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Convert particle system wont work properly : it modifies the geometry
I have a problem with the "Convert" button of my particle system : as soon as I click on the Convert button of the particles system modifier, my particles losses a part of their geometry (it is more rounded)
Here is the story (Apologizes if my english is hard to understand, I'm french, baguette) : I'm making asteroids belts.
So, I've created rocks affected by a subdivision modifier and a displace modifier with voronoi texture. Then I've duplicated it and scaled the rocks differently. Then, I've created a collection to put my rocks in.
Then I created a simple torus on which my rocks poped up thanks to a particle system. It is set as this :

I have plenty of particles system as this one, now I need to "bake" this into meshes (1 asteroid belt = 1 mesh).
To do that, here are my steps :

Select Torus 1 (first particle system, first belt)
Hit the Convert button on the Particle system modifier
Object -> Relation -> Make Single User (Object & Data) so that every particle became the single user of its modifiers (the subdivision and displace modifiers inherited from the rocks i've created earlier as a source collection for my particle system)
Object -> Convert to -> Mesh from Curve/Meta/Surf/Text
Ctr-J : Now I have a unique mesh for the first asteroids belt (then I decimate it but anyway)

My problem is : Once I clicked on the convert button of a particle system, every rocks loses a part of its geometry, like if the Voronoi Texture used for the displace modifier losen its effect.

How can I fix that ? I really need a strong texture for my scene.
By the way, the rock texture is just a noise node plugged in a bump node, then in the Normal input of a principled BSDF. So the displace modifier of a rock applies a Voronoi texture on it, then I bump the texture with a noise texture.

Which texture coordinates input are you using?

It is a simple texture coordinate node (Object output) plugged in a mapping node (Vector input). Then mapping node -> noise texture.
But again, is it a texture problem ? For me it is more about geometry, as my texture only applies a bump on the mesh.
In any case, I use the Texture coordinate + Mapping with pretty every texture I use. I'm a begginer, I usually use it to coordinate a texture with a UV Map. In this case I don't really think it is usefull but I put it anyway...
Here's a screen of the texture : https://nsa40.casimages.com/img/2020/09/01/200901054102901069.png

ok, is the displacement modifier set to global coordinates or local? I presume this is global... Set it to local. Because when applyed, the relative size is totally different.

When the particles are converted, they aquire their size as particle, so generally much smaller than the original object.
From that, if the displacement is set to "global" coordinates, the mapping of the object on the voronoi texture becomes very small and so has few variations.
As solution, set the displacement to "local" coordinates and the mapping will be equivalent between your original objects and the converted particles.

Alternatively, you can change (lower) the voronoi texture size once the particles are converted.

Ok it worked like a charm !! Sorry for my past comment I didnt know that you were asking for the Text Coordinate setting in the displace modifier haha
I had to set this setting to Local for every rock references (29 haha...) and then modify the Voronoi Texture used for the displace modifier, as it gave me a slighty rounder displacement with this "Local" setting, as you said. But after this, Blender managed to convert those particles in a mesh that is perfectly the same !
Thank you ! :)


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UV Unwrapping - All Maps Ruined (distorted)
So I was unwrapping for some big portion of my day today and all of a sudden all the maps that I so carefully have been portioning have changed their dimensions - it basically looks like they were never unwrapped. All I can think of is just before this happened I marked some seams around a cluster of faces. Not satisfied, I deleted some of its edges and made it into one big face. After that all maps using the same material in my scene were ruined.
No other faces that use different materials were affected.
I first undid as many steps as I could without result. I force shut the software and started up the project - looked just the same so I assume there is no way of saving all this wasted time and work.
I'm just wondering what the heck happened. It's not the first time I've had this problem.
How do I make sure that this never happens again?
Thanks,
Samuel

Drop a screenshot, maybe your . blend file with https://blend-exchange.giantcowfilms.com

You can make sure this doesn't happen again by pinning (shortcut key P) the vertices in your UV that are already in a place you like (and don't plan on moving).

Just have you checked File > Recove > Auto Save directory if there is not any undestroied? Also by default blender saves versions .blend1 .blend2 if you delete number it become regular file to open so there could be a chance?

source: Stack Exchange

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

sort: votes


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how to rig a car engine piston
i need some help setting up what is basically the same as a piston in a car engine's cylinder. i know i can just use keyframes and NLA strips but im after a more dynamic approach that wont require a bunch of edits to change the speed or phase. ideally i want to connect the rotation to the up and down motion of the control handle im using for the rest of the parts but i am stumped.
i have animation nodes installed so solutions using that are also viable. suggestions appreciated as im at my wits end.

https://en.wikipedia.org/wiki/File:Piston.gif

@AlienXtream.. if you're still having difficulty, post a minimal, stripped-down version of the mechanism in place on https://blend-exchange.giantcowfilms.com/, and I'll get to it.

@RobinBetts oh. sorry. didn't notice that comment till after i made a drop box file. im still new to navigating this site >.<

This can be done with one driver and one look-at constraint.
The height of the piston-pin above the center of the crank is given by the following expression:
h = r * cos(A)+sqrt( (l**2)-( (r**2)*(sin(A)**2) )  )
where r is the radius of the crank, l is the length of the rod, and A is the rotation of the crank, as explained here.
With a crank of radius 1, and a rod of length 4, as illustrated, this reduces to:
sqrt(16-(sin(A)**2))+cos(A)
so this is the sort of expression you can put into a driver for the height of the piston(-pin), where A is the angle through which the crank is rotated.
The rod simply has to be parented to the crank, with its origin on the crank's circumference, and given a Locked Track constraint, making it look at the piston-pin.

If you parent both the piston-pin and the crank to another object, their transforms are evaluated in that object's space, and so the rig can be freely moved around, using their parent. In the example blendfile, it's the Empty called 'Basis'.

this is ALMOST what i need and the math is indeed what i was after however the example you provided is fixed at the world origin and i can not get my head around it enough to jury rig it into my scene. thank you for the reply none the less. it may not "resolve" the problem but its certainly put me on the right track to try and solve myself. i will continue messing with it untill either i work it out or someone here posts another approach (or an addendum to yours). again, thanks for the pointers :)

ok, so i have the tracking, rotation driving and parenting all set but i cant seem to get the equation to behave right. at present the motion itself is correct but the piston pin is moving in the ranges of 2m where as the desired range is 7cm (0.07m). how do i alter the equation to account for an arbitrary diameter "crank"?

im sorry, im not sure i get what you mean? the size of my crank is a diameter 0.07m (r 0.035) and my piston arm is 0.10517 m between the 2 pivots. i edited the equation to what i assume is the r and L variables resulting in this
"sqrt(0.105-(sin(A)**0.035))+cos(A)" but blender just gives a python error in the driver and so i dont know what to do :( i can try and isolate the part and send a blend file over  for you to look at and tell me what im doing wrong if that would help

https://www.dropbox.com/s/0cznil15s83x7x3/Brass.blend3.blend?dl=0 ok, there's a dropbox link to the stripped blend file.

you're under no obligation to, thus making me all the more grateful for the help :)

@AlienXtream   OK, I hope this suits .. In general, I find it's better to construct and test rigs at World 0, an then parent everything to move to the working location. You don't want offsets finding their way into expressions. You could add more variables to the driver, to allow variable crank size, etc.. but that's more for general asset creation, and there's a (small) computational cost.

thankyou SO much, it works exactly as needed. had a quick look but later i will work on implementing it into the original. the scene wasn't something i planned ahead on much and so at the time i had no idea what i was going to need setup. not the best way to go i know but it works for me 99% of the time. again, thankyou SO much for the help

here it is. i felt i should share the final product with you as a small token of gratitude. you basically did the heavy lifting after all, its the least i can do :)
https://imgur.com/a/KI5GUux

@AlienXtream Great! Case closed. And thanks for sharing the result. It's nice to see where stuff goes. Your Q. also got me to fish a very rusty tool from the bottom of my box: the generalisation of Pythagoras which is the cosine rule. So thank you, too.

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


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change particle color on interval
I am learning blender and I would like to simulate a particle system. I have successfully done that with single colored particles. I am not sure how to change the color of the particles in equal interval. For ex, I want the particles to start with red color and after few frames change to green color and then back to red and vice versa for the entire lifetime.
I am not sure of what nodes to play with. Some help is much appreciated.

Per-particle, or all together?

If you want the change to be frame dependent, as opposed to lifetime dependent, I would suggest using a Value node with #frame written as it's input (makes value = current frame at any point), and then using some math to get the correct interval for your needs. Use this as a material for the object you're instancing as a particle.
In the example below, I took the time that the Sine of the frame number is greater than 0.5 (half the time) and used that as a mix factor for a MixRGB with the two colors. This gives particles that alternate between red and green every other frame. You can also use a ColorRamp if you want more control/multiple colors.

Lastly, this works in both Cycles and EEVEE.


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Remove blue screen with blue object on it
I have been trying to learn the basics of Blender and I have a basic understanding of keying. But here is my problem. I only have a blue screen and I am trying to utilize it. The problem is I have blue object which is interfering the keying process. I would like to know if it is really possible to still use the same blue screen and do the keying for the below image.

This is what happens when I try to apply the knowledge I have.

I don't think there is enough contrast anyway. You have the same blue values inside your object. You can try to use the LumaKey, but you'll have to mask out the interior manually.

Keying with a color background that is similar to the objects in the foreground is not a good idea...
Also, the background is not an uniform color, since the fabric has folds and wrinkles, so you will have to key out a large amount of different tones of blue, which will force you to use very aggressive settings for the key, which in turn will result in too much of the image being affected and degraded.
But since you voluntarily put your self on a bind and a challenge, you will have to work extra. KEY the background like you would normally, then you will need to create masks for the blue pail, and use those as core matte.

But you will notice that the key node has also taken away a lot of the blue component from the image, so the output has become useless.
You will then need to use the original image and associate the matte created by the key node and use it directly on the image with a set alpha node and an alpha convert node...

Then you will need additional masks to use as garbage matte to get rid of the dark areas (the folds on the fabric) to have a clean matte.

Then you'll realize that you need to bring back the shadow from the pail on the fabric... Getting the shadow information (and subtle gradations like reflections or transparency) would have been very easy to do with a proper flat background, but now you need to re-invent that portion of the image.
Then you'll realize that one of the other blue objects is also missing, so you need more masks...
This is way too much work for something that should have been very simple (and mostly automatic), extra work that could and should be avoided with proper preparation...

Now that you've seen the extra effort that it takes to do this, change the fabric to a color that is not present on the scene, stretch it so that it has no folds, and make a new picture and key it in a simpler and proper way... Key out that color so that you have a clear edge on the objects, enough information on the shadows and reflections and so on.
Even a black fabric would be easier to key (using a luminance key) than what what you have right now.

Thank you for your detailed answer. I guess its time to get a different color mat and save time.

@susu I'm trying to learn more about the compositor.. I couldn't help noticing that Hue alone made a pretty good discriminator for a core matte, here: (https://imgur.com/a/KMKpIjn).. but struggled to get it to work with single channel or one of the other key options. Do you have any clues how you would get that to work, a 'proper' way, without assembling it by hand, getting decent anti-aliasing, etc? ... Maybe this is another question...

@RobinBetts there are indeed more than one ways to skin this cat. I was just pointing out the core problem. Blue is the noisiest noisiest channel for anything that comes out of a camera, so it only used in cases where green cannot be used, green being the channel with the most information. The keyer node tries to simplify, for novice users, an operation that requires a bit more of a careful approach.

@RobinBetts Ideally you want to make a difference key, with the background using a clean plate, that has all of the pixels that would be missing if the objects were not there. Use inpaint, along with the matte you are creating,  to generate such clean plate, and then a difference keyer should work fine. To have clean or smoother borders you might want to generate some feathering. I'm curious on your answer.


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How to get the exact color as output that we are looking for?
I have been learning Blender recently. And I have understood that lighting plays an important role in getting the exact shade of color that we want. But I am still not clear on how to achieve this.
For ex, I am trying to create a plane for my background with the color(Hex: #ffc1c2). But no matter how much I play with the lighting(Area and point)I am unable to get this color as output in the rendered image using cycles.
Can anyone help me on how to get the color that we want as output.

The values and position of your lights (and world/HDRI) will affect the color of your object, and all the indirect lights as well, so you can't get the exact same color, except, of course, if you use an Emission node.
I've noticed though that if you delete all source of light, create a sun, reset its rotation, give it a Strength of 3.1 and an Angle of 0, you'll get the exact same color in render. So if you want to keep the exact same color you need to stay around these values, or if you play with one of these values you need to compensate with another.
If you test Emission or a sun with this precise setup but still don't get the exact same color, it may have to do with the Render settings (example: the Color Management settings, View Transform must be on Standard).

Thank you. It was the view transform. Playing around with raw and standard did it.

Except this is the worst possible solution for rendering light transport. Your dynamic range is extremely thin, and the mixtures will all skew as the three light mixture cannot be represented in the display output. Don’t do this.

Hello Troy, are you talking about the Standard option?

Using Hex to understand color in blender is not a good place to start. https://blender.stackexchange.com/a/43503/92768 Blender works with a scene referred radiometrically linear reference space mode more info on these links: https://blender.stackexchange.com/questions/35722/when-to-use-srgb-and-when-not-to/35854#35854 and https://blender.stackexchange.com/questions/78284/white-background-with-filmic-blender

and, of course this one: https://blender.stackexchange.com/questions/46825/render-with-a-wider-dynamic-range-in-cycles-to-produce-photorealistic-looking-im/46940#46940


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Is there a way to split a face in cubes (but remaining as one mesh) ? (explode modifier ?)
I want to find a way to split the face of a character in separated cubes (but remaining as the same "face mesh" !), as if my character was a man made from stone for example.
I've tried to Ctrl-B on the desired faces, which gave me what I wanted (I also apply this modification to the arms and hands), but I was not able to scale the new faces inward the character (to create a bump effect), and I don't know if its possible.

Is there a way to do so ?
 - Could the explode modifier help me to reach this result ?
 - Or maybe the Ctrl-B shortcut ?
Thanks a lot guys :)

The frontmost image has used inset, extrude, and some faces between extrusions have been deleted.

Select, Inset, Extrude Individual Faces which can create faces targeted for deletion if you like. Blue sphere shows inset before any extrusion.  Yellow edit mode is the extrusion. Image above.

Inset skipped.  Image Above

In Edit Mode

Face Mode
Make a selection of faces
Inset Faces with the individual option ... See the tools keystrokes listed in the UI. Press I for individual inset [ON]
Menu ... Extrude Individual Faces .  Be careful to use the new selection provided by the tool.  If you loose the selection then use [undo] to recover the selection
Set the pivot for scaling to individual origins .. with the upper tool bar ... yellow arrow
Scale ... to scale the selected faces to the center of each face
Improve these steps

Delete Faces if you like to create islands
Know that you in edit mode you can add another shape such as a cube et cetera
You can always join two different meshes into one mesh

Thanks a lot, usually I don't use this Inset function. In the end that was pretty simple and accurate. Thank you ! :)


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Constraints don't work on curved arrays
I'm trying to do some curved arrays:
I need my duplicates to rotate ONLY horizontally, following the direction of my curve (Image green). I set the twist method of the curve to "Z-Up" which prevents only one rotation axis, but it still rotates backwards and forward on the curve elevations (Image Red). If I use dupliverts, the object does not rotate at all.
I read about "dupliframe" being the solution to it, because you could use constraints to disable some rotations, but dupliframes are no longer available on blender since 2.8 because of programming incompatibilities, and constraints don't seem to work with curve+array duplicates (Image Blue).

AFAIK dupliframe is now instancing: [1]: https://i.sstatic.net/AA73I.png...so your information in the question is not right....


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Mirroring to start Symmetry - object doesnt flip
I'll keep it simple, unlike Max or other programs, Blender isn't flipping the object mirrored. Say for instance I have a 3d shape like this symbol "<" and I mirror it in Max over the center X axis, the result would be this pair of shapes " <    > "
So far in Blender all I can get is this " <    < " which is the same shape, just on the opposite coords of the axis. This is useless for setting up symmetry. How can I properly mirror an object without having to flip it manually?

What process did you use to mirror your geometry ?

Ah, I failed to mention that I was mirroring a Bezier Curve with a Geomery Bevel to Bezier Circle modifier applied to it. Perhaps that has something to do with why it doesn't appear to be behaving normally.
As to how I did my mirror, I moved the 3d cursor and pivot to 0,0,0, > clicked on the Beveled BezierCurve > applied mirror from modifier panel > hit Axis X (then Y for experimental purposes)
Anyway, here's whats going on, I want the shape where the Orange outline is so I can start hair.  https://imgur.com/LlSh9xW

There are a couple of ways to mirror an object in Blender:

Mirror Mofifier

This is an undestructive method to mirror your object with the most control. Go to the object's modifier panel and add a mirror modifier:
(Blender doc: https://docs.blender.org/manual/en/latest/modeling/modifiers/generate/mirror.html)

Edit Mode Mirror

Go into Edit Mode, and press 'CTRL+M' or in the menu go Mesh>Mirror>Desired Axis
This is a destructive but direct solution to mirror your object.
(Blender doc: https://docs.blender.org/manual/en/latest/modeling/meshes/editing/transform/mirror.html#mirror)

Thanks for the reply, however neither method properly places or flips my object, which is a bezier curve with bevel on it. Perhaps my prior post to the person above will clarify in greater detail?

I repeated making a beveled curve and now it mirrors properly.
I think what might have corrupted the other curve is when I tried to edit the positioning of the bezier curve in Object Mode. It appears to move the transform gizmo's location while doing nothing to the curve. Reasons unknown. Thanks anyway for trying to help.

When you use a curve to bevel another curve, the origin position of each object is very important. To avoid any confusion try to have both at the same point in space.


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How to select only the front bunch of objects?
Let's take this for example:

Here each cube is a separate object. And i need to select only the front cubes, like this:

But i don't want to select it one by one. I've tried to select it in orthographic mode by using Select Box

And it selected all of them.
So how can i select only front objects?
I'm using Blender 2.82


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How do you keep simulation bake data in different scenes?
I have a cloth simulation that I want to render in Eevee to achieve a certain NPR look, but also render a shadow on a shadow-catcher in Cycles.
I've done this kind of thing in the past without any simulations, just straight keyframe animation and I do it by copying the scene either linked or not, and then putting the output back together in Compositor.
But when I try to do it with the simulation, the bake data doesn't go into the new copied scene.
I've tried to pin the object from the original scene with no luck, the bake data shows but has no effect on the mesh.
I've tried to convert the simulation to ShapeKeys by exporting as an .mmd and reimporting, but that opened up a whole other can of headaches.
Can baked data be shared over multiple scenes?
Blender 2.82a
OS X 10.13 High Sierra

Have you tried rendering? I had the same problem with parenting, didn't work in VP, looked fine in render. However you don't need scenes for shadow catchers, use Render Layers. If you need more details on that, let me know.

Yes, I have rendered. And again, to achieve the look I want, I have to have separate outputs. I can't switch render engines in render layers and render them at the same time.  I was trying to keep my question simple, but I'm also getting motion blur from another scene as well. All 3 scenes need to have the simulation run exactly the same.

Ups, didn't see Eevee in there, sorry. However, not 100% sure if this is your issue, but Brecht suggests this: https://developer.blender.org/T36382
There's a way to link baked data between files, but tbh I didn't get it to work: https://docs.blender.org/manual/en/latest/physics/baking.html
I tried 2 linked scenes with dynamic hair simulation, with both disk cache and library path enabled, that worked.


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How to keep static mesh in sync with skeletal mesh
I'm brand new to blender and I'm trying to essentially use a static mesh with armor as a second skin for arms, legs, torso etc. of a skeletal mesh. I started with shrinkwrap and while it worked-ish, it conformed exactly like a second skin, which distorted the shape of the armor. Next I tried using a lattice along with the static mesh, thinking that I could then play with the thickness. I couldn't, however, get a lattice that would place the static mesh all around the body segment in question.
I'm hoping someone can give me some guidance on either making the lattice work, or perhaps another way to keep, for example, the static leg mesh with armor, in sync with the skeletal mesh underneath. Thanks for your time.

Some screen of your situation or issue would be helpful. But if I understood ... Parent armor object to a bone should work or parent armor to a three point (vertex) of body as well.

This is a duplicate of many a question on armature deformation, but maybe never quite like this. Anyway, FYI more than one mesh can be controlled by the same armature with an armature deform modifier. Also, vertex groups need not blend across armor parts, I.e. you can deform robot-like parts in a realistic manner without solid bits bending.


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Rotating car steering wheel
Is there any way in blender that if we rotate car tyres left or right, The steering wheel can also move in the same automatically?
Can someone please help me in achieving this.

hello, could you please show your armature? you should be able to dot it with a Copy Rotation constraint

I didn't rigged it till now because of this question that what if we have to do it before rigging.I will use rigacar addon to rig it.

so are you familiar with Copy Rotation? Because I guess it's the solution

Iam not familiar with it but will try it for sure and get back. Thank you for suggestion.

Atlast I figured out how to do it with copy rotation constraint. But the problem is when I join or make parent the steering wheel to the car the rotation messes up. Any ideas?

hello, it's a bit complicated without the object, could you please share a simplified version? https://pasteall.org/blend/

I uploaded the simplified version. https://pasteall.org/blend/c6ffc45b0b7c4cda9f43077ca0e75b62 I used left tyre copy rotation constraint in it. Want to merge steering wheel mesh to car base mesh without messing up.

It looks like the following settings are working: set your Copy Rotation to Mix > After Original ("After Original : The new rotation is added after the existing rotation, as if it was applied to a child of the constraint owner") and Local Space / Local Space (you can leave World Space for the wheel if necessary):

Both wheel and steering wheel are supposed to rotate on their own Z axis here but if the axis were not the same you could have given the steering wheel a Transformation constraint instead of a Copy Rotation constraint.

what do you mean by merge? Just parent wheel and sterring wheel to the car? If you want to merge in one object you need to parent the meshes to bones and use bone constraint

Ok I got this.At first I parented it without keep transform. That is the reason it didn't worked.And
Keeping both as local space doesn't work for me. It works when target is world space. Thanks a lot.


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Sculpting doesn't work. Blender 2.9
so i wanted to try out sculpting with blender. Created a new project (everything is at factory settings) and added a simple cube. Went into sculpt mode but none of the tools seem to do anything and even after 2 hours of trying so many different things, i can't get it to work.
Do you guys have any possible solutions?
The tools just aren't doing anything on any Meshes i'm trying to sculpt.

Have you subdivided them? If you try sculpting a simple cube nothing will happen because there are just 8 vertices for the sculpting tools to try to deform. Select your cube in edit mode, right-click > subdivide and increase the number of cuts to 10 in the popup in the bottom left corner of the screen. Then try again!

Related: https://blender.stackexchange.com/questions/96306/sculpt-tool-not-working, https://blender.stackexchange.com/questions/8200/the-normal-brush-in-sculpt-mode-on-blender-doesnt-work, https://blender.stackexchange.com/questions/105458/no-sculpting-shown-in-sculpt-mode, https://blender.stackexchange.com/questions/124558/in-clipping-border-mode-sculpt-tool-has-no-effect-help-is-much-appreciated

Select your cube, press TAB, then right click on your cube and choose

subdivide.
Then click that little arrow in the left lower corner:

Enter 20 in number of cuts and try to sculpt again.


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When mirroring a object in blender text texture on object get flipped on mirrored object
I have a right leg shoe with texture and want to mirror it on left side like shoe pair...But after mirroring the object the text logo is getting flipped on mirrored object. Any solution to this problem ??
here is the Screenshot of the problem

Of course its flipped, because it is mirrored :D it works the same way you look into the mirror. I guess you have to make a separate texture for that one, once you apply the mirror modifier

Just apply your mirror and mirror your texture.
or...
use this:

check the "Mirror U" or/and "Mirror V" checkbox - depends on your setup.
without "Mirror U":

Its not working for me maybe I am doing it the wrong way
here is the screenshot
https://ibb.co/ZSGJhLb

Please provide your blend file. Looks like you have kind of rotation in it. But your texture isn‘t mirrored anymore. So now let’s face the next problem

Very good you saved me from applying the mirror, thank you, what a small tip can save a ton of time

please click on the checkmark left of my answer if it helped you, thx


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How to get the coordinates of a sliced volume?
I have a project where I need to calculate the immersed volume of a floating body (e.g., ship).
I am starting with the basics, so I am considering a cube for now. The waterline is assumed to be a plane.
In the photo, the cube is cut through by a plane, so Is it possible to get the coordinates of the shape beneath the plane into a python code? and how can it be done?

This will be the immersed volume of the cube in water.

you use a boolean modifier and then you can ask python for the resulting coordinates? And since you hopefully have experience with python you should know how to ask for coordinates...

Bisect at waterline.
Making  the assumption that the water is an infinite plane, defined by location and normal of a plane object, default aligned such that its local Z axis designates "above water".. another option would be to  define the plane, eg  XY plane, and position vessel in relation to it. location (0, 0, 0) normal (0, 0, 1).
Test script.

Water object is named "Plane"

Select context object and run script. The context object is the "vessel"

Using bmesh.from_object loads the evaluated (modified) mesh into a bmesh

Transform the bmesh to put into global coordinates.

Use the global coordinate and global z axis of water object to define our water level

Get the volume of whole vessel,

Bisect with clear outer will leave just that below the water level.

Test script.
import bpy
import bmesh

context = bpy.context

water = bpy.data.objects.get("Plane")
vessel = context.object

bm = bmesh.new()
dg = context.evaluated_depsgraph_get()

bm.from_object(vessel, dg)
bm.transform(vessel.matrix_world)

print(f"Total Volume : {bm.calc_volume()}")
geom = bmesh.ops.bisect_plane(
        bm,
        geom=bm.faces[:] + bm.edges[:] + bm.verts[:],
        plane_no=water.matrix_world.col[2].xyz,
        plane_co=water.matrix_world.translation,
        clear_outer=True, # clear above water
        )
#print(geom) # contains geom of cut
#bm now only has cut and the remaining geometry that is below water level.
print("#Verts")
for v in bm.verts:
    print(f"{v.co[:]}")
print("#Faces")
for f in bm.faces:
    print([v.index for v in f.verts])
#bm.normal_update()
#bm.to_mesh(bpy.data.meshes.new(f"{vessel.data.name} BWL")) # to test mesh result
print(f"Below water : {bm.calc_volume()}")

Result on test cube sliced by default plane.
Total Volume : 7.999999999999999
Below water : 3.9999999999999996

Note, haven't overly tested this. Depending on the volume calculation may need to fill post bisection.

thanks a lot! I will test the code and let you know.

By the way, How is it possible to get the coordinates of the lower part?

Edited to print them to system console.

This script below will print out the upper and lower volumes of the immersed object.
For instance for this object (default cube):

The results are:
5.715525159648066 2.2844748412617073

This is of course in Blender units.
import bpy
import bmesh

immersed_obj = bpy.data.objects['Cube']
water_obj    = bpy.data.objects['Plane']

# add the modifier and change settings

m = immersed_obj.modifiers.get('Boolean')
if m is None:
    m           = immersed_obj.modifiers.new(name = "Boolean", type = 'BOOLEAN')
    m.object    = water_obj

S = bpy.context.scene

# Upper part (assuming water object normals are facing up)
m.operation = "DIFFERENCE"
depsgraph   = bpy.context.evaluated_depsgraph_get()
bm_upper    = bmesh.new()

immersed_obj = immersed_obj.evaluated_get(depsgraph)
bm_upper.from_mesh( immersed_obj.to_mesh(preserve_all_data_layers=True, depsgraph=depsgraph) )

# Lower part (same assumption)
m.operation  = "INTERSECT"
bm_lower     = bmesh.new()
depsgraph    = bpy.context.evaluated_depsgraph_get()
immersed_obj = immersed_obj.evaluated_get(depsgraph)
bm_lower.from_mesh( immersed_obj.to_mesh(preserve_all_data_layers=True, depsgraph=depsgraph) )

upper_vol = bm_upper.calc_volume()
lower_vol = bm_lower.calc_volume()
print( upper_vol, lower_vol )

thanks a lot! I will test the code and let you know.

By the way, How is it possible to get the coordinates of the lower part?

Essentially, you have the bmesh object of the lower part, called bm_lower. You can access its vertices and other mesh elements via the bm_lower.verts / bm.lower.edges / bm_lower.faces collections.


text:
Call an operator from inside a different operator and still show the redo/adjust panel
An artist at my studio requested a custom operator that would essentially be a ‘smart operator’ on a single hotkey that does different things depending on some specific contexts. this is easy to do, obviously- the problem is that when you call an operator in this way the redo panel for that operator doesn’t show up. I was hoping there was an INVOKE flag that would tell Blender that this was the operator call that needed the redo panel but I’m not finding anything.
anybody know of a trick to make this happen, or is this guy SOL? And in case you’re wondering- it’s not as simple as just setting a hotkey for different modes, because the contexts we’re checking for are more specific than that, ie) if edges are selected, do this- if faces are selected, do that.
FYI: cross-posted at blender-artists

kaio got me sorted out. For anyone searching and finding this- you've got to make sure your 'switchboard' operator doesn't have an UNDO/REGISTER bl_option of its own, and when you call the other operator set the undo flag (third operator class option) to True.


text:
Why are my particles behaving weirdly? Resting in odd shape, ignoring passive rigidbody mesh
I try do do an animation where a rock gets grinded into powder. for that purpose i created a particle system that spawns the powder over time. Because i want to rotate the bow later and pour the powder out of it, i made the bowl rigidbody passive and the particles rigidbody active. Besides the particles completly ignoring the mesh shape of the bowl (but not passing through??), they also seem to rest in a cylindric shape. did i miss something? Is there a better way to do this? Thank you so much in advance!


text:
When rendering a 17 minute video, the mp4 is not playing anything
Maybe this is a dumb question, but when I run a test render on the first 100 frames or so everything looks great - renders in HD to H.264 in MPEG-4 with H.264 codec and MP3 audio codec, everything in the sample render looks and sounds like I want it to.  However, when I extend the end frame to the full video length (31,049 frames) the resulting mp4 file won't play anything in VLC media player or Windows Media Player.
I'm not sure why the short render works but the long one doesn't?  The only thing I'm changing between renders is the end frame.
For reference, I'm on Windows 10 using Blender 2.76b.  I'm by no means a power user, but it seems that whether I render using my CPU or my GPU I end up with the same thing - short render gives me a good result, but long render won't play for anything.

If you render at 25% or even lower does it work? The only thing I can think of the is the resulting file size. When you say VLC will not play it, does it open it and what does the Codec information window say regarding the video format, size, width,height, length, bit rate etc?

Thanks for your reply.  I haven't done a lower fidelity render like 25%.  The file size is 914 MB, but the Codec information in VLC isn't showing any details - it's almost like it doesn't recognize the file at all.  Is it possible that I've made it too big for VLC?  I've used it for playing back movies before and I imagine that those would be bigger than my silly little video.
Do you think I ought to reduce the bitrate to make the file smaller or something?

I was looking for the 4Gb limit AVI files have, so its not that. VLC is normally really good at reading video files and giving information even if it does not play correctly. It should not matter but is the .MKV or .MP4 or nothing? I would also recommend using a non MP3 audio codec. MP3 seems like the obvious choice but I think AAC is more common/compatible. Worth trying with no audio to test.

.mp4 is the extension on the final file.  I'll give it another shot with the AAC to see if that changes anything.  Thanks for your time so far.
My other plan is to render in 2 phases - first render into smaller videos that seem to be working fine, then take each of those videos and stitch them together.  Any reason to think that will be more stable?  It'll end up the same length overall but IDK maybe the first round of rendering will simplify things by turning all the strips into one video and one audio...

Blender uses an out of date copy of the FFMpeg library internally and it has some odd issues that have been fixed elsewhere. I often just run the Blender videos through ffmpeg console application just to get a "clean" version. ffmpeg -i yourfile.mkv -c:v libx264 -crf 23 -pix_fmt yuv420p -c:a copy -r 24 newfile.mkv

Not finding a link but always a good idea rendering to images. Then render to vid from the VSE.

The command mentioned by rob helped to fix my .mp4 video
Thanks, rob
I used ffmpeg -i yourfile.mp4 -c:v libx264 -crf 23 -pix_fmt yuv420p -c:a copy -r 24 newfile.mp4
Before running the command you should:

Make sure that you installed ffmpeg
And added the bin folder where ffmpeg.exe is to your PATH
variable if you using Windows

To run the command:

Go to folder with the video and copy its path, for example
(C:\Videos\Blender)
Now press Win+R to open Run menu and type there cmd.exe and pres OK.
It should open a console window
Type there cd (space) and paste the path to folder, for example (cd
"C:\Videos\Blender") and press enter
And finaly paste ffmpeg command I mentioned erlier with your file
names and wait untill it finihed


text:
Mirror modifier Not Working With the Skin Modifier
Whenever I create base meshes to sculpt on with the skin modifier, I add the mirror modifier but it always gives unexplainable results on the back portion of the mesh. I have tried playing with the root vertex but no luck.

delete any faces where the Mirror merges, so there is empty space inside the Mesh and not two connecting faces.

How do you do that when you can only select vertices(Skin modifier)?

If you do not have a base mesh (with faces) then you may need to Apply the Mirror modifier before using the Skin modifier and remove duplicate vertices, this will, obviously break the non-destructive work flow.


text:
How do I make this brighter?
How can I make the water brighter? I have fiddled with lots of different sliders and got nothing. Adding more lamps results in the whole render being too bright(This is my first low poly isometric render and it is incomplete).

if you really can't make it brighter you could use an Emission shader

One of the things that looks to be affecting the apparent brightness of the sea is that the entire scene is bathed in a light of a roughly complementary color, by the World. There's not much blue-green around for the sea to reflect, diffusely. Try changing the dominant light color.. ( it doesn't have to wind up being the color you actually see in the background)

Unfortunately that is a plane, not the world so its not emitting any light. The sea already has a glass shader to create water. I also need to get those two front faces lit up somehow : /


text:
How do you see what vertex groups are assigned to a bone?
I'm working with Rigify and parenting with automatic weights. This is generally quite good, but never perfect and needs some fine tuning. What I would like is to know what vertex groups are assigned to a bone to see if there's any mismatch. Is there any way to select a bone and see what vertex groups are associated with it?
It would be useful to know the other direction too, what vertices are assigned to what group, other than going through every group and pressing select or deselect.

You just need to select the vertex group that has the same name as the bone

The mesh has a collection of Vertex groups that have the same name as the deforming bones in the armature.  To see what vertices are in a given Vertex group, in Edit Mode

switch to vertex select mode to make it easier to see
in the Object Data Properties panel click on the vertex group that has the same name as the bone you are interested in.
click the select button.

To see what Vertex groups a given Vertex is assigned to, in Edit Mode

switch to vertex select mode
select the vertex you are interested in. This only works for single vertices at a time.
In the side panel, select the Item tab.
Under Vertex Weights there will be a list of each Vertex group the vertex is in:

This isn't a rigify example, so "Top" and "Bottom" are the names of bones in my armature.


text:
Blender 2.9 instantly crashes when I try to render in Cycles
Blender 2.9 crashes instantly when I try to either render the viewport in cycles or when I try to render the scene in Cycles.
My computer:
Mac Pro early 2009
OSX 10.13.6 High Sierra
3.33ghz 6-core Intel Xeon
48gb ram
Graphics Card:
Nvidia GeForce GTX Titan
Latest Nvidia drivers
Blender 2.9 doesn't recognize my video card when I pull up preferences. 2.83 works perfectly.

The crash could be caused by an issue in Embree as report in this ticket. This has already been fixed and will likely be included in the 2.90.1 corrective release.

The Nvidia GPU not being recognized in 2.90 is expected, since  Nvidia stopped macOS support for the CUDA Toolkit. The last version that was release for it was 10.12. Therefore, Blender 2.90 does not include support for CUDA. This has been announced in the release notes and is also documented in Blender's manual. Until Cycles is ported to support the Metal API, this means no GPU rendering on macOS.

The same happens to me in 2.91, but it also crashes when I try to import/ append/ link files. Does this happen to you?


text:
How to replace part of a mesh with another part
I would like to make both eyes exactly the same (one is slightly thinner than the other), how would I take the vertices from one and replace them with vertices from the other? The head is a sphere and this is a very dense mesh. Using Blender 2.82 on Mac OSX 10.13.6.

You might need to just manually resize it. Not sure if it's possible to make that kind of change otherwise considering the insane topology.

For a mesh like that, you are using way too many polygons. Retopologizing would help you manage projects like what you want much better. Work with simpler shapes, to get the overall design of your character first, and only then add detail, and you will find that you don't need that dense a mesh.

Was hoping it might be possible to exchange vertex group, similar to exchanging object data.

it could have been possible with Mesh > Symmetrize but your object is not aligned with any axis.


text:
How can I stop IK bones from spinning randomly?
I'm  trying to rig Oleg Ushenok's Mech Spider. I'm using IK bones for the little pistons that are all over the model. I like the 3 part motion that it gives rather than the typical piston setup. The problem is when I parent the first bone in the chain, it causes the whole chain to spin on its Y axis.
The bones in question are activated by raising the gun (the blue curved bone). The movement I'm trying to add is rotating the turret with the gun (The yellow cross bone).
I'll include a link to the blend file, with only a small part of the model that's relevant.
https://www.dropbox.com/s/d0m9lh5qxy9pbzm/Spider%20Robot%20for%20Stack.blend?dl=0

Looking around the file, it doesn't appear that you have set a chain length for any of your IK constraints.  So when you parent them, suddenly everything else, going back to the root, gets involved in the IK.  This is not a situation where I would use IK, so I'm not sure exactly your goal here, but I'd be willing to wager that's at least part of the problem.

I have tried setting it, but it doesn't change the problem. I'm taking advantage of IK stretching to move the bit in the middle kinda independently of the rest of the piston. That's what I'm hoping to preserve. It works better on the 4 on top of the turret that turns with the lower green cross bone.


text:
Shadeless node setup still making shades
I am trying to make a shadeless material in cycles... I tried this setup which i read its supposed to make it shadeless, but still it is has some shades in it, do i need to do something else in order to make it shadeless?
I tried already this setup but it doesnt work.

The option Use Nodes has to be enabled. This can be done in the Shader Editor or in the Material Properties.

I would suggest copying the node group from the Import Images as Planes addon that ships with Blender - import your image and choose the option for Shadeless, and you will see a node group that when expanded looks like this.


text:
i want to create a light that cycles through all colours in the rgb range, how would i do so?
I want to make it cycle through colours to emulate an RGB led light, like a Philips hue, it's for a lamp I'm making which will be in a mockup room.

Select HSL color mode for interpolation.
Choose Clockwise method.
Select pure red color - R: 1, G: 0, B: 0.
Select pure red color and add a bit of blue - R: 1, G: 0, B: 0.01.
Animate Factor - press I over it to put keyframe on selected time frame.


text:
How to add a delay (offset by time) to an objects transform properties that are being driven by another object
Basically I have a Cube and a Sphere. I have copied the transform of the Cube using transform input to a vector math node (set to add to add an offset) and then to the Spheres transform output. Now when I move the Cube the Sphere moves at the exact same time. I want to add a time delay to it so that when I move the Cube, the sphere moves say 10 frames later and always has this delay in moving.
I've seen people doing something similar using instancer setup, but I dont want to create instances, I just want the sphere to move with a delay relative to that of the cube.
How can I set this up?

You can use Action. Here transforms from cube are transferred to sphere with a delay using Delay Action node.

This works perfectly! Thank you. I need to spend a lot more time with nodes :D


text:
How do I put a particular object at the intersection of two faces in a geometry node array?
So I'm trying to create an array of hexagonal rooms which will have a door wherever 2 faces of the hexagon instersect.
How can I go about doing this?
I'm very new to geometry nodes :p
Thanks for any help!

Could you possibly attach a picture that explains the situation a bit more precisely?

hey sorry, i forgot i had posted this question here, hoever all the answers below have given exactly what i needed!

This is a scalable and quite large solution.

Grid
Start by generating a grid that will be laid over the hexagons like this:

Calculate Row Count and Column Count
To generate this grid, we need 3 grid-columns for the first column of hexagons and 2 further grid-columns for every other column of hexagons. Let c be the number of hexagon columns, then we need 2*c + 1 grid columns.
We need 5 grid-rows for the first row of hexagons and 4 further grid-rows for every other row of hexagons. Since every second column of hexagons is shifted by 2 grid-rows, we need 2 further grid-rows, so that we can have the same number of hexagons in the shifted columns.

Calculate Grid Size
The size of the grid will be calculated based on the size of one tile. We expect the tiles to be aligned parallel to the x-axis with two of its edges.

We start with calculating the width and depth of the bounding box of one tile. To get the width of our grid, we need to multiply the width of one tile by the number of columns. We need to multiply the result by 0.75, because every second column is shifted and so we will have the width of one tile plus the length of one edge. The height is computed by multiplying the height of one tile by the number of rows. We have to increase the row number by 0.5 before, because every second column is shifted by half a row.
And here is the complete grid generation:

Grid positions for center of rooms
This means, the center of the hexagons is at positions (1, 2); (1, 6); (1, 10); … and the next column is shifted by 2 in y, so that it continues with (3, 4); (3, 8); (3, 12); … Thus, we can identify grid coordinates with the following rules:
(x-1) modulo 4 = 0 AND (y-2) modulo 4 = 0 and y < (grid-row-count – 1) (x+1) modulo 4 = 0 AND y modulo 4 = 0 AND y > 0
Offset coordinates of the walls
If you take the center of a room, then the offset coordinates for the walls are (0, +2) N; (+1, +1) NE; (+1, -1) SE; (0, -2) S; (-1, -1) SW; (-1, +1) NW
The idea is, to use the ID attribute to mark the different points. The center of every room will be marked with a 4. And when creating a room, we will increase the value of every wall-point by 1. The result will be:
1 = wall
2 = door
4 = floor

Translating index to grid coordinates
The index of a grid is organized in columns. It starts with 0 at the lower left corner, increases with y and continues at the lower end of the next column. Therefore, we need a way to convert between index and grid coordinates. We need the number of grid-rows to do this:
x = floor( index / grid-row-count)
y = index modulo grid-row-count

Let’s create a group node Index -> Grid Coordinates for this task:

By defining the outputs as Integer, they will be rounded down automatically. Thus, we don’t need to add a Math Floor node
Selecting the points related to room centers
Next, we would like to randomly mark points of room centers. Therefore, we need to select all points, that correspond to a room center. How can we do this?
Let’s start by implementing the rules for the grid positions of rooms, that were defined above. Then we can simply put the Index -> Grid Coordinates node in front:

We wrap this in a group node to keep the overview.
Mark room nodes randomly
Now, since we can select room points, we can select randomly from this selection and mark the points as rooms like this:

Marking the walls
Next, we would like to mark every wall of the room by increasing the ID of the corresponding point by 1. But how can we do this? The following steps may seem a little unintuitive. This results from the fact, that you need to think from the end, when using geometry nodes.
For changing the ID of a point, we need the Set ID node. This changes the ID based on a selection. If we use the Index node in the context of this selection, it will be the index of the point that is changed by the Set ID node – in our case the index of the point of the wall.
A point relates to a wall, if the corresponding point of the room center is marked with 4. To read the ID of the room center point, we can use a Transfer Attribute node. But we need the index of the room center point, in order to read its ID.
Starting at the index of a wall, we can calculate the index of the room center point based on the grid vectors, that we defined in Offset coordinates of the walls. We receive the vectors from the walls to the center of a room by multiplying these vectors with -1. Then we need to turn this into a delta index. Therefore, we define a group node Grid Coordinates -> Index:

Using this, we can we define a group node Is Wall, that selects points based on the vectors, that point from the wall to the center of a room:

Input of this node is the vector pointing from the point with the current index. Using the above defined Grid Coordinates -> Index node, we convert this into a delta index and add it to the index of the current point. Then we use this index to read the ID of the target point. We select the current point, if the ID of the target point is equal to our Room Marker, which we defined as 4.
We use this node to mark the walls like this:

We use one instance of the Is Wall node for every wall position and increase the ID of the corresponding points. The walls are split into two groups, so that the opposite walls are not processed together. We do this, because we want the walls, that belong to two rooms, are processed for every room and thus marked with the number 2.
Now every room center point is marked with 4, every wall of a single room is marked with 1 and every wall that touches two rooms is marked with 2.
We can use this, to instantiate the floor and different types of walls.

you're crazy, nice one ;-) +1

I feel so silly. I was constantly wondering how to go about this, but i completely forgot I asked about it in stackoverflow, I just opened the site for the first time in months and here are all the solutions i needed! Bless you!. And thank you for providing me with thorough details. Im learning geo nodes as well so this will be so helpful in understanding how it works!

I have a suggestion...

Essentially, I use this technique here to create a hexagonal grid:How can I create a hexagonal structure with Geometry Nodes?
However, I rotate it by $90°$ and triangulate the mesh, which gives me the following pattern:

I then delete some points from this pattern using the node Random Value (Boolean):

I then instantiate hexagons at these points:

If I then split their edges, I can mark the edges that are crossed by the previously created pattern.
In order to then instantiate either a wall or a wall with a door at these points with the correct rotation, I still need the rotation.
Therefore I convert these edges into curves and subdivide them. The middle point of these curve segments has now the required rotation, at which I can now wonderfully instantiate my walls or whatever.
In this example, I also prepared the elements as curves, which I extrude in this node tree and use as an instance:

(Blender 3.2)

I feel so silly. I was constantly wondering how to go about this, but i completely forgot I asked about it in stackoverflow, I just opened the site for the first time in months and here are all the solutions i needed! Bless you!. And thank you for providing me with thorough details. Im learning geo nodes as well so this will be so helpful in understanding how it works!


text:
How would I make this A into an n-gon?
I just have this "a" mesh, I fixed it up after i turned the text into a mesh, and I don't know how to dissolve these edge loops to make the top and bottom face an ngon since I don't need it to have nice geo. And I can't actually dissolve them, so I'm confused. also I can't just select the entire outside and fill a face because it fills over the hole in the a. Thanks for the help.

Because blender's algorithms can't describe a face with a (unconnected) "hole" in it, edges like this are necessary for areas such as the "hole" in your A - You can move them to have nicer placement, but you cannot remove  them.

You can't make it into a single n-gon, but you can partition it into several n-gons. fill in an edge wherever there are forks in the path - around the center hole, for example. In this case 5 or 6 edges should be enough. Then fill in the n-gon faces. Just beware that n-gons do not deform well. But that's another topic.


text:
How can I make this specific area have the black material?
I can't make an edge loop here, but I want the black strips from both of those sides to carry onto the top on both sides of the model. I don't know how to make that happen and I'm not extremely advanced when it comes to blender. This explanation was probably terrible but hopefully the annotation in the picture can explain better

You could fix it but maybe the best is to start correctly, which means create a circle:

Inset with i:

Join the 2 opposition vertices with J:

Delete the bottom half:

Extrude down:


text:
How would I make a boolean made up of the circled shapes work properly on a small, flat, coin-shaped cylinder

What I'm trying to do it 3D print a small coin like thing and make a slight indent in the shape of the 6 triangles and 4 circled circles into the coin shape. I tried it earlier and it did not work and was terrible, and there's definitely a way to do it I'm just not too advanced at modeling, so help would be appreciated. I can provide more info if needed. (Also not sure how to create the triangle shapes well, I did it but they were bad and interacted horribly with the base cylinder.)

add subdivide the surface and try boolean modifier or upload the blend file and I'll do it for you

Boolean should work, be sure that your triangles and circles are not coplanar (on the same plane) with the base mesh. In other words, make sure they stick out from the base mesh a bit. And try using curves to make the triangles.


text:
Mesh adds color instead of texture
Have a problem where mesh somehow using material in a different way.
I have texture node set up. However the whole mesh is only covered with color instead of it.
Color seems from a texture part.
Have tried to add vertex colors but material shows as expected and the mesh seems to have another color and nothing changes it. s the texture itself is scaled to max somehow.
How to cover the mesh with texture properly?

Adding this material into a cube or other basic mesh results to a good texturing with a proper placement. At least please give some clues on where to look for or what to look for?

Hello :). This typically happens when your mesh doesn't have a UV map.

Press U to unwrap, and maybe choose "cylinder project" for this model?

The default mapping for an image texture is using UV coordinates. If your object has no UV map, then you need to create one by unwrapping the object, or use a different kind of coordinates. You might want to read the following link: https://blender.stackexchange.com/questions/46424/add-a-transparent-image-on-top-of-a-material


text:
How to deal with this coarse mesh for sculping after boolean operation
I forgot to sufficiently refine the mesh on the boolean cylinder to be used on the target geometry. The target geometry now looks like as attached. I tried a general remesh but I lose all my sculpting detail. Are there other tips?
Thanks

You can use the (default) Draw brush, enable Dyntopo (choose the Detail Size you want), put the Strength at 0, and sculpt this part, it won't create any bump but it will triangulate.

Thats a nice tip. I had to use "front faces only"  to ensure only this side is affected. thanks!


text:
boolen operation is not carried over into stl file upon export
I have attached my modelling approach for cutting out a cylinder with another and then exporting it. For some reason, the stl file does not contain the final cut-out, instead it shows the 2 cylinders.
This is the first time this has happened to me. Cannot figure out why. Any ideas?

You need to either delete the second cylinder or select Selection Only in the export function and make sure the first cylinder is selected.  Hiding the second cylinder from the viewport isn't sufficient to keep it from being exprted.

That works!! Thanks


text:
Curve Stroke Option in Draw tool does not appear in edit mode
I am having difficulty replicating the modelling process for the Draw tool in edit mode as shown in this video at 58sec.
https://youtu.be/CjdH1CnX_yw?t=55
I am interested to get access to the "projection depth" and "surface" option so that I can apply my bezel curve to the cube. The draw tool is already selected in edit mode before I select "N".
Am I missing a step? I am using version 2.93.1

Interface has been reorganized a bit. I pretty sure that "Projection depth"  become just "Depth"


text:
When I assign shape keys to text, the objects lose their material
I have created two text objects with the word ORIGIN in two different fonts. I can get the text to morph from one font to the other but after converting the text to curves and applying the shape keys the final text object loses it's material. How do I keep the material I applied to the text previously or do I need to add a new material to the curve object after conversion?
Also the original text before morphing with shape keys is using a mix shader with two emission shaders and texture coordinates linked to an empty to create a gradient wipe effect to change the text from black to white during animation.

Add a screenshot.


text:
Manipulationg images
Only downloaded blender this week for the first time so still working out what its capable of.
One question I cant find the answer to is:
Can you add mesh to a 2D background image in order to make it 3d by moving vertexes in the z?
Many Thanks

Hi. Please make the title of the question specific to what you are asking and not just the general topic. Thanks.

You can import the image as a simple 4-vertex plane with the Import Images as Planes addon.
Then you can add a Subdivision Surface modifier & change the smoothing algorithm from Catmull-Clark to Simple, which will add more vertices but keep the same mesh shape.
Increase the resolution to get as many vertices as you need.


text:
Camera movement slow down in large scenes. any solution
In large scenes, as the camera is zoomed out, the camera movements/panning become so slow that it literally stops. is there any solution beside working in smaller scenes?


text:
Why isn't changing the material of an object visibly working?
First off, I'm putting it out there that I'm pretty new to Blender. The problem is that when I select any object, or faces of a mesh, and attempt to change the material, it doesn't visibly change. A video is linked below so what I'm trying to explain can be seen in further detail.
https://youtu.be/RdlvJl-wcfQ
If you have a solution, please leave it below.
Thanks.

Because you're not in LookDev or Rendered mode (https://docs.blender.org/manual/en/latest/editors/3dview/controls/shading.html).
As a side note, maybe you should start out with a basic tutorial, before you hop into your own projects. It may seem discouraging to actually having to learn something before one can produce results, but so is pretty much every skill that is not trivial.


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Makes edges of frame in animation all blend to uniform color
I was wondering if there is some method in blender to make all the edges of the frames in an animation blend to a singular color so that it can be used on a website with one solid color and blend seamlessly into the website. For example, I have this video here: https://halokeys.com/static/media/elemental75_framed.mp4. The edge frames all have a very similar color but they very slightly especially as the frame changes so it doesn't blend into a solid color website. I have thought about using a transparent background, but the problem is I need to also catch emissions from the keyboard in the video (led lights) which need a surface to project on.
It is easier with single frame renders as I can render the plane on which the keyboard rests as solid black and the reflections of the LED lights don't extend to the border so the border pixels are all black. I then use a python program to replace all black pixels (or near black pixels) to transparent pixels. Since the LED light color is blue, I can then use some math to detect what percentage of 255 blue the pixel is and set the pixel color to 255 blue but decrease the transparency so that it matches the original pixel.
The program looks like so:

img = Image.open('image.png') # replace image with file name
max_b = 255

img = img.convert("RGBA")
datas = img.getdata()

newData = []
for item in datas:
    r = item[0]
    g = item[1]
    b = item[2]

    if b == 0 or (r + g + b) <= 3: # sets inconsistent 1, 1, 1 pixels as transparent
        newData.append((0, 0, 0, 0)) # This is for checking black pixels, replace transparent. Do
        # if item[3] == 0 to check for transparent pixels.
    else:
        transparency = b / max_b
        offset = 1 / transparency # b CANNOT == 0 because you can't divide by 0
        new_r = round(offset * r)
        new_g = round(offset * g)
        transparency = round(transparency * 255) # converts 0-1 to 0-255
        newData.append((new_r, new_g, max_b, transparency))
        print((new_r, new_g, max_b, transparency))

img.putdata(newData)
img.save("img2.png", "PNG")

However, I obviously can't do this for video as it would take way too long so I'm trying to figure out if there is some method in blender so catch emissions with a transparent background or at least have a video with a solid color frame throughout the video so that it works well with my website. Thanks.

Nice render. In my mind, this can be solved through compositing. By using a grayscale image as a mask we can mask out the edges of your render and place it on any colour we like, or leave it transparent if that's more convenient.

To leave it transparent the 'Alpha Over'-node in this setup can be removed from it. If the solution has to be in python I apologize for wasting your time.


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Cycles artifacts?
Anybody have an idea why cycles are creating these artefacts (almost looks like the wireframe is poking through) vs eevee?

Hello, it's hard to guess what is your object and what artefact you are talking about, maybe share your object? https://blend-exchange.com/

The object is a topogprahy I created and the renders are from the landscape. The file is more than a gig so can't really share.  As for the artefacts, see the little squares on the cycles render (top photo)

are you sure that you don't have overlapping faces? Try a M > Merge by Distance in Edit mode?

Thanks, but that's not it unfortunately. I would have expected Eevee to have the same issue but it only happens in cycles.

can you share only this part of your file?

It almost seems in cycles that there is another mesh, hard to explain, please see the blend file  linked. Put the mesh in edit mode and below the hidden faces there is something else which you can't see in eevee, nor can you select it in cycles. http://tinyurl.com/t2muymu6

I can't see any link, please copy paste the link

http://tinyurl.com/t2muymu6  - Thanks for all the help!

I can't see where are these artefacts, I've tried a render in both Eevee and Cycles and it seems ok... Could you please only share the sample you show?

Please see the link for how mine looks in render view when I go into edit mode. I've hidden some faces but there is something underneath in cycles but not in eevee. Are you not seeing the same on your side? http://tinyurl.com/5dd4dh4t

In the last picture you show, could you please highlight the artefacts you're talking about? As I said, I don't see anything, I must miss the problem...

I think I found what it is going on - when I crank up the resolution way high (I'm trying to render for a large print) and renders, the artefacts get  introduced. Still not sure why though. Also seem to be the case when I use a HDRI and not normal lights.

OK that's weird   ;)  ..............

Thanks for all the help though - truly appreciate it.


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Why does blender select an adjacent face when I click on a specific face
When I click the face as indicated in the picture, I it also selects the adjacent face which I don't want.
I appreciate the help and apologies for the entry level question here, still learning.

it seems you have a larger face that overlaps two smaller one (or something like this)? Try to see what you can select when in edge select mode.

yes you should delete this face and refill

I created the faces with looptools, so not sure why it would have this behavior.


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Rendered result is dark
I've applied the picture in the base color as the BDSF but the rendered plane seems a lot darker than the actual reference image (on the left side).  I'm using and HDRI and added a light. Any ideas how I can get the plane (on the right hand side) to be as bright? Appreciate the help

Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.

Plug Image texture directly to Material Output if you dont mind that board would not be affected by lights ... btw if you use Eevee engine - HDRi does not participate in lightning at all (you would have to add Irradiance object) or use Cycles. Or your issue is just Spelucal value that make material reflect envi :)

Maybe replace the principled BSDF to emission shader
and you can increase the strength of the emission


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I am trying to add a custiom property to an add on but it shows me an error
I am following this video
https://youtu.be/XqX5wh4YeRw?t=2451
i have done everything the same way but it does not seem to work
here is my code
import bpy
from math import radians
from bpy.props import *

class MyOperator(bpy.types.Operator):
    """Tooltip"""
    bl_idname = "object.my_operator"
    bl_label = "MyOperator"
    bl_options = {'REGISTER', 'UNDO'}

    #create properties
    noise_scale : bpy.props.FloatProperty(
        name = "Noise Scale",
        discrription = "the Scale of the noise",
        default =1.0,
        min = 0.0,
        max = 2.0
        )

and it shows me this error.
'MyOperator' object has no attribute 'noise_scale'

Quite likely the property fails to register because it has no idea what discrription  is. (Most likely you are alerted to this error when trying to register the operator class) Coding is about attention to detail.  Recommend for blender coding questions here, adding minimal, but runable, code to your question eg the register code for above.

Spelling Error
Quite likely the property fails to register because it has no idea what discrription  is. (Most likely you are alerted to this error when trying to register the operator class) Coding is about attention to detail.  Recommend for blender coding questions here, adding minimal, but runable, code to your question eg the register code for above.
Sure enough, tacking bpy.utils.register_class(MyOperator) to the question code, and checking system console
TypeError: 'discrription' is an invalid keyword argument for FloatProperty()
ValueError: bpy_struct "OBJECT_OT_my_operator" registration error: noise_scale could not register

any attempt to use noise_scale with this operator will lead to error as mentioned in question.
Use description instead and will register as intended.
>>> bpy.ops.object.my_operator(
my_operator()
bpy.ops.object.my_operator(noise_scale=1)
Tooltip


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how to get a mask that only contains the inside of a bowl
I am trying to texture a bowl (procedurally) and I want a part of a texture to only work on the inside walls of the bowl and vise versa I tried using the back facing option in the geometry node but that seems to work in opposite directions of the normals (I think) whereas in this bowl I want the texture to be on the same side of the surface just not on the outside walls of the mesh.
basically, I want the circular white color only on the inside walls and not on the outside.

Is using weight paint a viable option? Is much easier to separate the two surfaces at the mesh level. If you cannot, you can use the normal vector to mask out the pieces: Z pointing up is inside, Z pointing down is the outside. Did you tried that?

Backfacing is nearly there .. it's just that the viewing-point the surface is backfacing to is the currently evaluated incoming ray, (to all important intents and purposes, from the camera)
We just have to create our own viewing-point, somewhere in the object-space of the bowl, and return to what extent the normal of the surface (also in object-space) is front-facing to that.

.. which is done by taking the dot-product of the normal of the surface, and the unit vector from the shading-point to our custom viewing-point. (The viewing-point is the vector we entered in the Vector Math > Subtract node.)

This example assumes the bowl's object-origin is somewhere on its central axis, and the bowl is 'up' in Z. By adjusting the viewing-point, and the threshold angle of acceptance in the Greater Than node, we can get quite fine adjustment: on the left, including the rim of the bowl, in the middle, excluding it.
The pair on the right show how the resulting mask can be used to determine whether or not the color of the surface is modulated by a noise texture.

Thanks exactly what i needed

True normal channel
Given a similar face distribution, you can spot a difference between the normal of the faces on the concave side and the ones on the convex side.

Just sort them with a math node:

And exclude the ones who are pointing straight up if you want to get rid of the border.

Obiuvsly this trick works only for a simple vase like the one you posted, for any other model I would use vertex paint:

True Normal from the Geometry node returns the face-normal, before smoothing, in World space .. so the mask is faceted, and as soon as you rotate your bowl, it will slip?

Yep, sorry, I forgot about the possibililty of this being animated. I'll correct and suggest to use the normal output from texture coordinates node, which "doesn't slip".

Hi, I'm trying to replicate this method inside geometry nodes but somehow the math and compare nodes have diferent outputs to their equivalents in shading. How could this be done in GN?

@JuanManuelLynch I would go for something like this: https://i.sstatic.net/42Zb3.png using the compare node set to "equal", angle 0° and pup up the epsilon till you are satisfied. Let me know if it works for your case.


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Shear along an edge loop maintaining radial geometry?
Does anyone know if there is a way to shear the selected faces using the edge loop at the bottom for each of the faces, maintaining the radial shape of the object as a whole?  The image without the faces selected is the desired affect I wish to achieve, without using booleans.

Shear doesn't seem to work in your case, but you can move your edge, and then easily give some correction on the top face

So there's no tool or operation in blender that can move faces above the bottom ring forwards by varying amounts depending on distance? seems like it's a loss not having a tool like that.


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Simple deform modifier maintaining perfect circles?

I have here a set of faces that are being arrayed, then being deformed with the simply deform modifier to form a circle, the trouble is on the faces I need perfect circles. Is it possible to maintain perfect circles throughout the simple deform operation? I tried using the vertex groups but that doesn't seem to work.

hello, what do you mean exactly? Simple Deform gives you a perfect circle, and this is what it seems to be on your screenshot. Maybe give additional details?

You want the little insets to remain circular?

Robin Betts is correct I want the insets to remain circular.


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Braided cord with curve and bevel curve

I have here a set of two curves with a bevel object that I have made to have limited clipping issues, but the problem comes about when I want to array the two curves, If I try to array them the bevel object does not carry through effectively to the new arrayed curves, and if I convert to mesh and turn the mesh into a curve to bevel the twist of the sections does not carry over either. Anyone know a fix to this problem?

Would a shader solution be acceptable, or do you need the geometry?

https://blender.stackexchange.com/questions/131443/braided-hose-modeling https://blender.stackexchange.com/questions/58959/how-to-model-braided-nylon-sleeve

Edit 2023. Create 2 perpendicular meshes:

Array along X:

Array along Z:

Bend on Z it with a Simple Deform modifier (Bend mode):

Give it thickness etc:

thank you for the response, but as the answer you linked goes, it is faking the detail of braiding, not actually braiding it.

OK I've edited to make it more accurate  ;)


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How to enable all in viewports? Collection manager right hand side
At the right hand side of the Blender UI there is a collection manager that lists all objects, lights, cameras, etc in the scene with their respective collections. Every single object is disabled, how do I re-enable them all at once?

There may be a better way? But here goes..
In the (funnel) 'Filter' dropdown of the outliner, enable the 'Disable Selection' dart-icon, if you haven't already.
If there is a top-level collection, below 'Scene', containing all the others, Shift-click the dart icon next to it, to recursively set the 'Selectable' state of all the collections and objects beneath it.
If there is no top-level collection, you can temporarily or permanently create one.

ShiftA once or twice to collapse the Outliner view and
make it easier to see what you're doing.

Right-click below 'Scene' to create and name a new top-level empty collection.

Select all the top-level collections and objects whose state you want to change, drag them over the new collection and Ctrl-drop them there. This will link everything to the new collection without disturbing the originals.

Shift-click the dart next to the new collection.

Once done, you can X delete the new collection of links, if you want to.
There is also the per-viewport 'View Object Types'setting in the 3D-View header to look out for, if objects are unselectable.

This is definitely a most needed one-click feature ! You can also create a new View Layer, which will toggle every collection on, but there is so many downsides I wouldn't even consider it :)

@Gorgious I think there's a real grammatical problem in this part of the interface. The distinction/equivalence between 'selected' in the outliner and 'selected' in the viewport is not clear. Disabling selection in the viewport should not disable selection in the outliner, for the purposes of changing the 'selectable', or any other property, there.


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Boolean behaves differently depending on file and viewport/f12 render
I have a scene with a Boolean modifier cutting into geometry with difference, when appending both the cutter and base mesh to a different scene the Boolean works as expected. Viewport cycles render displays expected result as well.
counterclockwise starting at the bottom is the other file's cycles render, then the cycles viewport native file render, then cycles f12 render native file.
Does anyone know what the issue could be?

At first glance I'd say, the cutting object is set to be invisible in the 3D viewport, but not for rendering.

if Gordons answer doesn't help, please provide blend file so we can check it out

@GordonBrinkmann Unfortunately not the issue as I the picture from the other file has perfect operation performance. I assume it to be a bug relating to file size.

Are you applying any modifiers before the boolean that results in a different viewport vs. render poly count? e.g. Subsurface

Problem is due to Blender being unstable at render with high polygons. Probably best to wait for a newer 2.9.3 version.


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Constraining axis on rigid body
I've been trying to roll a sphere down a slope and I want to constraint axis of rotation (so that it doesn't veer off course) but adding rigid body constraints (generic) or regular object constraints (lock rotation and lock position) with values to 0 min/max simply doesnt work. The sphere keep going sideways and rotating to values that shouldn't be possible. Am I missing something ? Thanks :)

In the object panel, next to the rotation settings, there are some lock icons you can press to lock those selections.  Try locking everything except the axis you want to rotate around and see if it works

Tried it and it works, thanks ! :)

no problem! :) happy to help


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Cannot edit vertex after join
Also cant edit even though I've been editing in the same object. I needed to redo a torso and separated the arms and head but now that I have brought them back I cannot edit the existing meshes, only the torso I've been working on. Edges and faces are selectable...but will not move, it's like the vertex data is gone.
I've had this happen when I join objects as well, actually never had a successful join with a mesh I couldn't edit anymore, hence the headline. But now I stayed only in edit mode (same object) and the existing mesh is doing the same thing. You can see in the photo how there are no vertex points to even select

I've only had this happen since 2.83 and 2.9 (current). Removing modifiers, applying modifiers same result (obviously I am trying to reapply mirror here), overlay and viewport data unchanged, xray makes no difference, even tried dumb stuff, tried removing dupe verts, duping mesh, etc, nothing gets the mesh back...

I closed and reopened then tried unhiding again because I was running out of ideas. And it worked. No idea why, and can't duplicate it the problem either so I have no explanation.


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"bpy.ops.rigidbody.world_add.poll() failed, context is incorrect" occurs when python script is ran more than once
I am seeing a context incorrect error if I run this script more than once in the same .blend file.  It  occurs in Blender 2.82 and 2.90.  My understanding of how contexts work is only mediocre but I cannot think of a reason why/how the context would change after running the script multiple times.  I also do not know of any context requirements for trying to add a rigid body world.  My end goal is to enable rigid body physics for specific objects and I'm pretty sure enabling rigid world is the first step. I've reduced the code to the following:
import bpy
bpy.ops.rigidbody.world_add()

Reproduction steps:

Open a new general blend file.
Insert code from above, run once.  There will be no error and the rigid body world will be enabled if you look in the "scene tab"
Run the script again, error will say context is incorrect.

Thanks.

When you first start Blender there is no rigid body world added to the context. You can check this by running print(C.scene.rigidbody_world) in the console. This should return None
When you run bpy.ops.rigidbody.world_add() you are adding a new rigid body world to bpy.context.scene If you now enter print(C.scene.rigidbody_world) you should get something like <bpy_struct, RigidBodyWorld at 0x00000225720128B8>
If you immediately run bpy.ops.rigidbody.world_add() again the error you get should be something like RuntimeError: Operator bpy.ops.rigidbody.world_add.poll() failed, context is incorrect This tells us that the operator's poll() method is checking "something" in the context and since we know that what has changed is that we now have a rigidbody_world in our context, we can assume that this is what the poll function is checking for. (actually checking this is a bit of a pain as it means tracking down the operator)
Wrapping up - you have two options.

remove the rigidbody world using bpy.ops.rigidbody.world_remove() before rerunning your script
Check if there is already a rigidbody world added before adding one and skipping if there is.

Thanks, I just added an if for bpy.context.scene.rigidbody_world == None so it doesn't add world if it exists already.  I still don't really understand why adding the world when it already exist would give a context error but at least in the future I will be thinking about stuff like this.

@BkSlayer Yeah context management in Blender is a bit of a pain, largely because the "context is incorrect" error messages usually don't give you enough information and if its a C operator like this one tracking down where the operator is defined and what it is checking for is a pain. In this case its in https://developer.blender.org/diffusion/B/browse/master/source/blender/editors/physics/rigidbody_world.c and is the static bool ED_rigidbody_world_add_poll(bContext *C) method


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Chamfer or bevel an edge with a smoothly varying depth, as if whittled or gouged out
My goal is to create something like a "lark's tongue chamfer" along part of each of 4 edges of a cuboid. This would involve a bevel that has a variable depth that forms a smooth curve, starting at 0 depth, reaching some peak depth at the middle, and then returning to 0 at the other side. The main thing is that I would like to know different ways to control the depth as a curve.
Here's an example, sort of following a circular curve, but other shapes ("smooth", "sphere", "root", etc) would be desirable:

I've created this mesh, but my procedure was long and convoluted, and I'm sure there's a better way someone can suggest.
Additionally, can someone clarify for me: (a) Is there a name for this sort of bevel, chamfer, or shape in general?; (b) Later I want to round off all of the sharp edges (i.e. with a tiny bevel) and I want to (say) subdivide the surface to smooth it out, and for this I understand it might be important to avoid having the triangles shown in my image above, so what should be done about this?
Anyway, below is what I did, including screenshots of key steps. Apologies if the screenshots are not very clear at their default size, but the image itself is available as a larger version. Note that units are in metres...

Image A: Create a 2-metre plane, and go into Edit mode. Subdivide the face 8 times, creating a sheet as a 9x9 grid
Duplicate and move up by a known fixed amount on Z axis (e.g. 0.2m)
Image B: Repeat, duplicating the sheet copy that was made in step 3
Image C: Select the edge loop of the top-most sheet, then hide all but this selection (SHIFT+H). Go to top view, then select the middle-most edge segment of one side
Image D: Turn on Proportional Editing, set to "Sphere" mode. Move the selected edge inwards (i.e. on the X axis only) by 0.1, setting the proportional size to (say) 0.55
Image E: Repeat with the other 3 sides
Image F: Unhide everything with ALT+H. Select everything in the middle sheet now
Image G: Hide everything else with SHIFT+H. Go to top view, then select and delete all interior edges, leaving just the square outline edges. Select the middle edge of each side of the square
Image H: Go to side view and then move these edges again, this time down by -0.1 on Z axis with proportional size still the same as above
Image I: Unhide everything with ALT+H. Select all edges of the top sheet
Image J: Move the top sheet down to superimpose it on the middle sheet (making sure to turn off proportional editing)
Image K: Select the edge loops of the top sheet, and also the edge loops of the middle sheet
Image L: Click RMB and select "Bridge Edge Loops"
Image M: Select the edge loops of the middle sheet, and also of the bottom sheet, and then Bridge Edge Loops there, too
Image N: Select all, and then Mesh => Cleanup => Degenerate dissolve. Fix normals with SHIFT+N. Deselect all, and we're done!

What an amazingly detailed post!
Would something like this work for you?

To save too much adjustment in separate places, starting with 1/8
square tile, open on all the sides you can't see, here...
Assign Edge Bevel weights to the edges shown in shades of blue, all at 1 will do to start with...

Assign 2 Mirror modifiers, one about the Empty rotated  in Z by 45, and another in X,Y,and Z.

Assign a Bevel modifier, by width, limited by Weight, segments about 5, with a profile of about 0.15

Assign a second Bevel modifier, to hold the sharp edges under subdivision,limited by Angle, up around 80 degrees, and a Subdivision Surface modifier.

Tweak the Edge Bevel weights, and other Bevel parameters, to get the scalloped shape you want. If you can't get all the way there, you may have to apply the first Bevel modifier, and tweak that in the geometry, by hand.
Edit: Just noticed your first Bevel should probably have only 1 segment..

Oops, looking a bit harder at your question, the first bevel should have only 1 segment, for flatter scallops.

Great versatile answer, Robin! For other depth profiles, it'd be great to assign or define the edge bevel weights (your 2nd step) in some assisted/procedural way, rather than typing in a "by-eye" or hand-calculated distinct value for each one. I'm thinking like a function, or a ramp value, or one of the in-built falloff methods used by proportional editing. It doesn't look like edge bevel weights support Drivers, so do you know of any alternative way to assign different values in bulk?

@algofoogle Interpolation of edge bevel weights is a tricky issue  ... I can't think of anything off the cuff .. I would be looking at using the percentage setting for bevels, to control with topology, use of the Data Transfer modifier with some kind of template or a script / add-on. For the latter, you would have to decide how you would like to interact with it, and maybe how to give the tool the greatest possible generality, (maybe across other attributes of a mesh, as well?)

Great, thanks Robin :)


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Improve lighting and walls
This is a render (with Cycles) of a building entrance hall.
First, I need a cement walls painted white. How can I do it using only nodes?
For lighting I'm using two point lights on the roof and one emission node inside the elevator. How can I improve de lighting of the scene to achieve photorealism?

Same question was previously closed as "Primarily Opinion Based".  Please don't simply delete and re-ask.  Any edit to the original question will have it considered for re-opening.

For the cement you could overlap 2 (or more) levels of noise, one very thin for the cement texture, and one much bigger for some holes. Also maybe try a bit of glossiness with a Layer Weight as factor. Iit would give something like that:

It can also be more subtle:

Thank you very much for both examples, they are very useful!

welcome to stack exchange! your scene is water tight (i.e close internally without holes)? There are 3 ways to add lighting to your scene:

with the lights objects that blender provides...
with mesh object lights (any object and become it emissive through the materials)...
with hdris, which are 360 deg images with color and with lighting information, that works to simply and with ease light your scene with the colors from the surrounding, you will get more realistic reflections of the background scene and softer/hard reflections, except for the mesh lights and lights that you can color them with any color, get reflections from this objects itself, but not get the same result as the hdri image...

there are some cons and pros of using them, you should use the mesh lights mostly for objects like light bulb, lamps, or any object you want to have light or produce light. For adding plane lights for example you can use either one or another for interior lighting.
For background lighting you should use an hdri, and depending in how is your scene and models structure it can subtly or a lot affect the lighting of your interior, depending if there any holes such as windows (with or without glass on them,curtains or any translucent or transparent object) that lets the light scatter through...
So for your lighting in this scene what is the image reference of the real scene (i guess you made this starting with a reference) you want to achieve and the type of lighting (cool,warm,neutral)? matching the lighting of a real life reference can be tricky sometimes...
Additionally for increase more realism your scene, this current one is too clean the materials, you need to work more in the materials as well, with adding some subtle or a lot of effects like damage,dirt,grunge some bump or normal maps, sometimes displacement depending the type of object to detail, all this done to the materials using pbr textures preferably which you can download online...
But you can use procedural materials, but this is the hardest sometimes and the advanced way, and if you want to make them from scratch will be a waste of time, but at least you can use it in any scene and objects, but since is procedural (it doesn't make magic for different characterization of the textures and accurate detailing sometimes, but you can in manual texturing, or use both is good), sometimes you might need some manual texturing, or using image textures with procedural materials, and like this you can apply them into areas like the floor, walls, ceiling firstly, also other objects surround like metals,wood, glass,plastic, etc...
You can try the node setup from below answer to get some effects on the walls, that's one the easiest node setups to make for this type of subtle details, but also if you care about closeups renders, you might need to add more detail size on your materials/textures for that purpose...

Thank you very much for all the advices!


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How do I TRANSLATE relative to active/cursor?
so, what i wanna do is translate a part relative to an active point/3d cursor while keeping the dimensions of said part constant.
on this pic, the red line highlights the path i want to translate ALONG (line connecting the center of the part i want to translate and the point i want to translate relative to).

i can move a single vertex relative to a point with relative scaling- but it doesn't work with more than one vertex. it scales the part i want to move too.
also, the above pic is just a SIMPLE example of what i want to do. what i want is not a solution to that PARTICULAR problem - but one that applies to everything. thanks :]

You can scale with pivot as cursor, and then put the pivot at median again and scale it back down

yes...that's one way. what i do is put TWO vertices at the center of the part i want to move, relative scale one of those vertices, then select the part with the other vertex as active and snap the whole thing to the scaled vertex. too much work but it preserves the scale PERFECTLY whereas scaling, for instance, by 3 and descaling by 3 doesn't (0.333...). neither is an ideal solution as you won't see the end results while editing - but "it's something." lol thanks!

You are a brilliant

In case like this it could be done with Hook modifer (or maybe even armature). Probably it's not the best solution for what you really want to do as there's no information about that. No way to do that with simple scale

Ideally what you are looking for is a translate using spherical coordinates, which is not currently supported; but it could certainly be added using a small script, see https://blenderartists.org/forum/showthread.php?168749-How-to-set-polar-coordinates&p=1485444&viewfull=1#post1485444
You could make a request, probably in the bug tracker, and see if anyone shows an interest, or if it is worth the effort, learn just enough about Python and Blender's add-on system to do it yourself.

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sculpting is slow on high dpi display
I was about to learn sculpting in blender, and I noticed it's very slow. Just the sculpting. Navigation and everything else is very performant. I tried scaling the blender window so it's 1/4 of my screen, then there's a significant performance increase. It's performant when I split the blender view-port into a little section as well (two view-ports). What should I do? Thanks!

I see many people having issue with viewport performances. try to switch 2.8, 2.81- or 2.79 stable version if that does anything good. For me 2.8 is better to sculpt- but for some its the other way around.

hi! thanks for the suggestion. i tried using 2.81 and 2.79. unfortunately that didn't fix it. i'm sure it has something to do with my display's pixel density (as evident by the increase in performance as i scale the window down). guess it's back to ZBrush for me

Im sure you tried a different video driver. I mostly use Sculptris to do sculpting. Not really happy with how blender deals with high polygons atm ;)


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What are bone matrices?
I tried looking everywhere but everything I've found so far seems to assume that I already know what it is.
Thanks!

I know how you feel, I'm not exactly the best person to explain them, but, in basic 3D game development, the matrix is pretty much the bone itself (typically known as a joint), they're basically used to  transform the vertices of a model through multiplication (dot), and hold all of the location, rotation, and scale transformations.

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What is bone space, armature space, object space, world space, local space?
So, I thought I understood Local space and World space but then I started seeing "Bone space", "Armature space", and "Object space" in tutorials. Now I'm just so confused. How do Bone, Armature, and Object spaces compare to World and Local spaces? I tried searching to no avail.
You don't have to go into detail. I'm sure I'll be able to figure things out in a minimal amount of information.
Thanks! :]

The description of spaces in the constraints section of the blender manual is fairly good: https://docs.blender.org/manual/en/latest/animation/constraints/interface/common.html#space-types
If you are familiar with the concept of local space vs world space, then object/armature/bone spaces are particular local spaces. Object space is the local space for a given object (e.g. mesh, curve, empty etc). Armature space is the object space of an armature, but is especially relevant in pose mode when contrasting with bone space, which is of course the local space for an individual bone.

Imagine each object as its own universe with its own version of where the center is, where up is, where down is, where left/right is, what scale to use, etc and the only way to enter it is to go into TAB/Edit mode.