Alembic Not Transferring Materials Per Frame #52240

New Issue

Atomic · 2017-08-01T16:53:12+02:00

Atomic commented

2017-08-01 16:53:12 +02:00

System Information
windows 10 gtx1070

Blender Version
2.79 test
Worked: (optional)

Short description of error
Testing 2.79 ability to read Houdini exported Alembic Files.

This image shows the mesh cache transfers ok. Smoothing is being transferred from frame to frame correctly.

However there does seem to be a bug in the material transfer from frame to frame. This mesh has multiple materials. I setup my materials on frame 1. Then when I move to a new frame and the material in slot 1 is applied to the entire mesh. Blender should relay the materials found in each material slot on frame #1 through out the timeline.

Exact steps for others to reproduce the error
Alembic_Material_Transfer_Issue.zip
Just open the attached blend and change the frame. I have included a 12 frame version of the .abc file shown in the GIF. When the frame changes the entire mesh is colorized with the value in material slot 1.

**System Information** windows 10 gtx1070 **Blender Version** 2.79 test Worked: (optional) **Short description of error** Testing 2.79 ability to read Houdini exported Alembic Files. This image shows the mesh cache transfers ok. Smoothing is being transferred from frame to frame correctly. ![biped_flip.gif](https://archive.blender.org/developer/F689183/biped_flip.gif) However there does seem to be a bug in the material transfer from frame to frame. This mesh has multiple materials. I setup my materials on frame 1. Then when I move to a new frame and the material in slot 1 is applied to the entire mesh. Blender should relay the materials found in each material slot on frame #1 through out the timeline. **Exact steps for others to reproduce the error** [Alembic_Material_Transfer_Issue.zip](https://archive.blender.org/developer/F689185/Alembic_Material_Transfer_Issue.zip) Just open the attached blend and change the frame. I have included a 12 frame version of the .abc file shown in the GIF. When the frame changes the entire mesh is colorized with the value in material slot 1.

Atomic commented

2017-08-01 16:53:12 +02:00

Changed status to: 'Open'

Atomic commented

2017-08-01 16:53:12 +02:00

Added subscriber: @AtomP

Sybren A. Stüvel was assigned by Bastien Montagne

2017-08-01 22:44:07 +02:00

Atomic commented

2017-08-05 20:21:29 +02:00

I tried again at transferring a Houdini based animation to Blender via the Alembic file format. I discovered that if I actually give every Houdini object I want to transfer an attribute called name that Blender will create a Blender object for each Houdini object named. This solves the multiple material transfer problem I encountered previously as long as each object has only one material.

This test also shows that you can transfer animated color information from Houdini to Blender as shown in the changing color of the fluid. However, this animated attribute transfer only seems to work for a few hard coded attributes in Blender (i.e. Cd). Arbitrary attribute import does not seem to be supported yet (i.e. my_float).

I'm an not sure if this should still be considered a bug. But some instructions may need to be offered to end users on how to prepare objects in their host application before exporting an Alembic file for use in Blender.

I tried again at transferring a Houdini based animation to Blender via the Alembic file format. I discovered that if I actually give every Houdini object I want to transfer an attribute called *name* that Blender will create a Blender object for each Houdini object named. This solves the multiple material transfer problem I encountered previously as long as each object has only one material. This test also shows that you can transfer animated color information from Houdini to Blender as shown in the changing color of the fluid. However, this animated attribute transfer only seems to work for a few hard coded attributes in Blender (i.e. *Cd*). Arbitrary attribute import does not seem to be supported yet (i.e. *my_float*). ![mocapbiped_fluid_walk_CD.gif](https://archive.blender.org/developer/F695307/mocapbiped_fluid_walk_CD.gif) I'm an not sure if this should still be considered a bug. But some instructions may need to be offered to end users on how to prepare objects in their host application before exporting an Alembic file for use in Blender.

Sybren A. Stüvel commented

2017-08-09 11:58:23 +02:00

I can confirm this as a bug.

rendered-viewport0001-0012.mp4

Here I've imported your ABC file (F689185) into Blender (8c488cb97f), set viewport colours for the materials, and dragged the geo_EXPORT object to camera left. That object shows the problems material problems, whereas the geo_skin object works just fine. A bit more digging shows that geo_EXPORT changes its number of vertices during the animation. This causes Blender to rebuild the mesh, after which the materials aren't applied any more (causing the default to the first material slot).

I can confirm this as a bug. [rendered-viewport0001-0012.mp4](https://archive.blender.org/developer/F701907/rendered-viewport0001-0012.mp4) Here I've imported your ABC file ([F689185](https://archive.blender.org/developer/F689185/Alembic_Material_Transfer_Issue.zip)) into Blender (8c488cb97f0c), set viewport colours for the materials, and dragged the `geo_EXPORT` object to camera left. That object shows the problems material problems, whereas the `geo_skin` object works just fine. A bit more digging shows that `geo_EXPORT` changes its number of vertices during the animation. This causes Blender to rebuild the mesh, after which the materials aren't applied any more (causing the default to the first material slot).

blender-admin commented

2017-08-09 13:05:22 +02:00

This issue was referenced by 45d7513f84

This issue was referenced by 45d7513f84bd3f3ee52207d4373e2ff980c954aa

Sybren A. Stüvel commented

2017-08-09 14:01:02 +02:00

Changed status from 'Open' to: 'Resolved'

Sybren A. Stüvel closed this issue

2017-08-09 14:01:02 +02:00

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Alembic Not Transferring Materials Per Frame #52240