Per-vertex color. in a custom RealityKit mesh? (macOS)

Question

Created Jun ’23

Replies 4

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I'm working on an application for viewing AMF models on macOS, using RealityKit. AMF supports several different ways to color models, including per-vertex color (where the color of a triangle is interpolated from vertex to vertex) as well as per-face color (where the color of the triangle is the same across the entire face).

I'm trying to figure out how to support those color models using a RealityKit mesh. Apple's documentation (https://developer.apple.com/documentation/realitykit/modifying-realitykit-rendering-using-custom-materials) talks about per-vertex colors, but I haven't found a way to create a mesh that includes per-vertex colors, other than use a texture map (which might be the correct solution).

Can someone give me some pointers?

Boost

Answer 1

rthart OP

Jul ’23

I also find the documentation difficult to follow. A full example of the triangle that is shown in the documents would be quite helpful.

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Answer 2

drewolbrich OP

Sep ’23

@raldrich Hi, did you ever figure this out? I am following this same path and I am surprised that MeshDescriptor does not appear to define a vertex color option. Maybe the answer is to define a custom buffer and then, at least on visionOS, hope that it's possible to define a shader graph that accesses the custom buffer.

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Answer 3

Graphics and Games Engineer OP

Apple

Sep ’23

Hi @hhjgjhghjghjghjg you might be able to get vertex colors to work with something like

let vertexColor: MeshBuffers.Semantic = MeshBuffers.custom("vertexColor", type: SIMD4<Float>.self)
let meshResource = MeshDescriptor()
meshResource[vertexColor] = ...

1

Answer 4

avitzur OP

Mar ’24

I've been unsuccessful so far. If anyone has gotten RealityKit to handle a vertexColor buffer to work, please provide some more details.

1