text:
How to put a unique material on duplicated objects separately?
I've a sphere and then duplicate it. In object tree they are displayed as three siblings. I selected one of them and created a green glass material through node editor however this material was assigned to all three spheres. I confirmed that my selection is only on one sphere. What am I missing?

this also might help understanding how materials are linked to either mesh or object https://blender.stackexchange.com/questions/282475/assign-different-materials-to-different-object-copies

By default, when you duplicate an object in Blender, the copy is a new object but will still share some data with the original (by default this includes materials and textures) and will copy other data, like the mesh (which allows you edit each independently). Because of this, all these objects will share the material the original object has.
To get each object to have its own unique material, you can select them all, go the 3d view header and use Object > Make Single User > Object & Data & Materials + Tex. Or, you can select each sphere, go the material panel and click the number  beside it to make it unique to that sphere.

In 2.81a it has changed to Object > Make Links > Materials

As of Blender 3.6.1, to create unique materials for multiple duplicated objects, select the objects and in the 3D View header menu go to:
Object > Relations > Make Single User > Materials

authors: Илья Дихтяренко


text:
Compositor result won't show
I have problem with compositor.
It doesn't show result in output render until I replug Image into Composite node.
I am rendering 2 layers, but it show only first layer, without anything modified, until I unplug and plug back into Image slot in Composite node. Then it shows correctly.
NODE SETUP:

EDIT:
Result doesn't show in render output. In Viewer it is visible.
EDIT 2:
Here is the blend file. Sorry for wrong file.

We need to see your node setup to be able to help any

I've had similar behavior.  Rendering with F12 seems to work for me as well to 'reboot' the compositor output.  I'm new here so I figure I'm missing something.  Can't wait to see a good answer.

uhhh. I don't understand. the composite never shows until everything is plugged in. It's like saying "this thing doesn't work when it's off". Did I misunderstand?

@Vince Scalia It is plugged in, but doesn't work, until I unplug it and plugit in again or turn off and back on node editor.

@cegaton It is not duplicate. I don't have problem previewing. I have problem getting result in render output (F12).

@cegaton No I don't.

Thank you. I will upload .blend after weekend. I have it in work.

Added blend file

^that file doesn't have a node setup for the compositor

Sorry, I have uploaded wrong file. Link should be correct now.

in the bottom of the render tab there is "Post processing" contains "compositing" option which should be checked

To enable compositing go to Post processing in the Render tab of the Properties Panel and:

check the Compositing option
uncheck the Sequencer option

this will process the render result through the compositing pipeline if the compositing nodes are enabled.

This is an answer for an old version, but in 3.1 both Compositing and Sequencer options still exist, albeit they are now in Output tab instead of Render tab. In 3.1 there is no need to uncheck Sequencer for Compositing to work.

source: Stack Exchange

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

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

sort: votes


text:
Can I print the manual since I can't follow the online tutorials as the type is so small I am 89!
Blender looks like a great program, but the online tutorials even with windows magnification the text is too small to read and at the same time work on a project - with only one monitor available.  I am 89!
The main thing I want is type fonts and I could not find any in the program.  So can I download AND print out the manual? Any suggestions to both the "problems" would be very much appreciated.

I am 59 and have poor eyesight so I can relate. First, try using the keyboard combination crtl and the plus key(+) and minus key(-) to enlarge and shrink the manual or any web page for that matter in order to read the text more easily. This works on the firefox and google chrome browser for sure as I just tested it out. You can also download the manual as a zip file to read it off-line from here https://docs.blender.org/manual/en/dev/. It's still in HTML format so it will open from from your hard drive into your web browser program. I just downloaded the manual myself and it displays just fine in Firefox(my default web browser). If you are using Windows 10 there is also a magnifying glass feature you can use. Google "magnifying text in windows" to learn how to use it. If you really really want to print out the manual you can convert the on-line HTML manual to PDF by using this free service https://www.win2pdf.com/html-to-pdf.html or you can buy the win2pdf program for $35 to convert and print from your down loaded manual. Hope this helps you out.
Regards, Jeff.

Update: Since Blender 2.92 the manual is also available as ePUB, which means that building it yourself is no longer necessary. The download link is on the front page of the manual. You may have to install additional software to open ePUB files though, for instance Adobe Digital Editions or Sumatra PDF.

Unfortunately the .pdf building for the Blender manual with Sphinx and LaTeX is currently a bit fragile. The generation of the table of contents doesn't work properly and there may be formatting issues. The instructions for building the manual yourself can be found in the Contribute  chapter. make pdf is the command to create the .pdf version.
The HTML version for offline use can be downloaded on the front page of the reference manual.

The main thing I want is type fonts and I could not find any in the program.

Creating text objects in Blender is possible through Add > Text.

The font can be selected in the Object Data properties of the text object.

You sir, deserve a medal! :)

I would suggest taking a look at pandoc - you can download the zipped html document and then convert it to epub, (to view on an e-reader), or PDF or any of a number of other formats. (Note that a hard copy printout will consume a lot of paper & toner/ink it might be cheaper to buy a book).

The full manual is 2183 pages long. Therefore, I agree that this will require a lot of paper and ink.

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


text:
How can I position the object origin precisely on a specific axis?
I'm a newbie and again, I'm here with my stupid question as usual.

As you can see here I try to make a door right, and I trying to move the origin point of this door into the middle of the bottom of it. I successfully snap it to the X and Z axis by following some random Youtube video. But my problem is I don't know how to make it into the middle of the Y-axis.

You can directly move the origin point by checking Origins in the Tool tab > Transform.
To snap it precisely to axis, enable Absolute Grid Snap.
Example of moving origin point with and without snapping

Ohhhhhhhhh !!!!!!!! Thank you so much !!!


text:
How do I transfer UVs between high and low poly meshes?
So I created a low-poly object. Then I duplicated it and made it high-poly. Then I UV unwrapped the low poly one. How can I transfer UVs from the low poly to the high poly object? When I try to do it with Ctrl+L, it does not work because of different amount of loops:

It depends on the details of how you "made it high-poly."  If you made it high poly with an unapplied multiresolution or subdivision modifier, ctrl-L will work.  If you made it high poly with those modifiers, but you applied them, then you can make a copy of your unwrapped low-poly, give it those modifiers, and then ctrl-L copy the UV maps from the duplicate to the high poly.
If you made it high poly in some other way, like with dynotopo sculpting, then the short answer is that there isn't a good, braindead way to do it.
One thing you can do is to try a data transfer modifier to copy UV, which is face-corner data.  You would probably want to use nearest corner and best matching normal; you need to hit the "generate data layers" button to generate the UV map layers onto which your LP's UV can be copied.
The problem is that, with dynotopo, your LP may have seams that run directly through the faces of your HP.  There's no right, automatic way to handle this.  You could data transfer, pin most of the verts, and then re-unwrap any bad faces around those pins, which is reasonable.
Another way to handle this is do it on a per-texel basis instead of a per-vertex basis.  You don't end up with a UV map per-se, but you end up with something almost as good.  Start by unwrapping your HP however you see fit (a smart project is probably a good idea), then create a material for your LP that emits UV coordinates.  Now you can bake low-to-high to get per-texel coordinates from your HP.  You can reference this by running your UV into that baked texture and reading the output as a UV vector.

You can select the two objects, and link their UV maps.

Select the "target" object
Select the "source" object (this needs to be the active object)
Ctrl+L> "Transfer UV maps"

doesnt work  that way. They doest not have the same amount of loops

Once you have your low poly textured and ready;

Duplicate the low poly mesh
Add sub division modifier. (This preserves the UVs)
Add shrinkwrap modifier and set the target to high poly model. (To apply all the details)

This way you can transfer all the details like Uvs, textures, poses, etc. to high poly mesh. It's a simple way but always works for me. All the best!


text:
How do I animate an image in the Video Sequence Editor to match the underlying video?
I'm new to the program. In the video editor, is there an easy way to move an added image smoothly in one direction that it will be synchronous with the base video?
I tried splitting the image into many little pieces but it should be easier than that.
EDIT: So I want the picture follow the original movement and stay like a mask.

Could you add some illustration of what you're looking for? (Edit link then use the add image icon

Not sure what you mean by "synchronous with the base video". Also, please make the title specific to what you are asking and not just the general topic. Thanks.

@Bruno If you type "[ edit ]" (without any spaces) it will autoformat it to link to the edit button, like this [edit].

What you want to do is quite easy to do in blender with motion tracking.
Open a new project as VFX File > New > VFX
In the Clip Editor (not the Video Sequence Editor) open the video you want to use.

Add a tracker on the face or whatever feature you want to track.
Track the element.

In the solve tab of the tools window, in the geometry section use "Link empty to track".
And in the scene setup select "Set as Background" so that you can see the image as background on the camera view.
Import the image as plane, set it where you need.
You can then use that empty as parent to any object on the 3d workspace.

To render, composite the rendered image on top of the movie clip (the image used in the 3D viewport is for reference only).

Or you can opt to create 4 trackers and creata a "Plane Track" that can be used to deform an image as if follows the placement of the trackers.
Read:
How would I attach text to a tracked point on video clip
Is it possible to take a mask clip and 'connect' it to a specific point on a moving object?
Overlaying an image to cover a face in a video?

Made my day! Nice to have you back :P

The Video editor in Blender is a very old part. I think it would be easier if you add the image as an object in blender
(add image as plane: see here https://www.youtube.com/watch?v=mc8Ws9Ngjx8 )
and then move the image or move the camera, very nice.
You could even let it drop a shadow and use a background behind it, it would look like you are filming a photograph.
This is a little more complicated than using the video editor, but is also a lot more flexible.
You could for example use the physical engine and kinda "throw" the picture and let it land on the floor and have several images do that, like throwing down photographs.

This can be automated using tracking.


text:
How do I get my offset models to be at 0, 0, 0?
Apologies, I'm relatively new to blender and have inherited this model. I have tried Alt+G and setting the origin points, but the model itself is still off-point.  This means when attempting to rotate, it's axis is about 0, 0, 0 rather than being about the centre of the image.
How do I get the base of the model to sit at 0, 0, 0?

Hello and welcome :). I don't mean to be rude, but what exactly is your question?

Oh god.  Sorry!! I've edited the post.  Basically I want the model itself to sit at the 0 co-ordinates rather than being offset currently - how do I go about doing this?

Switch to 'Edit mode' (Tab key).
Press A key. This will select all the verts in the model.
In Orthographic view (Numbad 5) move the selected group of verts over the orange dot (the origin).
Repeat this step in orthographic view for X, Y and Z.
Back to Object mode, select the model, choose Object> Apply> All Transforms. This just resets any scale or transform issues.

Wow - great instructions - i'll give this a go and feed back, thanks in advance.

Just to let you know this worked great for me! Thank you.

In Sidebar (closed on your screenshot, default 'N' key), at Tool tab > Options > Transform, check Parents:

Then select only Node and Assembly~19063 empties and move it to desired position in supposed center of your object group. Don't forget to uncheck Parents! After that move only Node empty to scene center.


text:
Mesh artifacts only on render
I am making my phone in Blender and my mesh has weird artifacts on rounded corners only on render, not in viewport. Removing doubles and flipping normals doesn't help. I thought it's releated to non-quads on rounded surface but connecting verticles with knife tool also doesn't help.
What is this and how to resolve my problem?

I'm learning myself but try bridging the edge loops on that particular face.. similar to this... http://blender.stackexchange.com/questions/18177/how-fill-face-between-irregular-curves

Thank you for trying to help me but unfortunately bridge looping made artifacts a little bit less visible but that's all.

The mesh is too high-poly to model correctly. You should be using a subsurf modifier to make things detailed (smooth, high-poly) and keeping the topology much simpler.

I got it to look "right" without much work by triangulating those trouble faces, smooth-shading the object, and setting up auto-smooth.
Here is what the topology and render look like (click on it to view it full size in your browser...it's plenty high res):

And here is the blend:

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


text:
Duplicate objects transformation applies to both objects
I'm facing this frustrating "feature" that I can't seem to remedy; when I duplicate an object (and now, even when I create two completely new objects), their transformations/scaling is synchronized. This is extremely annoying when trying to use any sort of transformation keyboard shortcut.
It should be noted by going to the properties menu (N) and manually setting the properties works just fine.
For instance, here is just the camera selected (trust me, I made sure):

And when I try to transform by clicking+dragging on the X axis OR by hitting G->X, this happens:

They are not grouped (verified by going to the Groups list up in the Scene panel) and they do not have parents (verified by going to Object->Relations).
I have tried the unlink command as well, to no avail.
I have seriously run out of options; what did I change to have my G->X shortcuts transform multiple objects? It seems completely at random, too; certain objects seemed to be "linked" to other random objects, and this "linking" is guaranteed when duplicating even when I do a non-linking duplicate (Shift+D).
What gives?

Is there any way you could share the .blend file for this? First guess would be that you've somehow put a copy location constraint on the mesh that's moving with your camera.

Images could be uploaded directly into the question body, it's quite easy. They weren't uploaded and now aren't available

@MrZak I couldn't due to my rep. This was almost 6 years ago. Give me a break.

Thank you for fixing the images @Glorfindel :)

This could be...

Proportional editing, (disable in 3d view header)
Objects can share an action (shared animation data), (check the action space with each object selected)
a constraint, check object constraints
a driver (unlikely this would be setup by accident, but drivers can do this still)

For crying out loud, it was the first one. I read this link to find out I had hit O at some point. THANK YOU.

For debugging cases like this you could try using the following debugging tools

Keep an eye on the View3D Header for information regarding the current modal operator. In your case, you should see proportional editing messages.
In the View3D Properties Panel (N key), under Display Panel check the Relationships option. (in case there are constraints setup like Child-Of, Copy-Transform)


text:
Skin modifiers automated armature loses influence over mesh after applying modifier. What can I do?
( Beginner question )
I first created character using skin modifier. Next I made armature through skin modifier. Next I animated character and everything in posing worked, I saved animation data.
Next I applied skin modifier ( I had to do it in order to texture paint character later ). Armature stayed but it lost influence over mesh completely, my animations stopped working ( Only armature was animated, mesh stayed in place ).
How can I fix this ? Is there an easy way to regain armature influence with the same weights ? Or should I work around this problem by somehow not applying modifier in the end ?
The only thing I care about is to both be able to use skin modifiers simple automated armature, as well as be able to texture paint my character

Have you tried to parent (Ctrl+P, With Automatic Weights) the armature and the mesh?

Chances are you applied the armature modifier by mistake. Recreate one, and set it to “bone envelopes”

Thank You both just as much, both sollutions work ! :*


text:
Animations become messed up after rotating whole object. Is there an absolute (non-relative) posing mode or something?
(Beginner)
I manually create keyframes with an option to include whole bone system of posed character. I wish to render animations of this character from 8 different angles, so I tried rotating it in object mode, but animations become messed when character rotation is different from original. I understand, that when I was posing bones, they must have calculated absolute viewports transform values.
Is there a way to pose armature relative to itself, so I could apply global transform to whole character and not mess up animation ? Or do I have to manipulate only camera to take all angles ?

Bones' poses are relative to themselves (more technically, "the transforms are in local space.")  Rotating your armature should do what you want, with typical use, and if it doesn't, it's due to something that you're not mentioning (no shame in that, you don't know what to mention yet.)  You might consider just re-orienting your camera instead of your armature as a quick workaround for your situation, but otherwise, I would need to see a file to be able to tell you what's going on.

I see. In the end my armature comes from Skin modifier, with bind to bone envelopes option selected, I didn't create armature manually.  Before I selected bone envelopes option applying skin modifier caused this armature to lose influence over mesh.  Could this be it ?

Yes, it could be related.  (Not the skin part, but envelopes, which means an unusual way of interacting with your armature.)  Make sure that your armature is the parent of your mesh object.

Oh right, thanks a lot, I wish there was a way to vote on a comment :)

Generally when you parent the mesh to the armature using Ctrl+P the mesh object becomes child of the armature object (and vertex groups get relations with bones), so keyframing the whole armature in object mode should do what you're looking for.

As @josh sanfelici mentioned in his answer, you can use the armature object in object mode. But this isn't the ideal solution in some cases.
Generally, rigs made correctly for animation have a root bone that allows doing exactly that (sometimes multiple ones for complex parenting animation and offset).
E.G. Rigify has this "arrowed" circle as root:

Using bones dedicated to moving the whole rig instead of the armature object gives you quite a few benefits: avoid having to switch between pose and object modes and storing animation data in two different places, and also offering better support when exporting to other software (some software will not recognize the animations from the armature object + bones at once, or at least not as being the same animation, some will refuse to import a skeleton without root bone to begin with, ...).
Hence, you should definitely use the dedicated bones if you have some. And if you are the one making the rig, you should definitely add one.


text:
What should be first in modifiers order ? Mirror or skin ? How to avoid mirrored skin bugs?
I am constantly confused by this. Every tutorial on Youtube seems to approach this problem differently. Combining Skin with Mirror always provokes endless amount of problems with my mesh - sometimes it becomes doubled and overlapping after applying all, other times it becomes deeply restructured around root vertex, or other times it visually looses symmetry despite mirror. Every time i get back to modelling after a little break I have to face these problems, please clarify it for me

the order depends on your object, I guess most of the time Mirror comes before Skin. Actually you must think as if you applied the modifiers, which one would you apply first to get the proper object, etc

Can You give some examples ? What would be benefit of having mirror after skin ? It bothers me, becasue most of mesh errors happen right after applying mirror

I don't know, maybe sometimes it's necessary, but I guess most of the time Mirror comes before  ;)

please share a file where you meet the problem you're talking about: https://pasteall.org/blend/

I think one advantage of using mirror after skin is that you can use the bisect option along the symmetry axis

https://pasteall.org/blend/6b0546478fe14473bf740e7ea7ad02fb

This is a good example. If You try to apply skin modifier You will notice mesh gets restructured slightly. And I have to apply skin first, as I want to work on base mesh in subdivided mode, apply it, and finally work on details on just mirror mode.


text:
How do I revert mesh to original in Edit mode after finalizing shapekey?
It gets me every time.
I create new shape key, set value to 1.0 in Object mode , go to Edit mode and play with my mesh. Shape key is done and ready, I can see it working when changing shape key value from 0.0 to 1.0 in Object mode. But I have forgotten to rig my mesh and now Edit mode is locked with my last modification from shape key of 1.0. Is there any way to revert my mesh in Edit mode to the state when it is on shape key value 0.0 ? Or is there any way to prevent this situation from happening when making shape keys ?

Edit mode will show you whichever shape key you have selected.  If you want to go back to editing Basis, select Basis in the list.  The values of shapekeys does not affect anything in edit mode; the only thing that matters is which shapekey you have selected.

I had impression, that no matter what shapekey I selected Edit mode was always frozen, but now I tried it again, with moving shapekeys up and down, and Edit mode was refreshed, Thank You !

In object properties you should create two shape keys. Don’t edit the first one. That’s your base. Use the second to create your modified shape. Switch between them by selecting from the shapekey list in the property panel.

First shape key is named Basis by default, I don't edit it, I create another shapekey and edit it. Described issue happened when modifying non-basis shapekey, and when I switch between Basis and this shapekey mesh only changes visually in object mode, but edit mode is still locked in state of shapekey 1.0

Ok, You were right in the end, I must have not been selecting them properly before, thank You


text:
serious extrusion tool problem - why multiple additional vertices are created at one coordinate after cancelling extrusion?
I have had this problem for a long time, most often occuring when extruding something ( faces, armature, vertices ), this time I menaged to capture it in submitted blend file.
The thing is, after cancelling extrusion with right click I experience severe slowdown of CPU that persists for a long time and causes crashes. In submitted example it happened when extruding single vertex with skin modifier. I noticed that every incomplete extrusion causes this vertex to duplicate in exponential way at its coordinate - merging vertices by distance later results in removing from 17 to 170 vertices ! To reproduce this simply extrude vertex from my file, right click to cancel, and clean up mesh merging by distance. It happens despite of auto-merge vertices turned on.
What can be the cause of it ? I suspect there is something wrong with my project setup ? I never encountered similar problem in the internet, yet it happens to me almost every day
Blend file in the comment below. Using 2.92

Canceling the extrusion doesn't delete the new vertices that are created - it only cancels the movement. Some people use this intentionally to cancel the movement so that the pixels stay in place and then scale them down to make an inset (why they don't simply use 'I' to inset a face I never understood).

I read it somewhere, but how come single extrusion cancel of single vertex results in 10-50 new vertices ? Every cancel poses a threat to crash Blender this way. And I was hoping auto-merge vertices would deal with this

By the way, you can edit your question to add the blend file to it, no need to put it in an extra comment.

I guess, if you're selecting vertices (maybe in X-ray mode,) with  some area-selection method, then the number of vertices would grow exponentially., since each extrusion is of the entire last batch. @Gordon.. it's not only insets. there are many other moves that start with a dropped extrude or inset... (at least, for me :) )

@KrzysztofSwierzy Are you sure you only extrude one vertex? Your object has 9, when I merged them all before extruding it resulted in one additional vertex, not 10-50. I've posted an answer below.

@RobinBetts Of course there is use for those things, you're absolutely right... I had tutorials in mind where people want to make insets on rectangulars, they hit E, abort, hit S to scale it, but since it's a rectangular it's not scaling evenly in absolute measures, so they scale it a second time now constraining it to X or Y. This seems very inefficient to me and especially not good in a tutorial where you're trying to teach people something...

@Gordon. Yes. That's barmy. I would knock that 'tutor' off my list, pronto.

I downloaded your file and checked it. First of all, Auto Merge isn't enabled there so it cannot work. The other thing is, your object already consists of 9 vertices, 12 edges and 6 faces all lying in the same spot. Looks like you took a cube, scaled it to 0 without Auto Merge and extruded one vertex and right-clicked it.
I don't know if you select them all before extruding them so that you get so many vertices, I would clean it up beforehand by selecting all with A, then hit M to Merge > By Distance. Now there's only one vertex left. If you extrude this with E and right-click to abort, there are only two vertices now, the original and the extruded one - not multiple new ones.
Auto Merge doesn't delete this new vertex not although you abort the extrusion but because you do it. Auto Merge "decides" after some kind of editing, translating etc. if two vertices are within the Threshold distance. If so, they get merged.
This means, let's say two vertices are 0.05 m away from each other. If you now enable Auto Merge even with a Threshold of 0.1 m, the vertices will not be merged - because none of them is moved or scaled or rotated etc. at this moment.
To merge them, you can hit G and move one or both. If they stay closer than the Threshold of 0.1, confirming the movement with left-click or Return will merge them together. However if you abort the movement, Auto Merge treats them as if nothing has happened and doesn't look if there is something to merge.
The same happens when you extrude a vertex. If you move it just a little within the Threshold distance and confirm the extrusion, the vertices will be merged at their center. But since aborting an extrusion doesn't delete the new vertices and only cancels the movement, Auto Merge treats those vertices as if they were always there so close together and didn't move - so there's no merging.

I see, so thats because of the way I collapsed the cube in setup. Thank You vaery much, I understand how blender handles merging now, I will be able to not crash my CPU after few extrudes now :)

@KrzysztofSwierzy I think it will be the skinning that's gulping down your clock-cycles, trying to work out how to skin the junctions at 512-branch nodes.


text:
Preserve UVs when modifying topology
First question here. I came from a 3DSMax background, since then I've succeeded to find pretty much everything I needed to make the switch from 3DSMax to Blender, except for this : there a very useful option called "preserve UVs" that allows to move vertices / edges /faces without stretching the mapped texture on the mesh. In fact it moves the selection simultaneously in 3D view and UV view.
As far as I know, actually the only way to "Preserve UVs" in Blender is to use the "Slide Edge" tool and select the "Correct UVs" option. I would like to know if there's any workaround to apply this "Correct UVs" option when moving elements in 3D view
Is this a planned feature for the further Blender's updates? Actually it's a kind a straight forward workflow, modeling everything, we have to make sure that everything is ok before Unwrapping UVs. It would be nice to have a way to going back and forth easily.
Thanks for your answers.

I think UV correction added to vertex slide in 2.74 too.

Yeah, thanks. I've tested it. It's a way to do it, but it's not as simple as having this kind of option activated when moving around vertices or edges in the 3D view with the 3D manipulator.
Here we have to use a specific tool to do it.
I guess I'll have to do it this way until this kind of option will be available.
Thanks for your answer anyway.

You can use live UV unwrap and pin vertices on the edges of UV islands or minimize stretch to correct the distortion.

(Late answer). Yeah, this is a good method for complex and organic shapes. I'm actually working on a low poly environment and there's no way to use this.
Here is two examples in Blender and 3DSMax to show how this could be useful, especially when you have to map an environment on a pre-made texture :
Blender
3DSMax

In the following animation I'm double-tapping the g key to move points and edges.

In the video, an entire corner piece was moved and I don't think this can be easily done using Blender yet.  There may be an Addon for this, I'm not sure.
As mentioned in the comments above, the UV Project Modifier can be useful and there is also a way to do something similar in Cycles.
It's called Box Mapping and uses the Texture Coordinates node to create coordinates using various methods, in this case I used the Object Coordinates.  This way, you can edit the mesh all you like without affecting the texture and then once you have the model ready, you can bake the box mapped texture to the UV coordinates.
Here is a quick Cycles render that shows Blended Box Mapping in Action.

This is just a plain cube with no UV coordinates.  There are 3 other cubes that are being used as Boolean Objects on the cube that is being rendered.  The next image shows the node and model setup for the brick box looking thing

You can pretty much do whatever you want to this model and not have to worry about the UV Coordinates.

Finally, the Booleans are applied, the model is unwrapped and the texture is baked.

Now back to the original question.  Loop Cut and Slide Ctrl+r can be set to maintain UV's.  The Inset tool does this as welli.

Or press G three times.
See: https://www.youtube.com/watch?v=aUjbmlgxhXk which shows an example

When moving edges/vertices (with g+g) check "Correct UV" in options shelf

This is not working!


text:
Middle-mouse-button (to move the screen) does not work anymore
It seems my MMB is completely broken in Blender (only in Blender) because not even combinations with this button worked. It worked fine just a week ago, but since i have downloaded 2.76 this problem occurred, even when i switched back to 2.75. I don't know if the download of 2.76 was the impact because i didn't use Blender 2 days before i have updated it.
How can i solve this problem?

Do you mean what happens when you press and hold the MMB?

Ah yes, i mean that. I mistook it, sorry and thanks for the remark.

Seems like your key binding has been changed.  Barring that I suggest a roll back of your machine to a known working date. Then try the install again.

Do you use Photoshop Elements in parallel to Blender? I once ran into such a problem and it is a known issue of PE that the right mouse kind of redirected. For me, it helped to stop PE.


text:
When should I use Quaternion (WXYZ) and how should I handle the W Quaternion Rotation?
From what I've gathered from some comments, it seems that the use of Quaternion or Euler depends on what we want to animate and Quaternion can handle very complex animation and avoid problems that sometimes occur in Euler.
But in which occasions (simple walk/run animation, jump/bounce animation, etc.) is Quaternion commendable, and are there any advantages of using Euler? If yes, which?
I've also tried to understand the usage of the W rotation, but I just can't understand it and therefore am not able to handle it. Let's say, it's recommended to use Quaternion on jump/bounce animations. How should I handle the W rotation? Are there any occasions where I shouldn't change its values via the graphic editor or should I always leave it as it is?

The use of Quaternion rotation is to avoid the gimbal lock problem with the Euler method. Usually if your object only needs to rotate around one axis or two Euler would do the job. Like a wheel or a wobbling top. But when you have to animate a fighter jet that rotate all around your scene you may encounter the gimbal lock. To understand gimbal lock there is a great youtube video here.
https://www.youtube.com/watch?v=zc8b2Jo7mno&ebc=ANyPxKotx5yqp4L-5ns71ub2mroVOiQurhhNglI3Clsz0Ejev6D5cQa628-MDJhSkEYeGL-nj35Kec7Ka1upJrS9ZpoMMMaq_w
There are also gotchas in quaternions, it tends to solve towards the shorter path. Meaning if you were trying to rotate say 270 degree clockwise, quaternions would solve by rotating 90 degree counter clockwise. So to solve this correctly you need to add a in between keyframe to use quaternions properly. As described in this video here.
https://www.youtube.com/watch?v=R7zncPFGYck
DEMYSTIFYING W
WXYZ are interdependent. Therefore we should never modify them in their values entry box individually. To modify the object rotation simply use R and specify the axis you would like to rotate the object in. With that Blender will translate the rotation on screen into quaternions value if quaternions is the selected solving method.
ARMATURE & BONES
When you are working with armature or bones. In edit mode you will firstly be positioning those bones with Euler. When you switch to pose mode and actually animating, Quaternions are used for solving the transformation of your character's limbs. Often in a rig we use IK bones (Inverse Kinematics), and the IK will drive the armature and in turn quarternion will solve the positions of the bone. We will have no need to edit any of the WXYZ values manually.
EXTRA NOTE
Quaternions values are not in degree. Euler uses degree as it's unit. The math behind quaternions are much more complex the 4th dimension (W) allow quaternions method to avoid the gimbal lock of the 3 dimensions that Euler is limited to.

If I understand it correctly, I should never work with the graph editor (change the keyframes), but only with rotating the armature, i.e. the W rotation will be automatically adjusted and I should never change it either. Though, sometimes it might come in a bit inconveniently, e.g. if you want to make an acceleration you would like to give a graph a nice curve. It would be a bit faster to do it with the graph editor. So, do you know if there is a way which will automatically adjust the W Rotation after you've changed something in the graph editor or is the inconvenient way the only proper one?

Like the note says if you need a rotation to happen faster. It must be through some other tools available in blender than adjusting the values directly. Those values are related to one another. If make say a cube on screen and turn it to quaternion solve ... as you rotate the object in the X axis with the rotate tool ... you will find that not only X value changed but the W along with it... hence unless you know how to calculate quarternions by hand and know what you are doing , which is uneccessary .

Bumps in the graphs with quarternions solve are expected they are not Euler and does not behave as a nice curve as Euler are much simpler mathematically. Do not expect them to look like conventional simple math.

To speed up a rotation you can move the keyframes along the timeline to make it happen earlier than later but not change those individual values in WXYZ.

You could also change the interpolation type if you want to. As long as you keep the interpolations of WXYZ in sync with each other, you should be fine. If you're curious to understand quaternions more deeply, beyond the great practical advice this answer gives, this video and the other resources it mentions are great: https://youtu.be/zjMuIxRvygQ


text:
Locking vertices to rotate the object around them
When I create an animation, it's always inconvenient to adjust certain vertices so they don't change their location during an animation e.g. if I want to make an animation about a person throwing an axe to a wall (see picture).
Of course, the bones of the upper- and lower-arm change their rotation since the whole body has to be stopped partly by the arm who's holding the axe. But if I change the rotation of one of these two bones the parented axe also changes its place e.g. it goes into the wall which shouldn't happen.
Therefore, I always have to adjust the bones to avoid this problem. And I have to do it for each frame the tip of the axe is on the wall.
Isn't there a solution to lock the vertices of the tip, so the whole axe doesn't go inside the wall (but can rotate around the locked vertices) even when it's parented to the arm which changes its rotation?

I somewhat understand your problem statement.   I think a carefully chosen few Blender Screen  shots would make your situation clearer.  A suggestion is to search IK (inverse kinematics) and the related FK (forward kinematics) for armatures and see if this help you to express your situation.  A suggestion is to always place an image in the problem statement.   After you determine your images, a suggestion is to rewrite your problem statement.  State what is required and prohibited.

IK helps some bones to stay in a designated location while other bones move in a controlled fashion.  30 minutes of exploring that will help.

I've just added the picture for the pickaxe-scene.

When you use forward kinematics, moving the body will move the arm and hand to follow the body motion.
When you use inverse kinematics (IK) the hand can be positioned and will stay stationary while moving the body. Note that a hand using IK will normally pull away from the location if the length of the arm doesn't reach the location desired.
By animating only clive's body you can see that the hand using IK stays still while the hand using FK moves with the body.

If you enable the rigify addon, you can add a meta rig and generate the final rig to get an armature that has IK/FK controls that you can look at. There are also many rigging tutorials that cover IK controls.


text:
Is there a possibility to move multiple objects to a deferred origin, but maintaining the space between them?
Using "set Geometry to Origin" doesn't do the last thing. I have a landscape and when i do this all the objects are moved to the origin, but e.g. the flowers or trees are in a completely different position (in the terrain).

It should work with multiple objects. Can you upload the .blend file please?

It works just the same as with one object - you select them, and use either Origin to Geometry or to Center of Mass.

I've just tried it with a different file and it suddenly worked. I think there was just something wrong with it (I've edited the question for another one i had (and wanted to ask it a bit later)). But is there a possibility to move these objects to the deferred origin, but maintaining the space between them? Using "set Geometry to Origin" doesn't do the last thing.

Shift+S > Selection to Cursor (Offset) ? (with objects selected and cursor properly placed)

parent them to an empty ( or one of them ) and move the empty

Below are detailed instructions on how to shift multiple objects as if they were one. I am using a house models that is made up of separate models.

Go to Select Menu
Select All by Type
Select Mesh

Press Shift + Ctrl + Alt + C then “Origin to Geometry”

Press Shift + S select “Cursor to center”

Press Shift + S select “Selection to Cursor (offset)”


text:
2D stabilization causes stretching artifacts
In 2.77a, the 2D Stabilize is causing stretched pixel artifacts all along the edges that black.  This problem is particularly strong when animating the Location Influence and Scale Influence.  The artefacts are present in renders, as well as in the Movie Clip Editor with Display Stabilization turned on.

As you can see, on the top edge and left edge, the pixels are stretched to the edges, as if trying to fill the black gap that would be left there.  I had to black out the faces of the actors, as we are still in post.  Furthermore, these artefacts appear no matter what when animating the Location and Scale Influences in the Movie Clip Editor.  Previewing the animated stabilization is impossible, also, because the influences do not update with each frame.  You have to refresh something in the Movie Clip Editor for it to show its true position (like turning 2D Stabilization off and on).
Is this a bug, or am I missing something?
Thanks.


text:
Loop multiple objects along the same path
What I want to do is to have multiple identical cubes all following the same (non-circular) path, each with a different starting offset. And when one cube reaches the end, it teleports back to the start and continues along that path again. I want to do this without having to manually animate everything.
I tried to do what they suggested here: How may I create a continuously looping animation? by animating the evaluation time on the path and making that cyclic, but that doesn't seem to work for multiple objects.
What I want to happen (using multiple paths to do this, want to use a single path):

What happens when I use a single path and set the offset values on the cubes:

It's never easy to help people with "that doesn't seem to work". Please explain exactly what doesn't work, or better upload your blend file.

The animations in your question have text that is excessively small.  Please include screen shots so helpers can read the text.

Using Drivers and Follow Path constraint.
Drive the offset of the constraint from 0 to 1 using Fixed Position.
Hard coded 250 as the path length in frames. The driver method has two parameters, the current frame (scene.frame_current is known to the driver namespace as frame) and the offset at frame 0.
import bpy

path_length = 250 # path length in frames

def offset(frame, start=0):
    # start position at frame 1
    f = round(frame + start * path_length)
    return (f % path_length) / path_length

bpy.app.driver_namespace["offset"] = offset

Sample file and image with Cube (offset 0), Cube.001 (0.2) and Cube.002 (0.4).

Seems to work pretty nicely so far, though I would like to see if there's a solution without the need for any scripting. I'll accept the answer tomorrow if nothing else comes up.


text:
Break apart grid pattern of foams in mantaflow fluid sim
In Blender 2.82, mantaflow was introduced, with a built in way to generate foam, bubbles, and spray.
However, the particles all seem to be a bit too uniform, resulting in a grid like pattern.

Is there a way to distort the pattern?
I am trying to get it to look something like this:
https://www.youtube.com/watch?v=I2EhrzmRQOE
or
https://www.youtube.com/watch?v=vTfGo6tWkzE
Increasing the particle resolution just makes the grid tighter, and reducing the foam instanced sphere size makes the actual foam ridges less prominent (and you can still see the grid).
The sprays and bubbles also have this issue, though to a slightly lesser degree.

It looks like the issue is already tracked: https://developer.blender.org/T73552
Lets hope it gets fixed in the next release. I tried to break it up using a collection and different sizes of ico spheres but that doesn't work really well.

It is a known bug in the official release, it has been fixed in the daily builds.
The first video you linked is actually done by me.


text:
How to loop the particle simulation indefinitely?

I've made a simple snowfall particle simulation (using gandalf3's solution: How to make particles fall like snow). Is there a way to loop the animation, so the transition between last frame and first frame is not visible? Is there a setting to do it?

one way would be to separate each particle and create a loop animation for it (falling from the top to bottom of image) than combine the loops with different offsets, if particles are a lot ,only separate each group on one plane (which don't overlap )

All steps needed :

render a simple animation loop
use the result as a texture for planes
each plane has different UV mapping and image sequence offset

Preparing the texture
first we have to prepare a simple animation loop in this case snow flakes falling from top of the image to the bottom ; for this we use the proposed system by gandalf3 and render the particles only from frame 0 to the frame where all flakes disappear from camera, we will use transparent background for this :
the first setup for preparing the textures :

result image sequence (transparency can't be displayed here )

final setup
create planes and add a material with the following setup :

the image texture is the result of the previous render ,the mapping node is used to create a shift on the X_axis (left right ) while the starting frame on the image sequence texture is used for controlling the Y axis shift (up down )
instance this material for each plane and give it a random values for the shift ,then arrange and resize the planes to fit the camera border from the camera view
second setup for final render

now render this layer for the same number of frames as the last one and you'll get one animation loop as this :

the .blend file

@cegaton nice idea, it could be done with setting the scale to -1 in the mapping node

@Gonzou i have added the file

A more "clean" way to create a loop using particles:
let's say the render range is 300
Create ParticleSystem

Start: -150 End: 150 Life: 300
Remove randomness
Newtonian physics type
object, force etc..

Create ParticleSystem 2 (same object)

new data block based on ParticleSystem (everything same as the first system)
Start: 150 End: 450 Life: 300

Change numbers according to render range and remove a frame from the beginning or end of the range.
Happy Blendering :)
Heres a demo:
https://www.dropbox.com/s/ipp86jqzoeiqn04/SeamlesParticleLoop.blend?dl=1

Thanks for the method. Could you please explain WHY this works? I mean this is just another simulation for another (later) time range. But what in here makes the last frame be the same as the first one? Thanks again.

Using two identical Particle systems will seamlessly continue over to the next particle system that becomes visible. The first particle system is already starting halfway done so the next one that becomes visible should just have to simulate half of the first one. Since the particle systems are identical and no randomness the life of the particles will be the same so born and died in the same place. (You can use the seed if you need to add randomness to the locations)

just a great idea, simple, effective and works like a charm!

Blender as of 2.80 does not include a built-in feature to loop a particle system.  I have conducted some research into this area and although it is possible to custom-craft an external particle system cache that loops, there are several shortcomings in blender's workflow that can either destroy the files, or disobey the data in them.
Start with this "simple" example from http://web.purplefrog.com/~thoth/blender/python-cookbook/particle_loop.html
import struct
import os
import random
from math import *

class BPhysWriter:
    # BPHYS_DATA_* from DNA_object_force.h
    column_words = (1,3,3,4,3,1,3,5)
    column_formats = ("i", "fff", "fff", "ffff", "fff", "f", "fff", "fffff")

    def __init__(self, f, flags):
        f.write(b"BPHYSICS")
        self.f = f
        self.count=0
        flavor=1
        f.write(struct.pack("iii", flavor, self.count, flags))

        self.format = ""
        for i in range(len(BPhysWriter.column_words)):
            if 0 != (flags & (1<<i)):
                self.format += BPhysWriter.column_formats[i]

    def store(self, *elements):
        i=self.count
        f = self.f
        self.count+=1
        f.seek(12)
        f.write(struct.pack("i", self.count))

        f.seek(0,2)
        f.write(struct.pack(self.format, *elements))

# http://blender.stackexchange.com/questions/15577/how-to-extract-convert-data-from-blender-cache-files-bphys-into-a-human-readabl

class CacheRowReader:
    # BPHYS_DATA_* from DNA_object_force.h
    column_words = (1,3,3,4,3,1,3,5)
    column_formats = ("i", "fff", "fff", "ffff", "fff", "f", "fff", "fffff")

    def __init__(self, flavor, count, data_type_flags):
        self.count = count
        self.flavor = flavor
        self.data_type_flags = data_type_flags

        rec_len=0
        unpack_format = ""
        for i in range(len(CacheRowReader.column_words)):
            if 0 != (data_type_flags&(1<<i)):
                rec_len += 4 * CacheRowReader.column_words[i]
                unpack_format += CacheRowReader.column_formats[i]

        self.rec_len = rec_len
        self.unpack_format = unpack_format

    @classmethod
    def parse(cls, f):

        magic = f.read(8)
        if magic != b'BPHYSICS':
            raise Exception("not a blender physics cache")

        flavor = f.read(12)
        (flavor,count,data_type_flags) = struct.unpack("iii", flavor)

        #print( "%d\t%d\t%d"%(flavor,count,data_type_flags))

        return CacheRowReader(flavor, count, data_type_flags)

    def read_row(self, f):
        """
        :param f: a file opened with "rb" (binary) mode
        :return:
        """
        raw = f.read(self.rec_len)

        if raw is None or len(raw)==0:
            return None
        if len(raw) != self.rec_len:
            raise Exception("short read (%d<%d)"%( len(raw), self.rec_len))

        columns = struct.unpack(self.unpack_format, raw)

        rval = dict()
        cursor =0
        # a lot of these clauses are untested.  Feel free to leave me a comment on the stackexchange answer.
        if 0 != (self.data_type_flags&1):
            rval['index'] = columns[cursor]
            cursor +=1
        if 0 != self.data_type_flags&2:
            rval['location'] = columns[cursor:cursor+3]
            rval['smoke_low'] = rval['location']
            cursor +=3
        if 0 != self.data_type_flags&4:
            rval['velocity'] = columns[cursor:cursor+3]
            rval['smoke_high'] = rval['velocity']
            cursor +=3
        if 0 != self.data_type_flags&8:
            rval['dynamicpaint'] = rval['rotation'] = columns[cursor:cursor+4]
            cursor +=4
        if 0 != self.data_type_flags&0x10:
            rval['xconst'] = rval['avelocity'] = columns[cursor:cursor+3]
            cursor +=3
        if 0 != self.data_type_flags&0x20:
            rval['size'] = columns[cursor]
            cursor +=1
        if 0 != self.data_type_flags&0x40:
            rval['times'] = columns[cursor:cursor+3]
            cursor +=3
        if 0 != self.data_type_flags&0x80:
            rval['boids'] = columns[cursor:cursor+5]
            cursor +=5

        return rval

#
#
#

def mission1():
    cache_pattern = "blendcache_particle-loop/synth_%06d_00.bphys"

    create_particle_cache(cache_pattern, 1, 250)

ncols=40
nrows = ncols
particleCount = ncols*nrows

def locationForParticle(pnum, frame):

    u = pnum%ncols
    v = floor(pnum/ncols)
    x = (u/ncols -0.5)*8
    y = (v/nrows -0.5)*8

    r = sqrt(x*x+y*y)
    loopPeriodFrames = 250
    phase1 = 2*pi * frame/loopPeriodFrames
    z = 0.2*cos(r*5+phase1*5)

    return x,y,z

def create_particle_cache(cache_pattern, frame_start, frame_end):

    fpattern = cache_pattern

    with open(fpattern % 0, "wb") as out:
        phys = BPhysWriter(out, 0x40)
        # XXX blender 2.80 does not fully respect this file
        # and will rewrite the particle timings if
        # you use Alt-A to play long enough to reach the end and start a second play cycle.

        life = 9999
        for i in range(particleCount):
            tm = i / (10 * particleCount)
            phys.store(tm, tm + life, life)

    for frame in range(frame_start, frame_end + 1):
        fname = fpattern % frame
        with open(fname, "wb") as out:
            phys = BPhysWriter(out, 3)
            good_count = 0
            for idx in range(particleCount):
                x, y, z = locationForParticle(idx, frame)
                if (frame == frame_start):
                    print(idx, x, y, z)
                phys.store(idx, x, y, z)
            print("wrote %s"%fname)

def set_pad(list, idx, val):
    """list[idx] = val
    even if list is short, we'll pad it with None-s until we can fit the value in the correct slot"""
    while len(list) < idx:
        list.append(None)
    list.insert(idx, val)

#
#
#

mission1()

To use the generated particle system cache you have to adjust the settings to point at it:

The name of the particle system in the list defaults to being blank, but I double-clicked and changed it to synth.  I also checked the External button, and set the File path to the directory where the cache files live.
The first shortcoming in blender's logic is that it does not actually obey the timing information in the *_000000_00.bpys file.  It will look good the first time you play it in the editor, but if you allow the animation to reach the end and loop back to the beginning blender will recalculate all the particle timings according to the settings in the particle system.
And it will discard the timings you created when it comes time to render.
To work around blender's failure to respect the timings the easiest way is to set both the start and end of the particle system to the start frame of the particle simulation, and generate your particle cache with all particles matching that frame, and the same lifetime that you use in the particle cache.  Since this does not accommodate particles that are born or die during the animation you will have to compensate by locating those particles off-camera for frames when you want them to be "dead".

If you do not do this before you rig the external cache you will discover another defect in blender.  It wipes your cache during the steps necessary to re-enable the panel containing the Emission settings

uncheck External
uncheck Disk Cache
click Free Bake button

and now the files you have constructed have been deleted by blender and you must regenerate them.
The code above generates the looping particle cache using a (relatively) simple formula for particle coordinates.  It is also possible to create the looping particle cache by copying data from a particle cache generated by blender's built-in capabilities, but I haven't cleaned up that example to a state where I can publish it.


text:
How to map the displacement texture?
I've added the Displacement Modifier to my object with a Wood texture for displace. How to change its location, rotation and scale (like you can do with image textures: Map a procedural texture like an image texture)? There are no mapping options in the Displace texture panels. I'd like to rotate the pattern pictured below, so it's mapped verticaly. How to achieve this?

The easiest way to do this is with an empty (empties can be thought of as an object that only stores loc, rot, and scale).
In the modifier, just switch the type to object, and then specify an empty in the drop-down box.

Here is an example blend:

Thank you. I still wonder why I haven't found it by myself :). This is what I need.

If I got what you asked, you can do something (little) mapping the displacement as UV, then unwrapping the displaced mesh, and setting the mesh UV as modifier target. Then (eg) rotating the UV, the displacement rotates. Scaling the UV, the displacement scales.
eg:

then rotating the UV:

while to scale it on the mesh (horizontally, on the displaced surface, here a simple plane):

To scale it vertically, of course you just need to set the modifier's "strength".
Of course you can also see the edits in realtime, setting the modifier to adjust the edit cage to the modifier result:

In that case it could be faster to set the modifier's settings to Object and point it to that plane as well.

Uh, yes, also to an empty, eg. True :) but using an object you get the object mode transforms, while using the UV you can also play with part of the UV vertices, and get interesting (ie: weird) results on the modifier... but that's just a secondary effect...

Thanks man! Cool solution though I wanted to apply it to sphere, so pycoder's solution is better in my case.

Good! Of course using a simple object is better, but when I tried the UV option, I started wondering which possibilities could give to adapt, through the UV mesh, the displacement deformation to specific parts of your mesh... someday I'll have to play with this... but I also guess the UV grid can't be animated on its own...

@m.ardito I see many possibilities to use your method in future. BTW I guess UV grid can be animated via AnimAll add-on.

authors: Богдан Мельник


text:
How to control the position of an IK bone using another object
I have a character who needs to open a cupboard. The simplest way to do that seems to be to add a ChildOf constraint to his hand controller, link it to an Empty which is parented to the cupboard and positioned at the same place as the doorknob, and then animate the door's rotation..... except that when I do this, the whole rig moves. (It's quite funny, but not what I want.) How do I have the empty affect only the position of the hand controller?

Doh. I was using an object constraint (which was causing the whole object - ie, the rig - to move) rather than a (second) bone constraint. Which I needed because it's, you know, a bone.
As you were...

Well, glad you found out by yourself!  Don't forget to key down your bone's transforms before and after keying down the ChildOF constraint influence, it might save you from some headaches down the line.


text:
Interactive motion paths in Blender - do they exist?
In After Effects, you can affect the curve of a motion path without inserting any extra keys:

Linear, straight motion path

Same keys, same speed - but now the null will follow a curve
I know Blender has a "calculate motion paths" option where you can see what the motion paths will be, but it seems to have two huge disadvantages: first, you have to manually calculate it each time, and second, you can't drag vertices or handles around to interactively change the interpolation between keys. Also, it's slooooow.
Is there a way to get AE-style, interactive motion paths in Blender somehow? It's a real pain trying to either guess what a curved path will look like in 3d space from the x, y and z paths in the curve editor, or inserting a ton of extra keys I don't need.

https://blender.stackexchange.com/questions/52830/is-it-possible-to-create-a-path-from-an-existing-object-animation/

Oh great, hadn't seen that - thank you!


text:
Camera tracking problem - focal length seems wrong
I've tracked some footage with a view to replacing the background from the bottom of the fence panels up (this is a test shot for now). I shot the footage on a phone (13mm focal length) which Blender has extrapolated as 17.16mm. The solved camera seems off, though. I've made a line of dots going along the Y axis to test the perspective - I don't have an accurate floorplane, so have had to rotate these manually to match the camera - but you can see that even with Blender thinking the lens is longer than it is, it still doesn't look long enough:

To my eyes, there's too much parallax here. The track looked fine to me (average solve error 0.27px, and the dot that's selected in the screenshots doesn't slide around at all) but I'm obviously doing something wrong... any ideas?

Under Movie Clip Editor properties (N) > Track tab > Camera ... you can specify your camera specification directly. For more probably share your test footage and your simplified blend file.

probably related too https://blender.stackexchange.com/a/16225/2214


text:
I want to be able to distribute instances which are snapped to a triangular grid within a volume
I need to fit a load of hexagonal objects together within a volume. I have them snapped to a triangular grid using two mesh lines, one of which has every other vertex displaced 0.866 in Y. I've then generated the volume I want this to fit within, which is also a hexagonal shape. This will appear based on a map (currently a musgrave texture), like this:
https://vimeo.com/825833092/1f45105408?share=copy
How do I cull the point cloud I've got (shown here with hexagonal proxy objects) so only the points within the volume above are included?

OK, I worked it out. I didn't need it to be a volume - using the Raycast node with the hexagonal mesh as a target, then feeding the Is Hit output through a boolean Not node to Delete Geometry, this gives a point cloud which only contains those points which are above the large hexes (in this case).


text:
Is there a way to output a mesh from an arbitrary list of meshes in geometry nodes?
This question shows how you can build a node tree to select between mesh 1, 2 or 3, but it's pretty manual. Is there some way to do this for an arbitrary number of meshes, so you can add extra meshes without having to build extra node branches?

Collection Info node

Brilliant - that's exactly what I needed. Thanks!

The credit for this answer actually belongs to @MarkusvonBroady as he mentioned it in the comments, and it seemed to be what was asked for. But for all people who cannot figure it out with the hint at Collection Info node, I thought I'll give a longer explanation.
First of all, here is a possible nodetree:

With the Collection Info (make sure Separate Children is enabled to work correctly) you can use a Separate Geometry node set to Instance to pick the object which Index is equal to the value you choose.
In the example I connected the one integer input of the Math > Compare > Equal node to the Group Input to be able to select the object in the modifier. Then I have a collection called "objects" which contains the objects I want to choose from. Each object gets an index from 0 to $n$ - 1 for $n$ objects in the collection. The comfortable thing is, every object you put in this collection can then be chosen without the need to change the nodetree.
One important thing to note though: objects put in a collection will be sorted alphabetically, and therefore re-sorted whenever this alphabetical order changes. And then the index numbers will be re-arranged, too - they will always go from 0 for the top object to $n$ - 1 for the bottom object. An object does not keep its index if it is sorted into a different position in the list.
Which means, if you chose object 3 to display and suddenly you add a new object that gets placed above it in the list, index 3 would no longer select the object you originally chose and you would now have to switch to index 4.
By the way, it is possible that after adding a new object to the collection, the selection still shows the object you originally chose although the order has changed. This is temporarily because the nodetree might not have been refreshed. As soon as it is by maybe switching the index number etc., the new order of elements is established.
If this is not relevant, you can simply add or remove objects to the collection as you wish. If you want to make sure that existing objects keep their position in the list, you might want to think about naming conventions like placing a number in front of an object's name so they are sorted by these numbers.

+1 but why deleting? Just pick...

@lemon Oh yeah, you're right... when I built that my mind was influenced by the other answer... better with picking, I'll change that.

Not sure why I don't have the select geometry node you have, but his should work.

It simply gets the number of instances in a collection and destroys all but one selected by random

You don't have the Select Geometry node because it is a custom nodegroup. The question to which @Nickh129 links to at the beginning is showing a node setup which you can arrange to create a custom group like that. By the way I don't think he was asking for selecting random meshes, just being able to add or delete objects to choose from without the need to adjust the nodetree.

Nobody has that node - I hacked the screenshot together in photoshop. But the Collection Info node is a much more elegant way of doing it anyway.


text:
Why would a simulation nodes setup stop simulating after a certain length of time?
I've got a fluid sim running in simulation nodes (based on Bad Normals' setup). I need it to work for quite a long time (around 5000 frames), but I've noticed it currently stops moving the particles at frame 1567. This is just the simulation nodes part of the geonodes setup - there are other nodes making the particles spin, and they keep spinning past this point.
The frame range currently runs from 1 to 3215. There's no simulation range set in Scene > Simulation. It feels like I'm missing something obvious :S
(Blender 4.0.2, RTX 4090, 128GB RAM)

Did you try baking your simulation zone ? Otherwise, I think your cache may be full.

I've baked it, yes - does the cache have a maximum size though?

I'm not sure. You'll greatly increasing your chances of getting useful answers by uploading your file with https://blend-exchange.com/ and adding some screenshots to your post.

@Nickh129: as Lutzi commented, and to say it more directly: how shall we help you without seeing any of your technical settings you made?

Fair questions, and thanks for your help. I can't really share the blend file as it's a project for someone else, but I think this is probably a weird cache issue. I'll try deleting and remaking the cache and see if that fixes things - just wanted to see if there was something obvious I was doing wrong

@Nickh129 Consider deleting all privacy-sensitive content (objects, textures, images, ...) and upload it. Be careful though.


text:
Trying to make a spring simulation in simulation nodes
I've got a 2d fluid simulation in geometry nodes (which works). I want to displace in Z depending on the luminance of a texture (which also works), but the particles jiggle about too much, which I don't want. So I had the idea to dampen the motion by rigging up a spring simulation which stores the z component of each particle, then moves them each frame based on how far away they are from where they should be.
But I can't get this bit to work. I'm storing z-pos as a custom attribute, but I can't work out how to reference this in the right way so it's looking at the value from the last frame. Oh, and the node setup I've put in for this bit doesn't work either.
Here's the bit that works:

The node graph with nodes expanded:

And the result if i connect it...

The (2d) simulation itself is cached. But it doesn't matter if I roll back to frame 1 and play from there, I still get nothing.
FWIW the geometry is generated by the fluid sim itself, circled in red.

What am I doing wrong?


text:
Is it possible to continue baking a cache from the last .blob file, after a crash?
I've got a simulation nodes particle setup which is around 2000 frames long. Blender won't bake it at the particle density I need - it keeps crashing after a few hundred frames, and the only way I can get it to cache end-to-end is by dropping the particle density a lot more than I want (I need it around 5000, and the most I've managed to cache all the way is 1250).
Trying to bake it with a pre-existing cache via the Physics tab doesn't do anything - the playhead skips through the frame range really quickly, as the node setup is deactivated. Using the Bake node seems to just delete the cache and start from the beginning again. Is there any way to force Blender to pick up from where it left off? I'm only guessing, but wouldn't the .blob files contain velocity and other custom attribute information per particle, rather than just position data?
Using Blender 4.1.0, 128GB RAM, 24C Threadripper 3960X.


text:
Logarithmic curve with spiralling cross-section
I'm trying to make a logarithmic curve with a rotating cross-section.
I have created a curve object following the instructions at
How to create this kind of spiral tube?, giving me the curve shown below, which has an elliptical cross-section that increases in size along the length of the curve.
However, as well as the size of the ellipse increasing along the curve, I would like it to twist, giving a 'corkscrewing' final result that will superficially resemble fusilli pasta.
It seems like this should be a simple thing to do, but I can't see a way to do it.  Can anybody help?

(source: dur.ac.uk)

Have you tried the tilt property of the curve's control points?
If you select one or more curve vertex and press Ctrl + T you enter tilt editing mode where you can control the twisting effect of the curve.
Depending on how your curve was built you can control this for one or more vertex at a time.
If you need to make a smooth gradient across a multitude of points you can use Proportional editing O key to affect adjacent vertex. Use Mouse wheel  to adjust the affected radius.

Brilliant – that's just the job.  Thank you.


text:
Exporting interactive Flash content
Does anyone know if it its possible to export an interactive interface with an image with Blender for Flash? I'm sure its possible but think I may be missing a few plugins. Thanks!

" I'm sure its possible " you say, but based on what evidence? You can render raster animations , if that's what you mean.. but authoring .fla or .swf interactive files is not something that i've seen Blender plugins for. Flash is almost on its last legs, what do you need it for? Web-based interactive interfaces?

Thanks for your response and I appreciate your help! I am indeed hoping to create a web-based interactive feature/ interface which responds to simple user commands pan, grip, zoom etc. I have been experimenting with Blender for this application over the last three months but have been unable to figure out if it can export such a feature for online purposes. Flash has hosted such content in the past but I would prefer to stay away from this avenue if possible. Any advice?

I don't believe it to be possible. You can render out flash video, but not interactive stuff. However, if your aim is to have the flash content in a webpage, you could look into Blend4web. Instead of a webpage with Flash, you get a BGE game as HTML5. This also theoretically works on mobile devices (though often low fps)

Try exporting using three.js

the Blend4Web is the way to go, even NASA used it:  https://www.blend4web.com/en/article/139/

Sorry for the delay. I have had a look at Blend4Web and it sounds like it is perfectly capable of programming out the interactive, visual interface that I have been striving to develop! Thanks for your advice everyone, I appreciate all of your help and expertise!

It is possible to export a raster animation for Flash, (.flv). There are no Blender plugins (or native features) that let you author .fla or .swf interactive content. Some parts of the flash format remain closed source, but if someone really wanted they could using the MXMLC compiler.
The grasp that Flash once had on the interactive web has faded significantly with the growing improvements in JavaScript and adjacent technologies. Egged on a little by Apple's decision to stop supporting Flash directly on it's mobile devices. In light of recent (July 2015) revelations about years-old, but profound, security issues, the public's sense of trust in Flash isn't improving.
There are solutions for getting Blender content online and animated + interactive:

Code WebGL directly
Three.js
Blend4Web

intended to make the process a lot easier, a shining endorsement is the fact that NASA uses it. See this other answer about interactive web tech built with a direct pipeline from Blender.
Why the blender browser plugin is not updated?


text:
Non-operator equivalent to bpy.ops.uv.smart_project() available?
I am using a script that is heavily relying upon bpy.ops.uv.smart_project(). I got the impression that the function has a big impact on performance, so I was wondering if there was an equivalent that is no operator (which might be faster in turn as it does not have anything to do with the UI).

As far as I know, operators called from scripts don't invoke the UI at all (unless you explicitly make the few that support this to do it). So if you feel that you have performance issues with this operator, it's probably simply because it performs heavy calculations. You might want to try find another way to achieve the same goals with less resource intensive methods.


text:
Why can't I see my object when I start the game engine?
I started using Blender a few days ago but I've got stuck with the camera.
I'm trying to make a simple maze game with a moving cube as character, using some tutorials and this is the result.

The selected camera you see is one I added by hand: I deleted the default one and added this with Shift+A > add camera > etc...
The problem is it doesn't render anything when I press P.

I've tried making the camera active by clicking Ctrl+0 and It seems to be active indeed, but I still get nothing at all!

First of all I suggest to switch on texture mode(the little menu right of "object mode"). Then ensure you see something through the camera in Blender 3D window. Newly added cameras are often placed at the scene origin (0,0,0) with nothing to see.

I really don't understand. If I take the default project, then delete the camera and add it again, it wors. Here I've only added a plane, subdivided it, selected the tiles which would be the walls and then pressed "e" and "5".
If i follow your indication I get something in "texture mode"... and it still doesn't render, and I can assure you the camera is not in 0,0,0 ahahah

No the texture mode is not the cause ;). It was just a hint. There can be a few reasons why you can't see anything. To investigate further I suggest to add a cube in front of the camera and see if that is visible. This way we can tell it the camera sees anything.

Make sure it's not invisible in physics.
Make sure the normals are facing the correct direction.

Your answer is being flagged as low-quality. Perhaps you could consider adding some more detail, such as an image or additional instructions illustrating how to do these things.


text:
Are there any disadvantages to starting blender with the --enable-new-depsgraph argument?
The question says it all :). I'm asking because it solved the latency problem between parents and children in the viewport and I will use this as the default blender starting argument (blender --enable-new-depsgraph).

You can watch and track any Dependency graph bugs here:
developer.blender.org > Dependency graph
All of the tickets look resolved now. There are no disadvantages that I know of.
However you never know if somewhere is a bug or not before you test it. If you work in a production environment you probably already test everything before you use it. If your tests are fine I would use --enable-new-depsgraph with ease in mind.

The new dependency graph was introduced in 2.75, so it's had some time to get its bugs worked out by those who use it. I'd go with it if it's fixing a latency issue. "If it ain't broke, don't fix it" or in this case, "if it's fixed, don't break it."  :)


text:
Why is Blender not letting me move an object that has been keyframed?
How do I stop Blender from forcing an existing keyframe position while I'm trying to move the object/bone to set a new keyframe? This seeming position/screen refresh is slowing me down. (Note: "Snap to..." is not enabled.)
The steps I'm doing to set a keyframe:

I Select the object/bone with Right click and then set a LocRot or LocRotScale key using "I" on the keyboard.
I move along the timeline and Select another object with right click.
I re-select the 1st object/bone via right click
I press the "R" key on the keyboard to rotate the object to a new position. But the Object/bone refuses to rotate. It WILL rotate toward my mouse but flitters back and forth between it's keyed position and the new position. As soon as I release my mouse the object/bone "snaps" back to the keyed position.

As long as I don't have a keyframe on an object I can move/rotate it wherever I want. However, once I set a keyframe I can't re-position said object/bone in the 3D-Viewport (using the mouse OR the sliders). I'm forced to set a new keyframe before re-positioning, and to change the keyframes in the Graph Editor one channel at a time. This is hardly time saving or an organic workflow for animation.
I've had this problem with Blender 2.78, 2.79, and now even after buying a new computer in 2.81. I've shut down the program and re-started the project in 2.82.
Here is The current Blend File I'm having an issue with:

The culprit at the moment is the empty named "_CameraPivot."
The "force keyfrsme refresh", or whatever it really is, is not happening at the moment but I anticipate it will happen again. Even restarting the program and re-opening project in 2.81, even after saving the project in said state, results in the "force keyframe refresh" being gone. But I can't constantly be shutting down my workflow and restarting the program every time this problem raises it's ugly head.
I can't help but think there is some hidden command key for this as a function which I'm not aware I'm pressing (I.E.: Like how pressing the Caps-lock key, toggling/hiding the brush cursor, in Adobe Photoshop is an annoying/panicky thing if you don't know the function exists but a useful tool if you do.).
Is there anyone who can help me with this issue/function? It's got to be a simple thing as it's not covered anywhere I can find.
Here's a video link to the problem I'm having: RecordedVideo

Hi. I suggest you lay out the exact steps you are doing, e.g. "1. Select an object with left click. 2. Press [keyboard key]. 3. etc.." so we can diagnose the problem because, at the minute, I have a hard time understanding what you mean regarding "The Refresh" and " and "As long as I don't have a key on an object keyed". Thanks.

The object/bone behaves as if I'm trying to move/rotate it while playing a keyed animation. Which is not the case.

Hi. If you have more information to add, please add this to your question by using the [edit] link. Comments aren't really for extended discussion. Thanks.

Okay all of that is corrected now, Ray Mairlot. Can someone still help me?

As I said, additional information in the comments should have been added to the question. I have done this now.

This is a very odd issue which seems to be caused by the 'Import Images as Planes' add-on. Disable the add-on in the Preferences (and re-enable it if you still want to use it) and the issue should be gone.
That add-on has some code that runs when an object moves, and somehow it's got into a broken state and is trying to update the object positions when you're trying to move them. The problem seems to keep occurring in different versions of blender because the properties that are related to the broken state are stored in your file. Disabling the add-on removes these properties and if it is re-enabled it will set them up afresh in a working state. At least, that's what seems to be happening.

By the way, while that does solve that issue, there are still some other issues in your file, related to the drivers you have set up in the compositor in each of your scenes (which may have been set up by the add-on?). The System Console (Window> Toggle System Console for Windows users) prints out a lot of errors when you change scenes and a lot of the drivers seem to have missing references to objects.


text:
Trying to drive values with custom properties
I'm trying to drive the Lens property (focal length) of a camera with a custom property, to constrain it to a range (in this case, between 70 and 200mm). When this value goes from 70 to 200, I also want to be able to move an Empty that the camera is targeted to slightly up and down in Z (when the camera is at 70mm the vertical framing is right, but when it goes to 200 the empty is too low so the top of the subject is cropped out of frame).
I've added a custom property on the camera called "Zoom" - Blender gives its full data path as bpy.data.cameras["Cam_tight"]["Zoom"]. Adding a driver to the focal length property, set to Scripted Expression with values as below, doesn't work. (I can't even paste anything into the Path box, I have to type the path in manually.) What am I doing wrong? (I'm on 2.93.2 fwiw.)

I think that, because Prop already indicates Cam_tight as the target object (and so already has a reference to the target object), you should only need to give the name of the property itself, like: ["Zoom"] rather than bpy.data.cameras["Cam_tight"]["Zoom"]

Relatedly, if you Copy Data Path on the "Zoom" custom property and paste it into the driver's Path section, I believe you'll get exactly ["Zoom"]. This is how I normally build similar drivers

that's what I thought, but ["Zoom"] on its own doesn't seem to work. And I can't paste anything into the Path box anyway for some reason. It should work and it's how I've seen others do it but it may need some bashing of head on desk for a bit

It should work though. Make sure you added the custom property to the OBJECT (orange rectangle in the properties editor) and not the CAMERA (green camera icon in the properties editor). And it's case sensitive

@Gorgious that's amazing, it works now (just with ["Zoom"] for anyone interested or trying to do the same thing). So custom properties don't work if they're not added in the orange OBJECT tab?

Yes they do, but you have to change what's called the "ID type" beforehand. https://i.sstatic.net/u3i93.png You can add custom props to pretty much all ID Types. https://i.sstatic.net/uMm0D.png

@Gorgious Could you add this as an answer?

@RobertGützkow Sure :)

In Blender you can add custom properties to all objects that derive from the ID Type. You can also add custom props to Bones.
These types can be found by expanding the enumerator in the driver interface :

Usually you can find the custom properties interface in the far bottom of the ID type properties panels.
A camera object can have custom properties tied to its Object type (basically the data container) :

And its Camera type, where all the camera-related attributes can be tweaked :

Those props, although they share the same name, are in fact different objects and are not accessed the same way.
Here's how to access the Object custom property :

and the Camera custom property :

Note : The custom properties are case sensitive and they must be encased in double quotes and brackets : ["prop"]. Since you are writing a path relative to the selected object, you don't need to specify for instance bpy.data.objects["Camera"] beforehand.

in blender 4.2: data["prop"]


text:
Crashing with a cached simulation nodes setup
Just cached 1800 frames of a simulation nodes sim. It chugged through them fine (each .blob file is max about 30Mb) but as soon as it had finished the frame range, it crashed. Opening the file makes Blender instantly exit, -pof-. If I delete or move the .blob files, I can open the .blend file fine.
Is there a limit to how much of a cache Blender can cope with? I previously managed to cache the sim fine with the particle life set to a lower value, so there were fewer particles in total (although the .blob files were nearly the same size - max 28Mb).
I've tried this on 4.0.2 and 4.1. System is 128GB RAM, RTX 4090, Ryzen Threadripper 3960X 24-Core cpu.

Probably this is the answer but not  a positive one https://blender.stackexchange.com/questions/102149/multi-core-threaded-particle-simulations

Thanks. Is this a CPU issue though? It averages about 1-2 seconds per frame it's simulating, and it only crashes when trying to retrieve the baked data from the cache. Plenty of free space on the cache ssd too

So fwiw I've done some more tests. I went back to an earlier version of this file, which was set up to render in Cycles, and uses Set Point Radius to render the points as spheres, rather than Instance on Points as I've done in the above Eevee setup.
The original file has about 1.9m points, and the cached .blobs are ~160Mb per frame. This doesn't crash, and displays pretty much in realtime in the viewport. The Eevee version, instancing spheres on a point cloud of ~160k points, won't even load the cache without crashing Blender.
How can I render out points directly in Eevee?

I should mention that overall I'd rather use Eevee to render a final version as it's obviously much faster, and I have ~5500 frames to output

FWIW: This was a RAM issue. I upgraded to 256GB and it chugged through fine. It seems simulation nodes are not very memory efficient in Blender yet, as the amount of RAM used scaled proportionally with the overall size of the cache, rather than Blender just keeping the most recent framestate in RAM.


text:
Trying to clone some objects along a path (2.9.2)
I'm trying to do something similar to the lights around the edge of the Vegas sign, which would be really easy with the Cloner in c4d... I don't want them to deform (so Array + Curve seems to be no good) and I've tried cobbling something together in Geometry Nodes but I can't get the objects to align to the path normals: they all face the same way. Some solutions I've seen suggest doing it with Python - surely that's not necessary??

he doesn't want them to deform, so the curve modifier is not a solution. That's what he wrote.

Thanks Emir - that works partially, but the objects I'm cloning are all facing the same way (not along normals or tangents) and there's also no option to clone them along the shape - it obviously just puts one at each vertex, which isn't quite what I'm after. Someone needs to write a Cloner add-on maybe!

V.similar  https://blender.stackexchange.com/questions/161169/adding-festoon-lights

@batFINGER, oh nice, Robin Betts' answer uses the particle system to 'emit' the light bulbs instead of face instancing.

@NickHill You could do this with geometry nodes but the amount depends on the amount of vertices

Move the 3D cursor to the origin.
Create a plane. In edit mode scale it down so it's about the size of the base of one of your lights.
Create a light, move it around in edit mode so sits on the plane from step 2.
Parent the light to the plane. Then set the light to hidden.
Create your Bezier curve path.
Add an array modifier to the plane. Set it to "fit to curve," using the curve from step 5. Change from "relative offset" to "constant offset" and set the x value to the distance you want between lights.
Add a curve modifier to the plane using the curve from step 5.
In the plane's Object Properties, set Instancing to "Face".

The selected face is the only face in the object. The light bulb shows up with its origin in the center of the face and its rotation aligned to the face normal.

This is the final modifier stack for the plane.

Super answer!   It is so odd that there is not a simple "Align to Face Normal" in Instancing::Faces

The curve modifier affects the geometry of the object it's placed on, which is a good thing sometimes. In this case we don't want the light bulbs distorted, so I used the instancing trick. The light bulb aligns to the plane's normal without distortion.

really nice trick with the instancing! Learnt again a lot today! ;)


text:
how can i lower my hdri lighting strength
how can I lower my hdri lighting strength to almost 0? I'm making a 1 shot timelapse style from daytime to night fall in one shot. I attached my shader web for my world shader.

Turn down the Background node value from 1.2 down to 0. You can keyframe this if you want to transition from 0 to something bright. Hopefully that answers your question.

thank you @tester


text:
how do i remove hdri image from reflections. [Image added]
I want to keep the reflections from other meshes but remove the hdri image from reflecting. I just want to use the hdri for lighting. image shows what I want showing and not. green good red bad.
using version 2.93.1

Try this node setup for your world: Mix your HDRI with the color (or other HDRI) you want to see as reflexion, and use an Input > Light Paht > Is Glossy Ray as factor of your Mix Shader:

If you don't want to see the HDRI as background either, I guess you need to mix your Mix Shader with another one and this time use the Is Camera Ray output. But it looks like you've enabled the film Transparent option.

Thank you moon!


text:
how would i render a normal map of a model?
let's say I have a bunch of rope models (all the deep crevices and spirals. multiple ropes together). I want to take that rope bundle and get the height data from that scene as a normal map.

Hi :). Sounds like a simple normal map baking. There are many tutorials on that topic, it's not complicated :))

time to do some baking


text:
Why does adding an object to a collection with Python not remove it from its old collection?
I'm really new to Blender, and want to script an octahedron with all parts neatly placed inside its own collection.
But somehow, when I create a new collection and link objects to my newly created collection, the objects also stay linked to the original "Scene Collection".
In a new scene, when I drag and drop a manual added object to the scene, that I than add to the personal collection this does not happen?

myCollections = bpy.data.collections

colOcta = myCollections.new('col_Octahedron')
bpy.context.scene.collection.children.link(colOcta)

vtxAmount = 6
vtxPositions = [(0, 0, 10), (10, 0, 0), (0, 10, 0), (-10, 0, 0), (0, -10, 0), (0, 0, -10)]
for i in range(vtxAmount):
    iSolve = i + 1

    nowPos = vtxPositions[i]
    myX = nowPos[0]
    myY = nowPos[1]
    myZ = nowPos[2]
    #print(myX)
    newObj = bpy.ops.mesh.primitive_uv_sphere_add(radius=1, enter_editmode=False, location=(myX, myY, myZ))

    myObj = bpy.context.object
    myObj.name = "obj_Sphere%s" %iSolve
    myObj.data.name = "dat_Sphere%s" %iSolve
    grpOcta.objects.link(myObj)

An object can be linked to multiple collections by design.

then in larger projects the Scene Collection is one big messy thing with objects, sad... i like to have clean outliner...
how do i make it clean and proper

You'll have to unlink it from its old collection.

i tried doing that...
bpy.context.scene.collection.children.unlink(myObj)
TypeError: CollectionChildren.unlink(): error with argument 1, "child" -  Function.child expected a Collection type, not set

Got it...
bpy.context.scene.collection.objects.unlink(myObj)

An object can be part of an arbitrary number of collections. Adding an object to a collection does not remove it from any other collection it may be a part of.
When you use an operator to instantiate an object, is is automatically added to the active collection. In your case, to the Scene collection. To remove it from the scene collection, use :
bpy.context.scene.collection.objects.unlink(obj)

You can also use :
bpy.data.collections["My Collection"].objects.unlink(obj)

If you happen to know the collection name.
To iterate over all the collections the object is linked to, use obj.users_collection :
for collection in obj.users_collection:
    collection.objects.unlink(obj)

Note : If you remove an object from all collections in the active scene, the object will disappear from the outliner and you will have to dig into the orphan data or the file data to retrieve it.


text:
Why is the scaling point not in the middle of my selection?

When I'm modelling, why does this happen? When I want the two faces to scale in the middle, the point from where the scaling happens is on one side, so when I scale it becomes weird.

Hi. This should help with taking screenshots: https://www.take-a-screenshot.org You can use the [edit] link under your question to replace them.

You can select from which origin point to apply the scale using transform pivot points. They are at the top of your 3D view.
Right now I can see that your transform pivot point is set to "active element" which means you are scaling relatively to the center of the left face.
I am not sure what exactly you are trying to achieve but I suggest using "individual origins".


text:
In blender 2.8 there is no game engine or game logic
I want to design the game in which,when the key press from keyboard then it's should action... For example I want to move  the object with w a s d... How can I use in blender 2.8

As you've noticed yourself, Blender doesn't come with a game engine anymore. Therefore you will have to use another software to create the game. However you can use Blender to create the models, textures and animations. Game engines that you could potentially use are, e.g. Godot, Unity, Unreal Engine or UPBGE.

Why blender doesn't come with a game engine anymore???

https://blender.stackexchange.com/questions/106972/what-will-happen-with-blender-2-8-game-engine


text:
Is it possible to convert any mp4 file to hdri format to use in blender background
I am using blender 2.8 to animate drones effect.
In shading mode i am trying to add background to drones using hdri files ,but hdri files are limited in internet ,i want to use my own video shooted from camera .
How to achieve this, attaching screenshot of the blender process which i am following.

No I don't you might be able to do it with an image sequence.

Any online tool to convert image sequence to hdri.?

You can use simple picture or video files as sphere panorama background, you don't need to convert it to hdri. Just add them as Environment Texture.