Maya, exported blendshapes curve tangent problem

Alex_J

Using Maya 2018 and exporting to Marmoset Toolbag 4

I am trying to figure out why the tangents in my graph editor will not export correctly.

I make the splines so that they go into negative values on the blendshape node. This plays correctly in the Maya viewport, resulting in a squash and stretch.

Upon export I receive this warning. I believe its pointing directly to the problem but I'm not sure how to interpret it. The result in Toolbag is that the blendshapes play but only in the Positive values. I get the stretch, but no squash.

If it helps, here are my animation settings.

If anyone can help me I appreciate it very much. Thanks. I'm going to have to read maya docs in the meantime and try and figure out what some of this stuff means.

Alex_J

@Eric Chadwick ,

is it possible to move this to the marmoset forum? Thank you.

I got some help from maya area forums that might narrow things down:

If I export a sphere with blendshape animations that go from positive to negative values as an fbx, only the positive blendshape values will play in Toolbag.

If I export same sphere as alembic file, the full range of blendshape values will play during animation.

But exporting as alembic wont fit my workflow, so the question is, why does alembic support the negative blendshape values but fbx will not?

Eric Chadwick

Moved.

However this sounds like a limitation of FBX or that particular exporter. 

What happens if you reimport the FBX back into Maya? I suspect the exported file itself is the problem, rather than Toolbag's importer.

Alex_J

@Eric Chadwick ,

I just tried your suggestion (exporting as fbx and reimport back into maya) and the animation works as expected in Maya.

I also just tried upgrading to Maya 2020, and also tried in Toolbag 3 rather than 4, all without a difference.

I've also reset the maya export preferences to default with no change.

So far the only way to get negative blendshape values to show in Toolbag have been by exporting as an alembic file type.

EarthQuake

Negative blendshapes are likely an untested/unsuported case in Toolbag, if you can email example files to support@marmoset.co we can look into this more.

As to why Alembic would support this: Alembic is a cached geometry file format that saves unique vertex data per frame, anything you can rig up will work with Alembic because it is agnostic to technique or feature set, it's just a simple dump of vertex data.

Alex_J

@EarthQuake , thanks I will send that.

Alex_J

I work alone so I am not familiar with animation best practices. Is it uncommon to use negative blendshapes? Perhaps I should just use extra joints as necessary?

The purpose was for adding squash and stretch to muscles/fat on human characters. Making use of the negative value makes it easy to get realistic jiggles using the graph editor.