Velocity not exported from Maya, causes crash

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Select the object to export from AbcExport and export using:
AbcExport -j "-sl -uv -wfg -fr 0 24 -a motionVectorColorSet -file C:/test.abc"
2. Import using AbcImport "C:/test.abc"
3. Render using mental ray with a 2D Motion Vector pass (mv2DToxik) to a 
half-float multi-channel EXR

What is the expected output? What do you see instead?
A rendered motion vector pass into the EXR. Maya has a fatal error crash with 
no information instead.

What version of the product are you using? On what operating system?
Alembic 1.0.4 (and tested 1.0.3), Windows 7 64-bit, MSVS Express 2008 SP1 + 
Windows 6.1 SDK x64, Autodesk Maya 2012 64-bit Hotfix 4.

Please provide any additional information below.
The mesh I am exporting is a RealFlow .bin stream which does have motion vector 
data. If I export without the -a motionVectorColorSet the scene doesn't crash 
but there is nothing drawn to the motion vector pass.

If this is the wrong approach then is it possible to export velocity with 
another approach with AbcImport/AbcExport from Maya?

Thanks!

Original issue reported on code.google.com by alex.ful...@ambiencedigital.com on 10 Feb 2012 at 12:37

[GoogleCodeExporter]

Could you provide a simple scene which has this data filled in?

The approach isn't terrible, but will only work without any hints in a Maya to 
Maya workflow.  motionVectorColorSet is being written out as an arbitrary 
geometry parameter, and not as velocities on the mesh.

Original comment by miller.lucas on 10 Feb 2012 at 12:57

[GoogleCodeExporter]

Hello Lucas,

From further study it looks like I'm just dealing with a special case, page 14:
http://www.realflow.com/documentation/realflow-maya.pdf

It looks like there's some kind of workaround being applied and not storing 
motionVectors as an attribute, it would explain the crash. I tried sampling at 
0.5:
AbcExport -j "-sl -uv -wfg -fr 26 70 -step 0.5 -file c:/temp/motion.abc";

It doesn't crash but it doesn't render them either, so I guess I'll need to 
work with some other solution, ideally I think realflow should add alembic 
support. :)

I can send you the abc but I think the realflow plugin does something weird, 
should I send the -step 0.5 abc or the -a motionVectorColorSet? (btw the new 
velocity in 1.0.4, is that exposed yet and if so, can I enable it somehow?)

Original comment by alex.ful...@ambiencedigital.com on 10 Feb 2012 at 1:27

[GoogleCodeExporter]

Hello Lucas,

After further investigation I noticed the -wfg flag was set, removed that and 
kept -step 0.5 on there and let realflow calculate the subframes and now 
alembic exports correctly, and also renders a motion vector pass correctly, so 
I didn't need to extract any motion vector attributes.

Sorry about this, it works well now thanks for the reply.

Original comment by alex.ful...@ambiencedigital.com on 13 Feb 2012 at 12:02

[GoogleCodeExporter]

Original comment by miller.lucas on 14 Feb 2012 at 2:34

• Changed state: Resolved