Hi… having a little trouble with krakatoa particles and scene geo in Maya, want to confirm the workflow for shadows and holdout objects.
Building a shockwave like effect with an object entering from above, descending, and making contact with a ground plane. Dust particles are stirred up and blow out in a circle away from the object. Using a PRT loader with 100 passes to get the density desired and the dust particles look great. Now comes the next step: contact shadows particle to ground, and a holdout of the descending object.
From looking at the boards/google a potential way to get a shadow pass in Maya is to make a proxy for the ground out of a VOL object. Would I override the particle color of the dust and ground particles to white? How do you just get the ground (VOL) to receive shadows and not get the dust self shadowing, or is that not possible and the best one can get is a shadow pass of both ground and dust?
I added holdout geometry for the ground object and it worked fine when rendering the dust, however when I added the geo of the descending object group as holdout matte objects it appears to make no difference, the particles that are behind the holdout still are visible. Are there any requirements or special preparations that need to be done to holdout geo to get it to work? The ground geo is a single triangulated mesh (since it was also exported to realflow) but the entering geo is quads and multiple meshes grouped together. I selected the meshes that form the overall volume to be occluded and added them both as a group, and then as individual meshes, but neither has them actually occluding the dust particles.
Any advice for properly casting shadows and creating occlusion geometry would be greatly appreciated.