Points (point cloud) materials

Although primitives with mode POINTS (point clouds) are loaded properly, the materials created (for URP, HDRP and BiRP) do not render points properly.

Points should be rendered as mentioned in the glTF spec.

[atteneder]

Update: PR #495 brought the necessary API change to create material generators with point cloud material support!

[atteneder]

Ah. Does this mean normal HLSL shaders?

Yes!

If so, here are two that might be a useful starting point: https://gist.github.com/camnewnham/290fd777d7b04775f7ad98bbd3ced40f

* Billboard geometry shader that renders uniform screen size points and vertex colors

* Basic vertex color shader that renders pixel sized points on the platforms I've tested; but since gl_PointSize is not supported and generally seems to be considered legacy this size doesn't appear modifiable.

The basic vertex shader is of course much faster to run than the geometry shader.

Thanks for the reference. Those won’t work on platforms without geometry shader support though. Also it’s just a solution for Unlit materials (glTF spec says full pbrMetallicRougness should work with points/lines as well).

I’ve also found that for points to render they seem to need an identity index buffer [ 0, 1, 2, 3, 4, 5, … ].

True, if you use the shaders you proposed.

Step one would be to extend IMaterialGenerator.GenerateMaterial with a parameter that depicts the targeted mesh topology (or alternatively add a IMaterialGenerator.GeneratePointMaterial). The respective MaterialGenerator can then pick another shader, based on platform. Now this is a bit impure, as primitive to material is a many-to-one relation (you could theoretically use a glTF material on both a triangluar primitive and a point primitive), but I’d ignore this special case. Its a rare corner-case and one can easily sail around it by not re-using materials in that way.

I’ll schedule this API change, but not sure when/if I’ll find time to implement and test the shaders.