Alembic import issue with multiple materials on a mesh #65959

New Issue

terry · 2019-06-20T16:51:37+02:00

terry commented

2019-06-20 16:51:37 +02:00

System Information
Operating system: Windows-10-10.0.10586 64 Bits
Graphics card: Geforce 860M/Intel(R) HD Graphics 4600 Intel 4.3.0 - Build 20.19.15.4624

Blender Version
Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-06-19 18:29, hash: d30f72dfd8
Worked: (optional)

Short description of error
loaded Alembic sample.
not showing materials correctly.
Also smoothing incorrect when shatter starts.

Exact steps for others to reproduce the error
Load Alembic.
Change material 2 to RED color.
scrub timeline to start of animation - see the mess.

Smoothing.
Load Alembic.
scrub till shatter happens.
see bad smoothing.

alembic.ABC

**System Information** Operating system: Windows-10-10.0.10586 64 Bits Graphics card: Geforce 860M/Intel(R) HD Graphics 4600 Intel 4.3.0 - Build 20.19.15.4624 **Blender Version** Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-06-19 18:29, hash: `d30f72dfd8` Worked: (optional) **Short description of error** loaded Alembic sample. not showing materials correctly. Also smoothing incorrect when shatter starts. **Exact steps for others to reproduce the error** Load Alembic. Change material 2 to RED color. scrub timeline to start of animation - see the mess. Smoothing. Load Alembic. scrub till shatter happens. see bad smoothing. [alembic.ABC](https://archive.blender.org/developer/F7365885/alembic.ABC)

terry commented

2019-06-20 16:51:38 +02:00

Added subscriber: @sanger.terry

terry commented

2019-06-20 16:52:24 +02:00

Alembic material/smoothing bug.

Brecht Van Lommel changed title from ~~Alembic bug~~ to Alembic import issue with multiple materials on a mesh

2019-06-21 13:28:07 +02:00

Sybren A. Stüvel was assigned by Brecht Van Lommel

2019-06-21 13:28:07 +02:00

Sybren A. Stüvel commented

2019-07-04 18:16:30 +02:00

I did some investigation, and the material assignment issue seems to be a problem with 3DS Max. The ABC file contains a material assignment per mesh face, using face indices to indicate which face has which material. These face indices are numbered incorrectly: they use the numbering from the faces after the mesh breaks apart (where it has 4372 faces), even for the frames where the mesh is still in one piece (and only has 968 faces).

As for the normals, this is a limitation of Blender. When the ABC mesh has face-varying normals, it discards the normals themselves and just enables smooth shading. Actually properly loading the normals is thus a new feature -- I'm working on a patch, but it won't be merged into 2.80.

I did some investigation, and the material assignment issue seems to be a problem with 3DS Max. The ABC file contains a material assignment per mesh face, using face indices to indicate which face has which material. These face indices are numbered incorrectly: they use the numbering from the faces after the mesh breaks apart (where it has 4372 faces), even for the frames where the mesh is still in one piece (and only has 968 faces). As for the normals, this is a limitation of Blender. When the ABC mesh has face-varying normals, it discards the normals themselves and just enables smooth shading. Actually properly loading the normals is thus a new feature -- I'm working on a patch, but it won't be merged into 2.80.

Sybren A. Stüvel commented

2019-07-30 17:08:55 +02:00

I'm closing this task, as the part that we can fix in Blender (the glitching normals) has been fixed in e9c149d911.

I'm closing this task, as the part that we can fix in Blender (the glitching normals) has been fixed in e9c149d911.

Sybren A. Stüvel commented

2019-07-30 17:09:09 +02:00

Changed status from 'Open' to: 'Resolved'

Sybren A. Stüvel closed this issue

2019-07-30 17:09:09 +02:00

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Alembic import issue with multiple materials on a mesh #65959