Pose logic exhibiting div-by-zero behaviour #61905

New Issue

shannon zachow · 2019-02-24T08:33:41+01:00

shannon zachow commented

2019-02-24 08:33:41 +01:00

System Information
Operating system: Linux
Graphics card: GTX 1050

Blender Version
Broken: version: 2.80 (sub 45), branch: blender2.7, commit date: 2019-02-22 22:26, hash: 779860d34e, type: Release
build date: 2019-02-23, 00:06:29

Short description of error
Random subset of vertices disappear from rigged-object when exiting Edit_Mode.

Exact steps for others to reproduce the error
system-info.txt
system-info.txt

mouth.blend
mouth.blend

Using the attached file "mouth.blend"
(this is a rigged mouth -- it's meant to be Boolean_Difference'd from the head of a character).

Go into/outof Edit_Mode on the object Mouth.
The "lost" vertices almost always re-appear when entering Edit_Mode.

The vertices do not always disappear when exiting Edit_Mode... sometimes toggling the Mouth object's SubSurf-Modifier's Viewport_Display mode while in Edit_Mode can help to trigger the disappearing vertices. Sometimes changing the Pose or clearing the Pose changes whether or not the vertices disappear.
Exactly which vertices do disappear sometimes changes. Most often, it was those in the +X,-Z quadrant.

Sometimes the vertices merely disappear. Sometimes their coordinate values become HUGE numbers (div-by-zero) and the Mouth object is drawn with some parts stretching off to infinity in different directions.

I've been chasing this issue for over a week. I have changed and re-modeled the Mouth object in many different ways, and even went so far as to export to a .dae file, then import and rebuild the whole thing. None of these removed the problem.

  - > I just finally tried tweaking some of the bones out of exact-linear-alignment, and that fixed the problem (made it impossible for me to reproduce the disappearing-vertices issue). Re-aligning the bones brought the problem back, so I thought that someone might be able to check the responsible code.

The opening of the mouth is the tongue-like appendage protruding along -Y.
Each quadrant of this part has 3 bones: LipTop.A.L --> LipTop.bendy.L --> LipTop.B.L
(where {Top | Btm} and {.L | .R} )
every .bendy bone starts at a .A, and Bone_Constraint "Stretch_To" a .B .
The bones .A and .B are set as TANGENT start|end Handles for the .bendy bone between them.

When the tail of the .B bones (ie; LipTop.B.L) is exactly in line with the head & tail .A and the head of .B, then the vertices will disappear.

If I select the tails of all 4 .B bones in Armature Edit_Mode, and slightly offset them (ie; G Y .001), then the disappearing vertices problem goes away.

It is my guess that somewhere in the code to apply the pose of a Bendy_Bone with TANGENT handles, there is a "divide by the angle between the two handles".

Yes: I will just offset the bones slightly to avoid the problem now.
But working on magically disappearing vertices, or vertices that smeared out to infinity, however, has been a big time sinkhole. Can the code handle this edge-case better? Or is there a better way to inform users what the problem is?

thank you!

**System Information** Operating system: Linux Graphics card: GTX 1050 **Blender Version** Broken: version: 2.80 (sub 45), branch: blender2.7, commit date: 2019-02-22 22:26, hash: 779860d34e26, type: Release build date: 2019-02-23, 00:06:29 **Short description of error** Random subset of vertices disappear from rigged-object when exiting Edit_Mode. **Exact steps for others to reproduce the error** system-info.txt [system-info.txt](https://archive.blender.org/developer/F6701881/system-info.txt) mouth.blend [mouth.blend](https://archive.blender.org/developer/F6701888/mouth.blend) ![Screenshot at 2019-02-24 01-49-06.png](https://archive.blender.org/developer/F6701895/Screenshot_at_2019-02-24_01-49-06.png) ![Screenshot at 2019-02-24 01-48-27.png](https://archive.blender.org/developer/F6701898/Screenshot_at_2019-02-24_01-48-27.png) Using the attached file "mouth.blend" (this is a rigged mouth -- it's meant to be Boolean_Difference'd from the head of a character). Go into/outof Edit_Mode on the object Mouth. The "lost" vertices almost always re-appear when entering Edit_Mode. The vertices do not always disappear when exiting Edit_Mode... sometimes toggling the Mouth object's SubSurf-Modifier's Viewport_Display mode while in Edit_Mode can help to trigger the disappearing vertices. Sometimes changing the Pose or clearing the Pose changes whether or not the vertices disappear. Exactly which vertices do disappear sometimes changes. Most often, it was those in the +X,-Z quadrant. Sometimes the vertices merely disappear. Sometimes their coordinate values become HUGE numbers (div-by-zero) and the Mouth object is drawn with some parts stretching off to infinity in different directions. I've been chasing this issue for over a week. I have changed and re-modeled the Mouth object in many different ways, and even went so far as to export to a .dae file, then import and rebuild the whole thing. None of these removed the problem. - > I just finally tried tweaking some of the bones out of exact-linear-alignment, and that fixed the problem (made it impossible for me to reproduce the disappearing-vertices issue). Re-aligning the bones brought the problem back, so I thought that someone might be able to check the responsible code. The opening of the mouth is the tongue-like appendage protruding along -Y. Each quadrant of this part has 3 bones: LipTop.A.L --> LipTop.bendy.L --> LipTop.B.L (where {Top | Btm} and {.L | .R} ) every .bendy bone starts at a .A, and Bone_Constraint "Stretch_To" a .B . The bones .A and .B are set as TANGENT start|end Handles for the .bendy bone between them. When the tail of the .B bones (ie; LipTop.B.L) is exactly in line with the head & tail .A and the head of .B, then the vertices will disappear. If I select the tails of all 4 .B bones in Armature Edit_Mode, and slightly offset them (ie; G Y .001), then the disappearing vertices problem goes away. It is my guess that somewhere in the code to apply the pose of a Bendy_Bone with TANGENT handles, there is a "divide by the angle between the two handles". Yes: I will just offset the bones slightly to avoid the problem now. But working on magically disappearing vertices, or vertices that smeared out to infinity, however, has been a big time sinkhole. Can the code handle this edge-case better? Or is there a better way to inform users what the problem is? thank you!

shannon zachow commented

2019-02-24 08:33:41 +01:00

Added subscriber: @shannonz-1

Jacques Lucke commented

2019-02-25 11:59:11 +01:00

Added subscriber: @JacquesLucke

Jacques Lucke commented

2019-02-25 11:59:11 +01:00

Are you able to reproduce the issue in an as-simple-as-possible .blend file?
Also give exact steps to reproduce the issue, please.

It's hard to understand the actual issue based on your text, for me at least.

Are you able to reproduce the issue in an as-simple-as-possible .blend file? Also give exact steps to reproduce the issue, please. It's hard to understand the actual issue based on your text, for me at least.

shannon zachow commented

2019-02-25 21:45:02 +01:00

Re: what is the actual issue?

Pose_Mode involving bendy_bones sometimes makes a random subset of object vertices not be displayed. Look at the 2 screenshot images: the Edit_Mode (1st) image shows what the shape should look like; Pose_Mode (2nd) image shows what it looks like when switching back to Pose_Mode, and this is the alt-R, alt-G pose.

There appears to be a problem in the Pose_Mode logic. When applying pose-math to vertex position, the computed posed position of a vertex either collapses to zero or explodes to infinity. -- in the example file I've given, the pose has not changed, therefore the pose image should look like the Edit_Mode image, instead, almost half of the object has disappeared.

Re: what is the actual issue? Pose_Mode involving bendy_bones sometimes makes a random subset of object vertices not be displayed. Look at the 2 screenshot images: the Edit_Mode (1st) image shows what the shape should look like; Pose_Mode (2nd) image shows what it looks like when switching back to Pose_Mode, and this is the alt-R, alt-G pose. There appears to be a problem in the Pose_Mode logic. When applying pose-math to vertex position, the computed posed position of a vertex either collapses to zero or explodes to infinity. -- in the example file I've given, the pose has not changed, therefore the pose image should look like the Edit_Mode image, instead, almost half of the object has disappeared.

shannon zachow commented

2019-02-25 22:18:12 +01:00

Here is a much simpler file that reproduces the problem.

test007.blend

Steps to reproduce problem:

Select Armature
Tab to Pose_Mode
Tab to Object_Mode
Select Object
Tab to Edit_Mode
Tab to Object_Mode

At this last step the object should disappear.
If you look in the N-side-panel, the Object's Dimensions have become like 20-digit numbers.

Here is a much simpler file that reproduces the problem. [test007.blend](https://archive.blender.org/developer/F6714004/test007.blend) Steps to reproduce problem: Select Armature Tab to Pose_Mode Tab to Object_Mode Select Object Tab to Edit_Mode Tab to Object_Mode At this last step the object should disappear. If you look in the N-side-panel, the Object's Dimensions have become like 20-digit numbers.

Jacques Lucke commented

2019-02-26 13:35:20 +01:00

Thanks! Now I can reproduce the issue.