume.


text:
Help attaching skateboard to legs for character animation
I feel like this should be a bit easier as I've done this years ago in 3ds Max without the same trouble. What I'm wanting to do is model two legs (1 object), a skateboard (1 object), and an arm (1 object) for animation to import to Unity as ONE character mesh for an fps controller. I downloaded all of these meshes from free 3d model sites and posed them together and saved the Frankenstein as one model.
My trouble is when I animate them together in Blender (for an ollie animation) it looks great but when I import the FBX to Unity the board is in one place, the legs and arms are in another and the animations are all split up separately between each mesh, with no one animation showing the whole thing. I rigged bones for the legs object, then bones for the arms object, but did not put bones in the board because I don't need it to bend or deform at all (just spin and rotate and go up and down as one whole object). I tried adding one bone to the deck of the board but when I weight paint and try to pose the bones it only takes the deck of the skateboard with it and not the trucks or wheels. When I animate it all, using pose mode for the arms and leg bones, and object mode for the board, it seems to work fine (even great) in blender.
When I export to Unity everything goes to hell. There's about 95 separate animations that show up. They seem to be all separate pieces of the meshes from the "Action to be linked" part of the blender action editor which has the "fake user/users" buttons but I'm pretty new to Blender and especially new to Blender 2.8. In Unity only about 5 of the 95 separate animations for this one fbx actually show movement but none of which show all of these objects animating at the same time like it shows in Blender.
I've been searching forums, google and youtube for a week now and not sure where my problem is. Should I attach all of these separate objects together before rigging and/or animating via Join or Parent? Do I need to make bones for the board (even though I don't want to manipulate the mesh of the board at all)? I've tried parenting the board mesh to the leg bones and reanimating but it hasn't helped. The board always seems to be the most deformed and out of place in Unity. The animation seems great in Blender and I hope I'm just some clicks away from being able to fix this without reanimating but I'm starting to feel like something went wrong along the way.
Can anyone point me in the right direction? I've looked at attaching guns to hands but I don't need the skateboard to necessarily be attached to the legs when animating the jump as I'd like it to flip and legs catch.


text:
Render settings for 2d animation in Blender 2.8
What are the best render settings for a 2d animation comprising of flat geometric shapes in Blender, either 2.79 or 2.8? I have tried various things in both and the results are poor with the shapes stuttering across the screen. Any suggestions very welcome.

Never had that sort of problem with 2D animation. Please provide examples. What output settings are you using? Try a very small render size for quick tests e.g. 640x480 just to see speed etc.

Thank you for your comment, I'll try a small version as you suggest.

Meanwhile, here is a link to some test files with my original settings  https://www.dropbox.com/sh/mo49331n7uuz94x/AADrSv0pTZo-STdic8ENdPSoa?dl=0  Also, someone suggested the following settings which I tried but with no improvement:     File Format - FFmpeg Video.
Container - Matroska
Video Codec - H.264
Output Quality Perceptually Lossless
Keyframe Interval - 1

Okay, I've tried rendering at  640x480  - its not a great result either.  I've uploaded the files to the link above.

I am not seeing any stuttering in the video you just uploaded or in the results from the .blend. If you are talking about the image quality then you can increase the Output Quality to Lossless.

I've just realised that when I play the movie file online from drop box, the result appears better than when I play the file offline, though it isn't consistent. Any idea why this might be?

no, what is the player on your local machine? I use VLC

Its an open source player called 'Videos'.  I've also played it on someone else's windows 10 computer using the default player (not sure what it is called these days) and had the same issues.  Perhaps I should try with VLC

I always recommend VLC, works with just about everything. Watch out for dodgy download sites, https://www.videolan.org/vlc/


text:
Where are the custom images of the asset data preview stored? (Python)
I'm trying to figure out in the API where the custom image of a material in the Asset Browser, but I can't figure out where it is stored.
Note: I'm not talking about the image rendered by Cycles, but rather an image that I loaded manually through the operator bpy.ops.ed.lib_id_load_custom_preview()
I would have expected to find the preview stored in some property like this:
D.materials['My mat'].asset_data.preview
Unfortunately it seems difficult to understand where it is stored, and whether it is possible to obtain it via the python API.

TL;DNR: Looks like another incomplete part of the asset browser Python API.
It's definitely not in the asset data and there doesn't appear to be an asset op that accesses the information.  I think it's yet another part of the Asset Browser that  currently doesn't have an API.  The only thing I could find relevant was this addon for creating custom snapshots. It validates your assumption about how to read the data; but doesn't appear to use the existing data before it creates a new image.


text:
Problem with the bake result, how can I fix it?
I really don't know what I'm doing wrong, but I haven't been able to do a simple Bake for a day. In this example I have 2 materials on the same object. I mapped with UV mapping, copied the object, and applied the material to the copied object, making the copied object diffuse the bake result of the first object.
Obviously I inserted a "Bake Diffuse" image in all 2 materials on which I have to bake with the relative selected nodes, as per practice.
The result I get, however, is strange.
I am using Blender 3.0.1
I leave the original file for sharing here:
Bake Test.blend

Look at your UVs for the object that is supposed to receive the bake, the faces are overlapping, so what happens is that the bake for a face appears on another face. What you need to do is unwrap your object again, for example with the Smart UV Project mode.


text:
How to get the applied material on Surface/Curve Object type with Python?
I would like to understand if it is possible to determine and how, through Python, which of the materials of the ob.data.materials is really applied to the object of type Surface/Curve
This is my example The Brick material is what you see, while the other (Mat in this case) is not applied but is in the ob.data.materials
I would like to understand through Python how to check which material is really applied

I think you could go through splines and check its material index, something like ms=[s.material_index for s in ob.data.splines] should return a list of indices and show how many times a material is used... then check how many slots you have and delete those that are not in the list... and I think you need to remove them backwards, from last to first

Hey, that's it, yes it is! I think we can work in that direction. I am used to Mesh type, it is the first time that I try on objects of different types. I am not very familiar with the APIs of those objects. Excellent suggestion to continue my work.


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Call Handlers Function when installing the addon
I would like to run a function once the addon is installed, I don't know if it is possible, but it would be interesting to understand how to run this function only once.
I've tried calling some functions from the register() function but there are things in it that can't be done at that specific time.
It would be nice to run a function like, on_addon_installed_post

as a "cheap" workaround you could - if somebody starts your add-on for the first time, write a file which changes e.g. simple a text from ONE_TIME_CALL_WAITING to ONE_TIME_CALL_DONE. And you can check whether this text file has already that content

It is not possible to run a function at install time.  (see userpref.py) because there is no install time hook.  What is an example of something that can't be done at registration that you want to do?  Perhaps there is an alternative to a run-once.

There may be other solutions, this could be one of them.
When Blender is opened or addon is activated, the current time is compared with the installation time of the addon. For this we need modules addon_utils and datetime. First is not in API. Look at BlenderDefault/scripts/modules/addon_utils.py
Less than 1 minute is considered new in this example. The disadvantage is that you need to activate the addon for the first call within 1 minute.
bl_info = {
    "name": "first call test",
    "blender": (2, 83, 0),
    "category" : "All"
}

import bpy

def first_time():
    print("\n...check addon")
    import addon_utils   # not in API
    from datetime import datetime

    for mod in addon_utils.modules():
        if mod.bl_info.get('name') == 'first call test':   # get module

            time_mod = mod.__time__                         # get mod_install_time as timestamp
            time_now = datetime.timestamp(datetime.now())   # get actual_time as timestamp

            print("Modul:", time_mod, datetime.fromtimestamp(time_mod))
            print("Now:  ", time_now, datetime.fromtimestamp(time_now))

            if (time_now - time_mod) / 60 < 1:              # difference less than 1 min
                print("i am new")
            else:
                print("i am old")

### REGISTRY
classes = ()

def register():
    from bpy.utils import register_class
    for cls in classes:
        register_class(cls)
    first_time()  # testcall

def unregister():
    from bpy.utils import unregister_class
    for cls in reversed(classes):
        unregister_class(cls)

if __name__ == "__main__":
    register()


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How Change StringProperty Subtype with a Button?
The Blender API Allows you to create a property to insert a "Hidden" text useful for example to use for Password. This is possible by entering a parameter subtype='PASSWORD' like this, declared in the addon preferences:
password: bpy.props.StringProperty(subtype='PASSWORD')

Then to display in a panel:
layout.prop(preferences, 'password', text = "Password")

I would like to also be able to show a button to make show / hide the password, but I really don't know how to do it, since that property seems to be declared when Blender starts.

Possibly the easiest way to do this is to declare another prop without and swap them, rather than re defining the property, which is AFAIK the only way to change any of the attributes.  Comes up with min and max a lot.

Hello @batFINGER It would be nice to see an example. I think it might be a valid answer to my question.

Just declare two string properties and one bool, in your layout display one of the string properties based on the bool property, should be pretty straight forward right?

@brockmann I think it's that simple, but you should correctly update all 2 properties every time you change 1 or the other, relative to the subtype password and the non-subtype password.

get(), set() @NoobCat?

@brockmann Definitely a smart way, but I think it can be useful for the community to see a practical example.

Why waiting for it? ;) @NoobCat

@brockmann Because I've never quite understood get / set method, and I'm not sure how to do it in this case (I feel part of a fairly noob slice of comunity)


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Multilple Images Texture
how can i add another layer of another image texture(in this case a PNG image) onto an object that already has an image texture on it?
for example: i use a plane as a floor and it has a wooden texture on it but now i want to add a dirt PNG on it as well.

Hint: mix color node.

In order to do that , grab those image textures and mix those with a mix rgb node . Then set the mix mode to multiply and factor to 1. In case it's a png image then don't forget to use alpha as factor. Alpha value won't work in eevee . So set the blend mode to alpha hashed.
Hope that helps.


text:
Blender seems to extend invisible keyframes in the animation timeline
I'm trying to do a simple idle animation...I click on frame 1, insert location/rotation.  Everything seems fine.  I move to the next frame...say 10 frames ahead and move the hips down slightly.  Auto key frame is added...but when I scrub, I can see that the position I just set doesn't actually end up in that location until another 10 or so frames.
I have middle clicked down to scroll the frames down, I have clicked the home button while in the timeline but Blender won't end the animation on the current keyframe.  Instead it extends it beyond where there are any keyframes and I can't see them to re adjust them.
I've even tried multiple versions of Blender but it keeps doing the same thing.  I'm sure it's me doing something dumb but I can't figure it out

OMG...I had "Time Remapping" enabled.  I had it set from 100 frames to 250 frames.  Guess I don't know how to properly do a loop.


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Is it possible to capture a shadow on an emissive plane?
I understand the absurdity of my question, but I'm curious to know if it is possible to do this (On Cycles, and Eevee)
Basically, the plane captures the shadow, if the material is not emissive.
But I would like to make the plane emissive and at the same time capture the shadow,Avoiding the use of any shadow catcher
Plane with material not emissive:

Emissive plane (Without shadow obviously)

I can think of a way to do it in Eevee, but not Cycles. In Eevee, you can extract the color generated by a shader using a Shader to RGB node. If you connect this node to a Diffuse shader and a ColorRamp, you can get a shadow mask.

I think this is very useful, but it has a problem, as far as I'm concerned, this has a problem which is the change of light, with each added or removed light, or with the change of intensity, the points of the color ramp will have to be adjusted. However I think this answer can be very useful for many users

Sorry for the late vote, I will put this as the correct answer, although I was undecided, but I think that for the community, it is the best answer (This remains my opinion based on the various tests I did) It seems to me that this solution is the most reasonable of the various answers.

Use Principle BSDF shader for all material if possible.

I know there is a bunch of parameter which seems terrify. But they all do the perfect effect when you render it in Cycles. If you set the emission low enough you could see the shadow again. And if you want to adjust the strength of light, just add other color management nodes (Anything that you can output 3 value, R G B) to connect with the socket.

Update
If you don't want to enlarge the light difference between emit mesh and other light setting, you can use input: light path::is Camera Ray to filter your emission strength:

A color management node? Out of curiosity: How do you get the shadow? I honestly don't get any shadow when setting the emission value to 1 which is usually the case like when using images as planes add-on.

@brockmann I add a sun light to the scene if you see carefully. I don't understand why emission node socket use a default color chooser, if the thing is light setting, the value can exceed 1. eg. use a Bright/Contrast when manually set the Bright value and see what will happen in the scene. The material will act like a normal emission setting as an area lamp

Interesting. Do you mind sharing a scene? Also, calling the Brightness/Contrast a Color Management node is slightly misleading, you should edit your answer.

You can manually input values higher than 1 in each of the R,G,B fields in the emission field of the principled bsdf shader. If it were a simple value slider, you would'nt be able to get colored emission. @brockmann : blend file

Thanks @Gorgious. Tested your setup using an area light and it's only working if the power of the light is set to an incredible amount (the reason why the sunlight is working by deault). I think the question is how to get the shadow on the surface like when using a diffuse shader. Can we trick it using the Light Path node?

@brockmann Yeah, I don't meant to mislead anyone but that color node in Blender GUI is actually misleading user, there should be a new color node that could handle light as  well. The shadow is always there but only if the light strength is huge enough, then we can "see" the shadow in rendering. And light path is possible.

Thanks for the update. But... again there is no Color Management node @HikariTW

But those node is inside the category of Color

Can't see it: https://i.sstatic.net/IVTKg.png @HikariTW

what should I call them?

Depends on which one do you mean...? @HikariTW In a broader sense: Color correction or even color adjustments might be better to avoid confusion IMHO.

@HikariTW I think this can be a good trick

There is a simple way to do this using compositor. But you will need a shadow catcher.
First (in cycles) position your camera -> enable shadow catcher in object visibility -> enable the transparent option in the render properties and render it out as an image and save it
Now uncheck the transparency( if you want), disable shadow catcher(Now you may add emission), and then disable render output for your cube and render it out as an image(save the image).
Now go to the compositor and add the nodes as shown in the image

Now play with the color ramp sliders to get the desired shadow darkness

Consider that the shadow catcher does not preserve indirect light values.

The OP said: Avoiding the use of any shadow catcher

you can get shadows without shadow catcher but once you increase the emission shadow will disappear. I did mention I'll be using the shadow catcher to achieve it. This might help him to achieve what he asked for.

I thank you for this useful clarification. Unfortunately I wasn't going to work with the compositor, I need to work in real time


text:
Why does the "Checker Texture" node produce flicker with "Texture Coordinates Object"?
What you see is a simple plan with no double faces, checked and I'm sure.

This happens only when the mesh is at the local coordinate Z-0 height, if I move the mesh in edit mode, the flicker disappears

I'd just like to know if I'm wrong, or there is a problem.
This with the "Brick texture" node does not happen, for example.
I'm using Blender 2.83 but it seems that even with 2.82 the problem is the same

That's simply because your plane is between 2 checkers.
The checker texture is a 3D texture which alternates also in the Z axis. If you go in edit mode and move your plane up and down you will see that.
You can also rotate it to get different patterns.
In "Generated" coordinates your plane is in the vertical middle of a checker. That's why there's no artifact there.


text:
How to set Active and Selected Object into another Scene?
Let's start from the idea that setting Active Object and selected objects, within the current scene is possible through:
ob_1 = C.scene.objects['ob_1']
ob_2 = C.scene.objects['ob_2']
ob_3 = C.scene.objects['ob_3']

active_object = C.scene.objects['Active']
my_object_list = [ob_1, ob_2, ob_3]

for o in my_object_list :
    o.select_set(state=True)

context.view_layer.objects.active = active_object

Now, let's say we want to set the same objects that are also in a scene that is not the context one,
for example they are in "Scene 2", how can I do this without having to necessarily pass "Scene 2" as the active scene?

Just like with the context example, you have to set the active object via the view_layer attribute of the scene. Pretty straightforward.
import bpy
from bpy import data as D
from bpy import context as C

# Mannequin_01 & 02 exist in one scene, Monkey_01 & 02 in the other
# both scenes 02 is the active & selected object

set_obj1 = D.objects['Mannequin_01']
set_obj2 = D.objects['Monkey_01']

scene_01 = D.scenes['Scene']
scene_02 = D.scenes['Scene.001']

vls_01 = scene_01.view_layers
vls_02 = scene_02.view_layers

for layer in vls_01:
    layer.objects.active =  set_obj1

for layer in vls_02:
    layer.objects.active =  set_obj2


text:
How to remove an object from a scene with Python?
I have an object that I would like to remove:
my_obj = bpy.data.objects['my_obj']

I have 2 scenes:
my_scene_1 = bpy.data.scenes['my_scene_1 ']
my_scene_2 = bpy.data.scenes['my_scene_2 ']

The my_obj is present in both scenes.
I would like to remove my_obj from my_scene_2, which is not necessarily the context scene and I would like to avoid my_scene_2 becoming the context scene.
Obviously the my_obj must remain in the my_scene_1
I would like to avoid using Blender operators

Hello ! I think it should be clarified in the question whether you want to remove an object from a scene's objects or from a scene's collection's objects. Scenes can only contain objects directly through their main collection : scene.objects. However if the scene contains a collection that contains objects, these will appear in scene.all_objects but not in scene.objects.

bpy.data.scenes["my_scene_2"].collection.objects.unlink(obj)
Scenes contain all their objects in main "Scene Collection". If you unlink from that it should be removed.

If your object is present in both scenes, it means they are linked. Removing from one scene will remove from another as well.
to remove the object
import bpy

my_obj = bpy.data.objects['my_obj']

bpy.data.objects.remove(my_obj)

Hello, I don't think the first sentence is true, can you elaborate on why one can't unlink an object from a scene without unlinking it from another one ?


text:
Is it possible to change the active bl_category with python?
Assuming that the bl_category has a name, and is listed together with "Tool" "View" "Item", which are natively exposed in blender
in the bl_space_type = "VIEW_3D"
Is it possible to have a list of all the applications that are exhibited in this space? And is it possible to change the currently active tab via a script?

Search registered classes.
To get all the classes in bpy.types that are a subclass of bpy.types.Panel and bl_space_type == 'VIEW_3D'
>>> for p in dir(bpy.types):
...     cls = getattr(bpy.types, p)
...     if (issubclass(cls, bpy.types.Panel)
...         and getattr(cls, "bl_space_type", "") == 'VIEW_3D'):
...             p, getattr(cls, "bl_category", "No Category")
...
('CYCLES_VIEW3D_PT_shading_lighting', 'No Category')
('CYCLES_VIEW3D_PT_shading_render_pass', 'No Category')
('TOPBAR_PT_annotation_layers', 'No Category')
('TOPBAR_PT_gpencil_layers', 'No Category')
('TOPBAR_PT_gpencil_materials', 'No Category')
('TOPBAR_PT_gpencil_primitive', 'No Category')
('TOPBAR_PT_tool_fallback', 'No Category')
('VIEW3D_PT_active_tool', 'Tool')
('VIEW3D_PT_active_tool_duplicate', 'Tool')
('VIEW3D_PT_annotation_onion', 'View')
('VIEW3D_PT_collections', 'View')
('VIEW3D_PT_context_properties', 'Item')
('VIEW3D_PT_gizmo_display', 'No Category')
('VIEW3D_PT_gpencil_draw_context_menu', 'No Category')

... and lots more

Ok, lets recategorize  bpy.types.VIEW3D_PT_grease_pencil   from "View" to "Foo"
Check if it's registered (should be since it is in bpy.types, unregister it, change the category, re-register.
>>> cls = getattr(bpy.types, "VIEW3D_PT_grease_pencil")
>>> if cls.is_registered:
...     cls.bl_category
...     bpy.utils.unregister_class(cls)
...     cls.bl_category = "Foo"
...     bpy.utils.register_class(cls)
...
'View'

Note this "trick" is used in some addons as an update on an addon preferences string property to recategorize panels
Inspect the module.
Similarly, since a lot of these are from bl_ui.space_view3d can inspect the module
>>> import importlib, inspect

>>> for name, cls in inspect.getmembers(importlib.import_module("bl_ui.space_view3d"), inspect.isclass):
...     if name.startswith('VIEW3D_PT'):
...         name, getattr(cls, "bl_category", "No Category")
...
('VIEW3D_PT_active_tool', 'Tool')
('VIEW3D_PT_active_tool_duplicate', 'Tool')
('VIEW3D_PT_annotation_onion', 'View')
('VIEW3D_PT_collections', 'View')
('VIEW3D_PT_context_properties', 'Item')
('VIEW3D_PT_gizmo_display', 'No Category')
('VIEW3D_PT_gpencil_draw_context_menu', 'No Category')
... and many more

be remiss not to mention, most blender modules that register classes, have a classes list or tuple
from bl_ui.space_view3d import classes

for cls in classes:
     ... as above

or for every addon ... addon_utils.modules() provides a list of addon modules, that can be inspected as above to look for more, that may not even be enabled / registered.
AFAIK it's not possible to set the active panel / category (tab)


text:
Brick texture - controlling the randomness
I'm looking to create a brick like texture, but with 3 different 'subtextures', so much like in this question: Brick texture with multiple colors . However my problem is that I would like to have (statistically) the same amount of bricks of each color. So the color ramp approach doesn't work for me, because if I have (say) 3 different brick colors, they are chosen randomly from a range of 0-1 and if I set break points in my color ramp at 1/3 and 2/3, then there is no guarantee that out of my 3 colors, one is in the first interval, the second in the second and the third in the last. So that may cause my 3 colors to be reduced to 2 or even 1, depending on the random generator initialization.
Fundamentally I guess my problem is that I need to know the other colors that are used in the brick texture in order to know about how to classify each color, but afaik there is no way to get information for other pixels in each shader invocation (at least not in Blender Nodes). But maybe I'm just going about this the wrong way, because I'm thinking about this as a programmer and how I'd write this as an OpenGL shader. Probably what I need to do is change how I look at the problem, but I can't really figure out how.
I hope the way I phrased this question makes sense - thanks in advance.

OK well as usual, an hour after you ask you find the solution...
Turns out I was misunderstanding how the brick texture works - it doesn't generate a discrete set of colors, it draws a new random color for each brick. So each color is random across the entire color spectrum, and I can classify them using a ColorRamp after all.


text:
How to conceptualize a 'vector' in nodes-based shading?
I'm learning shader nodes. An important output/data type in nodes is the 'vector'. I know vectors in two senses (that are probably mathematically related, but practically distant enough to be thought about as separate I think): as in linear algebra (a 'thing' with direction and magnitude), and as in C++, a one-dimensional matrix or 'list' of values. How should I think about 'vectors' in Blender? They seem to be used as lists of values (e.g. a tuple of X,Y coordinates for the UV output of the 'Texture coordinate' node) but also as vectors in space, like for a normal. Or is a normal vector a list of length 3 with element 0 the X, element 1 the Y and element 2 the Z coordinate of the endpoint of the 'linear algebra vector', if that vector would start at [0,0,0]?

As a data type it's just a list of values.  Basically an array, but the language might provide it more features.  Perhaps the way to think about it is that it could be used in any of the ways you just listed.

I see, thank you.

One thing that tied me up in the shader tree is that it can be difficult to visualize the negative values you can generate.  Everything just shows up as black.  Absolute value or math -> add can help


text:
Drawing a specific color in the image editor
I'm trying to do something that seems very elementary but I can't figure it out: I want to make a 8x1 px bitmap and give each pixel a specific value in the Blender image editor. My first problem is that I can't resize the brush ('Draw' tool) small enough; it's always bigger than 1 pixel so I draw on other pixels. Secondly I can't find a blend mode that will just assign the color that I chose in the Color Picker; it always adjusts the existing color.

I think your falloff should be adjusted. Mine stops after radius 1 (2 is the diameter)
I was able to paint pixels successfully without modifying other pixels. Let me know if you need the blend file.
Cheers!

Ah I see, yes after some fiddling I now understand how it works. Thanks!

(for anyone trying after me: it solves both aspects of my question as long as the falloff is steep enough; I put mine at a full drop about midway, that makes most sense to me conceptually)


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3d cursor on position of vertex of subdivision modifier mesh with 'adjust cage' on
I have a mesh with a subdivision modifier and 'adjust edit cage' on. Now I want to move the 3D cursor to one of the points on the mesh so that I can insert a new object at the location of that vertex. However when I select the point, the center of the gizmo is a bit away from it (it's at the location where it would be if 'adjust cage' were off, see left image) and consequently when I move the 3D cursor to the selection, it's put not on the vertex but a bit away. The right image below is when I turn the 'adjust edit cage' off.
So is there a way to put the cursor at the location I'm after? Thanks.

Hello :). Unfortunately, gizmo currently doesn't take modifiers into account. The answer by R-800 seems like a good workaround.

One way would be to duplicate the object in Object Mode and then, for the duplicate only, apply the Subdivision Surface modifier. Then, snap the 3D Cursor to the desired vertex on this new version of the mesh. Afterwards, either hide the new version of this mesh, or, put it in a new collection so that it can be referenced at will in the future for this same purpose. You could also delete it if you know you don't need it anymore. But you now have your desired 3D Cursor position, and you still have your original mesh with a Subdivision Surface modifier that remains unapplied.

Ah I see, I thought this would be an obvious thing I had just missed how to do. Thanks.


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How to show only selected strips on dope sheet in VSE?
I'm using Blender 4.0.2 on Windows 10.
In VSE, I would like the dope sheet to display only the keyframe data for the selected strip(s), but it shows all the data for all the strips. It's very messy and hard to use.
I know that pressing [.] on the numpad moves me to the selected strip, but still sometimes, especially when a few strips are selected, the keyframe data is spread out so much that I have to hunt it down.
See image below. Thank you :)
Maitrisingha

try selecting your strip and then shift-h

In the dope sheet, try enabling the "Show Only Selected" filter:

It's enabled by default.


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Grease pencil onion skin not showing in draw mode 2.81 but works fine in 2.80
What am I doing wrong?
Using 2.81 Windows 10.
Onion skins do not appear in draw mode, but they do appear in edit and sculpt.
When I load the same file into 2.80 the onion skins appear in draw mode.
As you can see (top image) Onion Skins are checked in Viewport Overlay, and the layer (Mr C) also has onion skins checked, so too are they checked in the materials tab.
And in Blender 2.80 opening the same file (bottom image) the onion skins show.
When I open up a new blank file in 2.81 and draw with grease pencil the onion skin works fine in draw mode.
Here's the .blend file
Thanks.

I realize this is an older question, but I found this while having the same issue. I discovered that for me the problem was that I was in the render preview viewport shading mode. Onion skinning worked in ever viewport shading mode except that one. Hopefully that helps someone else.

Go into the Show Overlay option then check the box saying onion skin tool.

I want to promote this as I have a similar issue, except that in no modes can I see the next and previous frames for my main Stroke. If I create a new Grease Stroke, then it works as expected. I believe all the required onion skinning options are also selected.
My Blend file is

Answer 2 For my issue, as suggested by Maitrisingh, was that the Material Properties also needed to have onion skin selected.
Answer 1 For the original issue, try this: Only have the one 3D viewport open (may be a bug having 2 open), go to Sculpt and then go back to Draw and it then started to work for me. Hope this works for you.

The reason your onion skins don't show is that you have some onion skins unchecked: Look in the Object Data Property tab, where 3 of the 4 layers have onion skins unchecked (Body, Arm & Hand and Eyes Fill are unchecked. Only Head is checked). And in the Material Properties tab, your Lines and Eyes are both unchecked. :)

Thanks @Maitrisingha - The Materials Properties was the problem for me.

Hooray! Thanks Derrick. I shouted out loud when it worked. And if I then reopen a second viewport window it still works. Glad we could help each other across such a distance! ;)

There is a small button in the 3D view header during Draw Mode named Multiframe. When it is active you can't see the onion skin.


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PNGs in distance appear to overlap foreground PNGs when viewed at different angles
Unless I'm doing something wrong, I think this is a bug.
Large PNGs imported as planes render strangely in both the viewport and final render (Eevee). I had this same issue in 2.80 and now using 2.81. Using Windows 10.
When seen face on (top image) things look good but when the angle to the plane is tighter (2nd image) you get distant PNGs which are technically behind objects appearing in front of them.
Most of these PNGs are 30,000 pixels wide, with an alpha mask.
I use the add-on import images as planes, and import with Emit setting (see shader node settings below). Blend mode: alpha blend.
I've uploaded a short video here. You can see the problems starting from 20 secs. Before then everything is fine.
Thanks.

Does the effect change if, at the first  problematic frame, you change the near / far clipping distances on the camera?

Tried that already thanks. No difference.

The reason is that the "import image as plane" addon sets the material Blend Mode to "alpha blend" by default. Switching it to "opaque" resolves the issue.

How to solve this with "alpha blend" on is also open in my related question: Plane-object displayed in background while beeing in front (Eevee Viewport)

Thanks. I can't use opaque because each PNG has an alpha mask. But you were close! I changed Blend mode to alpha clip, and it worked. I still think it's a bug, but this will do.


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Grease Pencil colours appear darker than Base Colour (lights are off)
I'm trying to draw simple light blue strokes in Grease Pencil (Blender 4.0.2)
They appear duller/darker in the preview, the viewport and in the final render. Lights are turned off. Is this a bug? Or am I missing something?
Paint mode: Material
Thank you,
Maitrisingha

Really can't say what the issue is. Perhaps you can recreate a sample to post with your question using https://blend-exchange.com/?

I never really noticed before, but yes default Blender does this. It's not the grease pencil, it's the render settings adjusting your colours slightly.
I believe it's because your View Transform setting is most likely set to 'Filmic', setting it to 'Standard' should fix the problem.
Go to your render settings, then Colour Management, it's in there, hope this helps!

It worked. Thank you so much, where ever you are in the world! How strange that filmic is the default. Can't complain. Blender is excellent.

Hey no probs, I'm not an expert on this part but I believe it's the default because it's better for photorealism, and if you're using blender for 3D then mostly people want to make a lifelike object or characters, but for grease pencil it's a bit ehhhh, Filmic crushes the colour range to be more realistic apparently.


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How can I remove that line on a kind of spheric form?
I wanted to make a grape and the result is not bad but I have that line which kills everything. Does anyone know why it appears like that?

I used mix RGB with the option Color Dodge

Did you use a mirror modifier?

No, I used subdivision and displace

Are you using UV's to map the procedural textures?

maybe a normal problem? maybe show your whole node setup or share your file: https://pasteall.org/blend/

Here is the file: https://pasteall.org/blend/92155cb2cef14596849d4e96ede7bfa1

I am pretty new in Blender so for me it's still relatively complicated to understand fully

Try using the generated or object coordinates and lower the scale of your noise textures. The seam is caused by your UV seam. Alternatively you could design your shader so that it is seamless (more complicated)

I used generated and it worked !!! Thank you so much :)


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My glass becomes opaque on the bottom
I made a wine bottle for a client and when it's turning it becomes opaque at the bottom, really strange and I do not understand why. Do you have any idea ?

Any chance you have a second (hidden in viewport) mesh that's showing up in the render?

No unfortunately. I have a plan under which is rough and makes it appear even more

Please use the [edit] link at the
bottom of your question (https://i.sstatic.net/lXFuK.png) and add
more information on how you set up your material. Please add an image that shows the nodes and the outliner.


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Why do I get this glass result?
Pretty strange that I get this glass result. I am making a a wine bottle so nothing too complicated. I think I will do my model again, but I would like to understand what makes the model being this unrealistic? I tried to play with a lot of settings, I followed advanced tutorials but even then nothing made sense. Here is the file yo ucan download : https://pasteall.org/blend/a9482823b5024548ae168368464bef96

Looks like bad geometry to me. Try to clean it up in the first place, by removing any duplicated vertices -> Edit Mode > Mesh > Clean Up > Merge by Distance and make sure your normals are pointing in the right direction.

It helped a bit but not completely. It seems that my model is a complete mess with the normals. So I did it again. Thanks for the support !

That looks like overlapping faces, probably duplicated or so close together that they create z-fighting.

Thank you so much ! It worked !


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Boolean do not function while trying to make a mold
I am trying to create a mold by doing a boolean from a Nike sneakers. My goal is to then print the mold in 3D later on.
The problem is that the boolean don't work (and the model I took is empty).
Do you have any idea how I can fix that the more efficiently?

please provide blend file...but you can try to change between fast and exact. One works.

Thanks! that worked, it's not the best practice but your solution worked. Thank so much

you are welcome. Happy, i could help you.


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Python script that takes xyz and returns the perspective matrix vertex coordinates
I've been trying to write a script that receives the xyz coordinates of a vertex of a 3D object and returns the xyz coordinates of the vertex in a prespective projection plane, more or less like in the following image:

Example:
get_prespective(3,4,8):
     bla...
     new_vector = [3,4,0]
     return new_vector

Supposedly you need to multiply the vector with a prespective matrix, like this:

Or multiplying the vector by this matrix:

But I'm having some trouble figuring out which matrix to use or how to use it. If somebody has a better idea, that would be great ;)

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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Is it possible to place images and videos on sides of moving geometric figures in Blender?
Here is the example of animation https://www.youtube.com/watch?v=ekWu57GI38I&t=271
From 4:31 till 4:38. Animated background. Infographics over it. I focuse the attention on animated background. There are geometric figures. Parallelepipeds. They move. I want to make similar animated background. Not one to one to this. I will use other colors, other sizes, other direction of move.
I will make parallelepipeds. They will move. Slowly.
On sides of few parallelepipeds I want to place still images. Parallelepipeds will move. On sides of few other parallelepipeds I want to place videos. Parallelepipeds will move, videos on sides will go. Is it possible to make in Blender?

Yes it is possible. Try it.

@susu Thank you, susu. Which render engine to use in this case? Eevee? Cycles?

again... try and find out what works for you.


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Does Nvidia SLI matter for Blender?
Does Nvidia SLI matter for modeling in Blender, rendering in Cycles, rendering in Eevee?

No, leave it disabled. See: https://blender.stackexchange.com/questions/5228/how-will-multiple-gpus-improve-cycles-rendering-performance

@DuarteFarrajotaRamos is that the case for eevee as well?

https://blenderartists.org/t/eevee-sli-crossfire-possibilities/1158208


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Do I need to optimize PNGs after I will output them from Blender and before I will import them to video editing software?
I want to make animation in Blender. It will be transition for video. In video editing software I will put this animation over junction of two parts of video.
In Blender I will make output as PNG sequence. Next step I will import PNG sequence to some video editing software. Maybe OpenShot, Shotcut, Kdenlive, DaVinci Resolve. Maybe some else.
Do I need to optimize PNGs after I will output them from Blender and before I will import them to video editing software?

Never ever render to png. Render to OpenEXR: https://blender.stackexchange.com/a/106671/31447

@brockmann Thank you, brockmann. I took in attention your words. I took in attention the material you pointed. In https://blender.stackexchange.com/questions/106670/compositors-corner-pin-node-does-something-odd-to-input-image/106671#106671 troy_s wrote "their alpha values are unassociated by design". What does it mean?

@Konskoo Unassociated (straight) alpha offers less precision compared to Associated (premultiplied). This leads to ugly borders between transparent/opaque areas.  Wikipedia - Alpha Compositing

@JachymMichal Thank you, Jachym. I took in attention your words. I took in attention the information in Wikipedia - Alpha Compositing. I want to use more precision. Because of it I want to use associated (premultiplied) alpha. Does in OpenEXR associated (premultiplied) alpha set as default?

I’m voting to close this question because it is not about using blender.

@RayMairlot Ray, this question is about using blender. About output from Blender. I received many useful information from answers. And I want to clarify few details. I want to continue discussion in this question

No, assuming by optimize you mean with an optimizer such as pngcrush. These optimizers are designed to strip out extra information in the file in order to reach the smallest acceptable file size, which seems unlikely to matter much for files that will only be used while you're editing your video. If optimizing accomplishes anything, it'll be to optimize away information which might have been useful when making further tweaks in your video editor.
As brockmann pointed out in the comments, using EXR is preferable to PNG, if your video editing software supports it.


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Custom Blender Camera Shape?
Is it possible to have a custom Blender camera shape?
Like when rendering, the camera image outputs as a "triangle" shape? Or a polygon shape?
Is there a trick to making a custom picture shape without actually rendering a rectangle or a square?
The reason I am wondering is because this tutorial shows how to do it in OBS studio. So it might be possible to do in Blender.
If you know an answer, please share. I would really like to know.

Do you mean the shape in the viewport? Or some kind of clipping mask on top of the final image?

related: https://blender.stackexchange.com/questions/107326/how-to-create-a-circular-camera-safe-frame?rq=1

I think the holdout shader is what you want: How to mask animated objects so they aren't visible past a certain area?

NO. I want the camera to have it's own shape.

Hello :). Your video output will always be rectangular. The linked tutorial is using a circular clipping mask over the rendered rectangular video, which you can do using compositor.

Ok. Can you tell me how to do that? I'm not experienced with the compositor, and I would like to learn.

See link in comment of @brockmann

Your rendered video will always be rectangular.
But you can add a mask over it, using the compositor

Create a black and white image using Blender/Photoshop/whatever
Add an RGB node, using the Mix node
Connect your BW image into the FAC input

How to connect a mask in compositor.
The RGB node changes the background color.

Or you can use a holdout shader as mentioned in my comment, which also saves render time.


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Modifying keyframes for a mask created in the UV editor
I have created a mask in the UV editor and I've animated the movement of the edges of the mask with keyframes in the dope sheet. However if I switch to the graph editor I can't find my mask with the keyframe values of the position of the edges of the mask. How do I find these values?

I am not 100% sure, what you mean by "created a mask in the UV editor", because as far as I know the only way to make masks in Blender is in either the image or the movie clip editor.
But maybe I am missing something.
If you mean that you want to animate an edge of the unwrap of an object, then the short answer is that Blender cant do that.
A really quick google search unearthed this addon, though: https://www.blendernation.com/2011/11/12/animating-uv-textures/
If you are already using it and are wondering why these properties still dont show up in the graph editor, you should probably try to contact the developer directly.

Yes, I meant the UV/Image editor window.


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Make a meta strip show the audio waveform
I have a meta strip which contains a video file and an audio file. I can clearly see the waveform in the audio file. However if I create a meta strip out of these two strips the audio waveform disappears. How do I create a meta strip which shows the audio waveform?

As of blender 4.0, there is no current built in way to show the audio waveform on a meta strip that has an audio strip within it.


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How to change the background colour in the Material Preview window?
If I want to change the colour of the sphere in the Material Preview Window, it's easy enough to create a Material Output node, Create a shader node, assign a colour and hook them up. The sphere colour changes accordingly.
But how do I change the colour of what's in the background, behind the sphere?
Moreover, what does that colour represent? In my example it's Magenta and I don't know why.

Usually there is a checkerboard pattern behind the sphere. And that looks like the color that usually indicates a missing texture in the 3D viewport. I don't really know but It makes me think you are missing that image somehow.

It seems that I somehow chose a colour (or texture?) in Blender that is impossible to display.  The same magenta colour shows up in GIMP when selecting an impossible colour combination, as per this answer: https://graphicdesign.stackexchange.com/questions/125622/when-i-try-to-change-a-color-everything-become-purple


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Numerical value of keyframe in the Graph Editor
I'm manipulating animation keyframes in the Graph Editor in Blender and although my keys are clearly marked "Value", I can't see exactly what the value of this key is ; I can only eyeball its location by manually moving the keyframe up and down the Y axis in on the graph.
I would like to manually set the height of the keyframe in the Graph Editor by inputting a numeric value. How do I do this?

Select the keyframe in the graph editor.
Press N to open the properties panel. Go to the F-Curve tab and the Active Keyframe section. You can read and write the keyframes Frame and Value.

Show Sliders
From the graph editor view menu toggle view sliders

Now each fcurve has a slider in the channels region.

When the scene frame is on a keyframe, highlighted yellow, updating will change the keyframe value. When green, will add a new keyframe at that frame.


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Why is this happening to my subdivided holes in my cylinder?

I've used Shift-E but i still get glitches. I need subdivision surface for my whole other part of the mesh and it works fine there. It's a weapon so I need detail.

https://blender.meta.stackexchange.com/questions/2449/what-is-the-problem-with-posting-an-image-or-link-and-asking-how-do-i-do-this

Try to add edges like on the picture. But anyway this is a bad topology, you need to learn about it.

Brief The Answer with clear Method.

I've done that before and it ruins the cylinder. It makes it bumpy. How do i make better topology?

Use this topology reference https://imgur.com/r/animation/dEWXP to make your topology better. And remember that using booleans for subdiv modeling is a bad idea.

I did it another way, i'll have to live with some visible edges.
I used another cylinder, removed the face from one of the sides, made 3 loop cuts without moving them.
Got another cylinder, 90 degrees on the x axis and stretched them to fit in the cylinder. Selected all 3 and booleaned them with ctrl-f.
After that I used the solidify tool.
Moral is: dont extrude at the end of the cylinder as it will mess stuff up.

edited, sorry..

authors: Алесь Сиденко


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Texture and Color mixing
I need to mix 1 gray-white texture with yellow color.
Here is a model with a gray-white texture without the applied yellow color.

I was able to apply a yellow color through the nodes, but it does not appear in the render.

I need the same result, only to make the model yellow in the rendering.
please show me where I made a mistake =)

Try replacing the multiply shader with a mix shader

It's don't work

here is result
https://i.imgur.com/8i1wExb.png

Oh i done with this, using Principled BSDF.
https://i.imgur.com/HefBVtG.png

You cannot mix a color(or a texture) with a shader in Cycles. You are currently mixing a texture with a Diffuse BSDF shader - that's the problem. It will be enough to disconnect it and set the color directly in the MixRGB node to fix this.
If you wanted to have a separate node for the color for some reason(for example if you want to connect it to multiple inputs so you can change them all at once), you can use RGB node that you can find among Input nodes.


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Is it possible to render a file with combined CPUs of 4 systems?
I have four servers, each having 16 threads. Is it possible to render a single file using the combined power of 4*16 threads? Basically, I want to know whether different CPUs can render a single file simultaneously.

You might want to look at Crowdrender: https://www.crowd-render.com They are developing an Add-on for Blender which should allow for exactly what you‘re trying to do.

The thing is that, I cannot access blender's GUI in my server. I have to run a command from CLI as blender -b example.blend -o . If there is still a way to make use of crowd-render.com, It'll surely solve my problem.

Is it possible for you to use a fifth machine - like a laptop or something - as a master? It would provide the GUI part, the servers would do the number crunching. Crowdrender can kick off the render on slaves without using the master for rendering.

Other than that, it might be worth contacting them. Could be that there is a possibility for command line rendering somehow.

I should try contacting them,  @aliasguru . Thank u.

If it's a long render like an interior visualization with lots of indirect light and it takes hours to render it pays off to just split the samples in 4 parts, so if you need 20 000 samples you can just render 5000 on each machine with different render seeds saving them in EXR 32bit full float format. Then you need to combine everything mixing them proportionally - so you would blend each 2 of them with weight of 0.5 and then blend the results together with 0.5 weight as well in Blender's compositing so each of them contribute 1/4th to the result. Obviously if you are rendering animations that will be too much work so you would need to look into automating this with Python, but with animations you can just render different frames on different machines as well. There might be addons for automating this already that I am not aware of, so it is probably a good idea to search for them as well if manually doing this is too much trouble for you.

Since sampling in Cycles uses a stratified sequence rather than random samples, you may get better results border rendering 1/4th of the image with the full 20k samples on each machine, rather than rendering 4 full images with 5k samples.

Different render seed will make samples unique for each render. Even if there is a theoretical difference it will not be preceivable in practice. I think it is very safe to disregard this. I use the technique and I have compared combined renders with the same total amount of samples rendered once and it has allways been impossible to tell the difference even comparing them viewed one imediatly after another.

Thank you @MartinZ . Actually, I have a very little knowledge about Blender. A friend ask me to render a 2 minute video in my server. I should check this technique soon and get back.

In the case of animation you can just divide the amount of frames equally for each machine. That will require the least effort and will be fastest.

Really helpful. Not what I want exactly, but, the best technique I knew so far. Thanks. @MartinZ


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Scaling both an object and its position
Is it possible to scale an object and adjust its position accordingly?
I've got an annoying situation where the scene unit scale was 1.0 and I needed to change it to 0.001 for millimeters. However when I scale the objects by 1000 in the scene their positions don't adjust so they all end up on the center axis since the position locations become very small values. This messes up positions of objects used for boolean operations and alignment of parts (there are many objects to adjust).

EDIT: I do realize I could manually scale each of the position values by 1000, I'm hoping there is an easier way as there are around 100 objects in the scene

"their positions don't adjust so they all end up on the center axis since the position locations become very small values" Can you elaborate more in detail what this means? If you just scaled down and then up after that it should be the original again, right? So something must have happened inbetween. Also your gif is nice but not very helpful i fear. Where are these letters supposed to be, what booleans? Maybe you are just looking for this option https://docs.blender.org/manual/en/latest/editors/3dview/controls/pivot_point/individual_origins.html

When the 3D cursor is at the world center (0, 0, 0) and if you then select all objects and set the Transform Pivot Point to 3D cursor, scaling by 1000 will then also scale the locations outwards from the center by 1000.


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How to dupliframe several objects
I have a basic wall lamp made of 3 objects:
- a support
- a light bulb (emissive half-sphere)
- a Blender point lamp
I would like to duplicate this wall lamp along a curve.
I used dupliframe as I don’t want objects to be deformed along the curve.
I made the light bulb and the point lamp as children of the support, then the support as children of the curve. In the support object properties I used duplicate/frames. But only the support us duplicated, not the light bulb and the point lamp.
What is the right way to do this?
Thanks!

I think you need Group Instances


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isolating part of a mesh after boolean in geometry nodes
I've created a node tree that is able to separate a cube according to its planar symetries as in the image below
Now I would like to access geometry of one of the tetrahedron to perform some modifications that I will further mirror on all the other tetrahedron.
Anyone could help me on how to access one tetrahedron ?

You are probably better off doing the reverse workflow of creating a stand-alone tetrahedron with the desired shape then instancing it to form the cube, if you wish to propagate changes.

This approach is definitely worth a try. I found this topic for the symmetries : https://blender.stackexchange.com/questions/251877/geometry-nodes-how-to-mirror-geometry-along-normal

You may use the Separate Geometry node in combination with the Mesh Island node, to access separate parts:

Thanks. This is what I was looking for. I will conduct both methods (yours and the one proposed by  @Duarte Farrajota Ramos) to see what works best in my case


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Blender General Best Practices (to affect a game's performance as little as possible)
I've started modeling a few weeks ago by doing some anvils/random objects/humanoids and animations. It seems that for some of them I used too many unnecessary vertices (and perhaps modifiers) after instantiating loads of them on my Unity project.
I was reading this page where they share some basic tips to reduce a model's rendering cost but maybe you guys have some other useful links that you could share and/or general tips. For example, I know that we should start with a model with as few vertices as possible and from there model it and apply modifiers on top of it, but how "costly" are these modifiers?
Sorry if this question has been posted already but I couldn't find an answer that address my current problems. If there is, please leave it in here, if you don't mind!
Thank you so much!

Possible duplicate of Is there any clear definition of game-ready models?

Related https://blender.stackexchange.com/questions/115226/low-poly-modern-2018-standards/

@DuarteFarrajotaRamos Obrigado, Duarte. Much appreciated


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transparent logo on glass
I'm am making a bunch of liquor bottles and i have too much reflection on the transparent image on the outer part of the transparency.
My first material is the glass node,  my 2nd material is the transparent image on the section of the bottle I need it on.  I am thinking it needs to be all one material but i cant find the correct node set up if that is the case.
Do you have a node set up that will help him achieve less reflection.

Related https://blender.stackexchange.com/questions/52092/apply-texture-only-on-parts-of-object-with-nodes/

And one from me: https://blender.stackexchange.com/questions/79237/how-do-i-make-my-decal-non-transparent/79241#79241

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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Why does EEVEE take More time when it is rendered from the button than viewing in the actual viewport?
Why does EEVEE take More time when it is rendered from the button than viewing in the actual viewport? I mean when you pan around in the rendered mode in EEVEE it takes no time to render it to the viewport but when you hit the render button from the menu, it takes some time and renders it frame by frame.
Other than that im loving 2.8 and EEVEE...

just like with cycles, eevee offers separate quality settings for viewport and render. one of them is the sample count. another reason could be that your camera resolution is bigger than the viewport, so more pixels have to be rendered.

Thank you for the answer :) Can you guide me about adjusting the camera resolution to match the viewport's? and is it possible to pan the camera around using the the normal viewport pan around methods. I mean without selecting the camera first then pressing G and then moving it around. Thank you.

there is no way to magically match them. for rendering needs, one sets the output pixels as required. to manipulate the camera using viewport navigation, see cegatons question here https://blender.stackexchange.com/questions/68996/assign-shortcut-to-lock-camera-to-view

Because viewport sampling is lower even with eevee. Also, viewport has lower resolution.

This is a comment, not an answer. Answers usually try to give a more elaborate explanation why things happen. Please read How do I write a good answer? thoroughly


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I cant extrude in Z Axis
Iam attempting to extrude in Z Axis iam pressing E+G+Z but I can't extrude the plane.
I am following this tutorial: https://youtu.be/OHg-CHcflPM?t=1299.

Are you pressing the keys one after another or all at the same time? What exactly are you seeing on the screen?

I edited it now you can see what I see.

and one after other

Don't press G
The E shortcut is for the "Extrude Region and Move".

The move (or grab) command you are trying to recall with G is alredy active. So by pressing G, you are activating the Vertex Slide option of the grab command.
Just press E and then Z to restrict the movement because you are already grabbing the object around.
Or yuo can press E and then Esc to Extrude the region only. After that you can activate the grabbing with G and restrict the movement with Z.


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Group an object
I modeled some vehicles for a map and I still need to do a hitbox. I follow a tutorial on a website and there in mentioned:

"Note that each piece doesn’t have to be a cube, as long as it is
  convex (not having any interior angles greater than 180°. (picture))
  and a sealed solid. (...) Note that all parts of the collision mesh
  must be within the same model."

What do I have to do exactly, if all parts have to be in the same model and it is convex? Ctrl + J is not working because it then becomes one object.

If you have any questions just tell me. Thank you for help!

A quick glance at the article would suggest that the hitbox model is supposed to be one object, so Ctrl+J would be the correct way to join them. This will still keep each piece of the hotbox model seperate (they won't be 'fused' together) but will make them into a single object.

I tried it with that technique and its not working then (Control + J). I heard something about grouping objects. Is there a way to do this? But thank you for the answer :)

You can group objects with Ctrl-G, but from the article Ctrl-J will be the best way. What's not working for you?

Grouping only serves as a selection tool, and doesn't enable the group to behave like a single object. The parts are all separate meshes but one object when joined with ctrl + j

The hitbox is not convex when grouping all objects, so the program for the map (hammer) will generat a hitbox for it.

Have you tried joining the objects with Ctrl J and then following the rest of the tutorial? From everything I read, as long as each section of the hitbox object is convex, then everything should work fine. When two convex objects are joined with Ctrl J, they do not become convex, even if they intersect and the intersection causes the whole object to be convex in places.

Ok, I found the mistake! It was no problem with the model or the group. I just had to smooth the model complete! So I thank everyone who told me that the Control + J technique  should be right :P


text:
Distance between two Bezier curves
I have curve modifier applied on 3 extruded planes. The curves and planes all have the same width and the curves have the default handle values.
My expectation was that since the distance between the two curves throughout the curve extent is constant, if at one end the objects are just touching each other, at the other end also they would touch but not overlap.
I notice, however that at point 1 of the curve there is considerable overlap in the objects. Could you help me find the reason and the resolution of the issue.

"My expectation was that since the distance between the two curves throughout the curve extent is constant"
The distance is not constant, your curves are not parallel.
If indeed they are just three Blender default Bezier Curves objects, simply shifted up a certain distance on the Z axis, that doesn't make them parallel, and hence the distance between them is not constant.
The green curves below are all default Bezier Curve objects moved 0.1 units, and the orange ones are the truly parallel result for comparison.

For that to be true you would have to make an "offset" of the curve geometry which I've heard is technically not possible to do perfectly for Bezier curve based geometries, mathematically speaking.
It is also not trivial to accomplish in Edit Mode in Blender anyway, unfortunately. Either use the Offset curve property, in the curve Object Data panel, which is Object Mode transformation only, or offset your planes instead as HENDRIX mentions in his answer.

My thinking was: since y, or in this case z, is a function of t - a value that depends on the control points (i.e. handles) of the curve - if the control points have the same nature, z should vary proportionately along the curve. But maybe that doesn't necessarily produce parallel curves.

The "distance" between them may be the same in the direction of duplication (ie. global), but not in the direction of extrusion (ie. the normals of the curve).
One solution to fix this is using the same curve to deform all your planes, just give each of the planes the right offset in object mode.

Yes, offsetting might have been a good solution but the curves need to be parented to individual axis of rotation of the planes, so unfortunately that is not an option for me.


text:
Bone Constraint Copy Scale on multiple bones in chain bug?
I'm trying to make a chain of 8 parented bones stretch on the y axis using the copy scale constraint and a separate controller bone, but using it with more than two bones causes all the parented bones to scale infinitely. Logically, this doesn't make sense. if the controlling bone is scaled to 2, all the bones in the chain should be at a scale of 2. Is this a bug or am I missing something with parenting?

I didn't know about the inherited parenting, disabling that fixed the problem

You could turn this into an answer that would be more helpful to others it you add some more details. Example: what is inherited parenting. Where to find this setting.