Hi all,

I’ve been stuck struggling with this for the past 3 days, and am at the end
of my rope. The glslShader plug-in that ships with Maya demonstrates that
it does work (see bottom of README), but I can’t get it to work outside of
that plug-in.

   - https://github.com/mottosso/mayaGeometryShader

What happens?

The pixel shader just seems to stop getting input with a geometry shader in
the mix. I’ve tried simply passing data from the vertex to pixel shader via
the geometry shader, but for some reason having the geometry shader in the
mix completely kills any drawing, without throwing any error.
Why do this?

Ultimately, I’d like to do as much of my plug-in development as possible in
Python, and drawing is currently the main culprit when it comes to
performance. I’d like to offload some of that burden to GLSL, and draw both
geometry and gizmos and visualisations of all kinds by passing tiny amounts
of data from Python to OpenGL.
Why not just use the glslShader plug-in?

   1. It is highly unoptimised; made for experimenting with shaders rather
   than actually using it in production on many nodes.
   2. It is dynamic; the attributes are dynamically generated based on the
   contents of the ogsfx file, making scripting towards it that much more
   tricky.
   3. It is a shader, rather than a node; which means each one of my custom
   nodes need an additional node that go with it. More to manage is bad news.
   4. It requires geometry. I’d like to use a geometry shader to draw
   simple shapes, i.e. plane, box, sphere and capsule, using little to no
   actual geometry in Maya. This example is almost there, filling the OpenGL
   buffer directly without the aid from Maya.
   5. It doesn’t work in non-textured mode. The drawn geometry is meant to
   look like any other geo, and should exist in textured and non-textured mode
   alike.

Hmm.
What could be the cause?

My theory is that there is something I’m not passing along. The glslShader
example passes “geometry requirements” and “mutators” into the mix that
I’ve yet to fully understand. Another theory is that I also need a “control
shader”, and although the TesselationExample does include those, the
SilhouetteExample does not and it also works just fine.

Anyone know what’s going on?

Best,
Marcus

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