"Stretch To" bone constraint doesn't work properly with "Scene Scale" (Metric Units). #44408

New Issue

Blendy · 2015-04-16T08:34:46+02:00

Blendy commented

2015-04-16 08:34:46 +02:00

System Information
Windows 7 64 bit and AMD HD6770 graphic card

Blender Version
Broken: (blender 2.74 or previous versions)
Worked: (not sure)

Short description of error

When the scene Metric Units has been set to 0.01, for example, create an armature and add a Stretch To bone constraint to a bone with a target bone, then switch around the Volume Maintain modes of constraint, or after resetting length, the bone with constraint will pop into a wrong length. Even "Reset" length button won't permanently fix it, once grabbing the target bone, the issue continues.
Stretch_To_scale_bug.blend

**System Information** Windows 7 64 bit and AMD HD6770 graphic card **Blender Version** Broken: (blender 2.74 or previous versions) Worked: (not sure) **Short description of error** ![stretch_to_scale_issue.png](https://archive.blender.org/developer/F162940/stretch_to_scale_issue.png) When the scene Metric Units has been set to 0.01, for example, create an armature and add a Stretch To bone constraint to a bone with a target bone, then switch around the Volume Maintain modes of constraint, or after resetting length, the bone with constraint will pop into a wrong length. Even "Reset" length button won't permanently fix it, once grabbing the target bone, the issue continues. [Stretch_To_scale_bug.blend](https://archive.blender.org/developer/F162947/Stretch_To_scale_bug.blend)

Blendy commented

2015-04-16 08:34:46 +02:00

Changed status to: 'Open'

Joshua Leung was assigned by Blendy

2015-04-16 08:34:46 +02:00

Blendy commented

2015-04-16 08:34:46 +02:00

Added subscriber: @Rays-Lv

Blendy commented

2015-04-16 08:50:10 +02:00

Additional: Maybe you should also check the other constraint types based on the same mechanism for this issue. I haven't tested them all.

blender-admin commented

2015-04-16 15:11:55 +02:00

This issue was referenced by 0b691563ea

This issue was referenced by 0b691563eaff385d23c4199c85dc47a188420284

Joshua Leung commented

2015-04-16 15:18:01 +02:00

Changed status from 'Open' to: 'Resolved'

Joshua Leung closed this issue

2015-04-16 15:18:01 +02:00

Joshua Leung commented

2015-04-16 15:18:01 +02:00

Closed by commit 0b691563ea.

Closed by commit 0b691563ea.

Joshua Leung commented

2015-04-16 15:20:59 +02:00

The problem here was that the property was hard limited to only having a maximum of 100 blender units (or 1m in the metric units you were using), so the rest length was getting clipped instead of being handled correctly.

I'm not sure how you ended up needing to make a 4m long bone, though it should be noted that you may run into other problems at this scale eventually.

The problem here was that the property was hard limited to only having a maximum of 100 blender units (or 1m in the metric units you were using), so the rest length was getting clipped instead of being handled correctly. I'm not sure how you ended up needing to make a 4m long bone, though it should be noted that you may run into other problems at this scale eventually.

Blendy commented

2015-04-17 03:23:36 +02:00

Added subscriber: @JoshuaLeung

Blendy commented

2015-04-17 03:23:36 +02:00

In #44408#303248, @JoshuaLeung wrote:
The problem here was that the property was hard limited to only having a maximum of 100 blender units (or 1m in the metric units you were using), so the rest length was getting clipped instead of being handled correctly.

I'm not sure how you ended up needing to make a 4m long bone, though it should be noted that you may run into other problems at this scale eventually.

Look, I need to export animated mesh to UE4 from blender. I tried a couple of methods to handle the scales correctly with UE4, however, the only way I found work properly is keep the Scale of FBX export options exactly same as Scene Scale in blender. Otherwise, the mesh and bones imported in UE4 from blender will be differently scaled. For example, when exporting FBX with scale 100 leaving scene scale default at 1.0 in blender, the mesh imported in UE4 will be 100 times larger than bones. But other softwares like maya got no issue about this. However, the recommended unit in UE4 is cm, for example, this means I must make a 200 units height character to make sure it'll look 2 meters height in UE4. If I make a few meters height monster, a single bone can easily be more than 100 blender units long. But as you said it's not allowed in blender, so, could you tell me a proper way to handle it?

> In #44408#303248, @JoshuaLeung wrote: > The problem here was that the property was hard limited to only having a maximum of 100 blender units (or 1m in the metric units you were using), so the rest length was getting clipped instead of being handled correctly. > > I'm not sure how you ended up needing to make a 4m long bone, though it should be noted that you may run into other problems at this scale eventually. Look, I need to export animated mesh to UE4 from blender. I tried a couple of methods to handle the scales correctly with UE4, however, the only way I found work properly is keep the Scale of FBX export options exactly same as Scene Scale in blender. Otherwise, the mesh and bones imported in UE4 from blender will be differently scaled. For example, when exporting FBX with scale 100 leaving scene scale default at 1.0 in blender, the mesh imported in UE4 will be 100 times larger than bones. But other softwares like maya got no issue about this. However, the recommended unit in UE4 is cm, for example, this means I must make a 200 units height character to make sure it'll look 2 meters height in UE4. If I make a few meters height monster, a single bone can easily be more than 100 blender units long. But as you said it's not allowed in blender, so, could you tell me a proper way to handle it?

Joshua Leung commented

2015-04-17 03:30:54 +02:00

Added subscriber: @mont29

Joshua Leung commented

2015-04-17 03:30:54 +02:00

Ah ok, I see... :)

You may want to ask @mont29 about these issues, since he's more familiar with the state of exporters

Ah ok, I see... :) You may want to ask @mont29 about these issues, since he's more familiar with the state of exporters

Bastien Montagne commented

2015-04-17 06:47:14 +02:00

I can’t say much… Scale handling by UE4 remains pitch black mystery to me, as you say FBX exported by Blender load OK under other app (personally checked with Unity, you say Maya is OK too), so…

Blendy commented

2015-04-17 10:57:34 +02:00

@JoshuaLeung
Thanks, I've reported the FBX scale bug to him.

But, not allowing a single bone larger than 100 blender units IS another problem. I can't understand why it must be designed like that. Since Blender had already supported various Metric Units, apparently, 100 units bone length limitation can't handle that any more. This section MUST be re-designed. However, the UE4's official animation workflow is also treating 100 units as 1 meter in Maya.

You can see this UE4's official sample character exported from engine project, it also looks very large in Maya (about 200 units height).

@JoshuaLeung Thanks, I've reported the FBX scale bug to him. But, not allowing a single bone larger than 100 blender units IS another problem. I can't understand why it must be designed like that. Since Blender had already supported various Metric Units, apparently, 100 units bone length limitation can't handle that any more. This section MUST be re-designed. However, the UE4's official animation workflow is also treating 100 units as 1 meter in Maya. ![maya_fbx.png](https://archive.blender.org/developer/F163433/maya_fbx.png) You can see this UE4's official sample character exported from engine project, it also looks very large in Maya (about 200 units height).

Blendy commented

2015-04-17 11:28:11 +02:00

In #44408#303468, @mont29 wrote:
I can’t say much… Scale handling by UE4 remains pitch black mystery to me, as you say FBX exported by Blender load OK under other app (personally checked with Unity, you say Maya is OK too), so…

@mont29
Hi, mont29. Thanks for replying here. The scale handling of Blender FBX exporter(and importer) actually works not perfect, About this, I'd opened another thread for you, please check it out: https:*developer.blender.org/T44424?workflow=create

> In #44408#303468, @mont29 wrote: > I can’t say much… Scale handling by UE4 remains pitch black mystery to me, as you say FBX exported by Blender load OK under other app (personally checked with Unity, you say Maya is OK too), so… @mont29 Hi, mont29. Thanks for replying here. The scale handling of Blender FBX exporter(and importer) actually works not perfect, About this, I'd opened another thread for you, please check it out: [https:*developer.blender.org/T44424?workflow=create ](https:*developer.blender.org/T44424?workflow=create)

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"Stretch To" bone constraint doesn't work properly with "Scene Scale" (Metric Units). #44408