For my current game project, I need to export my meshes in GLTF or GLB. For this, I've been using the 'ROP GLTF Output' node, and principled shaders for the materials. The issue I'm running into is that the point Alpha attributes don't seem to export.


The point color does export correctly, de opacity works as intended in the Houdini viewport, and I've followed the instructions from the 'Import and export GLTF [www.sidefx.com]' documentation page about the Alpha blend settings, but once I import the mesh in - for example - Blender, the opacity is just one constant value across the whole mesh (which matches the value of the opacity with the point Alpha turned OFF in Houdini), as if it ignored the point attribute.

Is there anything else I should be doing to export the opacity/point Alpha properly or is this just not supported?

This is something that will be fixed in the next major release of Houdini. The fix ensures that the Alpha attribute will be properly handled. Alpha will be exported to the 4th component of the color vec4 glTF attribute (and also imported from there).