renderstate vs packed fragments

[meeotch]

So am I correct in understanding that the Render State VOP can be used to read attributes on packed *geos* in a shader.  (Where "attributes" means attributes  you've added to the top-level packed points themselves, not the underlying packed geometry.)...  But that the same doesn't work with packed fragments?  Or is this a bug?

See attached file.  Render and inspect the "noiseColor" image plane.  If you turn on "create packed fragments" on the Pack node, and re-render, you'll notice that the shader is no longer rendering colors into this plane.

I understand that packed fragments are references into a larger geo, whereas packed geos are entire geos.  But I don't see why this would prevent you from using Render State with both of them.  If a technical explanation exists, I'd be glad to hear it.

packedRenderState.hip

[Skybar]

I found this in the docs:

Quote

Merge packed fragments into single geometry

Houdini render property

 

vm_pack_mergefragments

IFD property

 

object:pack_mergefragments

For efficiency, mantra usually merges separate fragments into a single piece of geometry. This typically uses less geometry and renders more efficiently.

However, since the geometry is merged into a single piece of geometry for rendering, the individual packed fragments are not available for material stylesheets and their attributes aren’t available for the renderstate() function.

Disabling this option will cause each fragment primitive to be rendered as a separate mantra object. This will typically take more memory and may impact rendering performance.

 

[meeotch]

Nice - thanks for the info.