Re: [Maya2osg-users] Blend shapes

[Peter W. <pp...@cg...>]

Hi Javier,

fast answer, but details on mondy.


>    Hi Peter,
>
>    I'm going to export a 3D character with skeleton animation and blend
> shapes, so I will at last test the osgAnimation export  :)

I wasn't able to add Skinning Code till now, so all yo can export is 
transform animation. My osgMaya exporter has skinning implemented, but 
the merging will take some time, so I don't know how fast I'll get to this.
>    I want to ask you some questions about osgAnimation, the exporter
> and the process in general. I'd appreciate your advice and your
> knowledge here, as I had no previous experience here and I don't even
> know what is supported by osgAnimation and what is not.
>
>    Are blend shapes supported in Maya2OSG? Is there any development? Or
> may I have to start from scratch?

I started to write the export for that. I stopped as I was a little 
frustrated that you cannot't "chain" the skining and morphing in an osg 
file. Cedric showed me how to do this through code. But now I already 
know more about osg, and I have an Idea what has to be done.
Datails after monday

>    And about how to prepare the model, it is a pseudo-humanoid
> character (biped) that will have blend shapes applied only to the
> face. The artist is asking me whether she should cut out the head to
> create the blend shapes only there or keep the body geometry as a
> whole. Is it a problem to rejoin the blend-shaped head later with the
> rest of the body? Have you ever done it?

This is the "normal" way people do it in the industry. So for the 
begining it would be cool if she would keep the whole body mesh 
attached. Later we should add this functionality, but I don't know how 
far osgANimation needs to support this. Basically in normal morphing you 
blend the position of a point to the position of another point. You 
identify both points with their id. If you screw up point numbering in 
one of the meshes ( by deliting one Vertex somwhere ) you scre up the 
morphing. We would require a map between target and source ids. That we 
can do in the plug in, but can osgAnimation use such a map ? Not shure, 
but I don't think so.

>    In case of having the "blend-shaped head" and the body in separate
> geometries, both affected by the skeleton animation, as long as the
> vertices in the joint edges are not affected by blend shapes and have
> assigned the exact same weights in skinning, should it be a problem?
> Do you think it would produce visible cracks in this part of the
> geometry?

No, the way you normally di it is, cut the hayd off, but dont' morph the 
border edges. With this you guarantee continuity.
So always first morphing, than skinning in the deformation chain, but I 
think your artist knows that. So then the skin is derphonming the 
morphed mesh, and no cracks will be visible in the morph as well as in 
the skin.

Cheers, PP