How do I pass data to the CUSTOM built-in in a particles shader?

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:bust_in_silhouette: Asked By Charlie

I have a bit of experience passing per-vertex data to spatial shaders using ArrayMesh arrays (getting vertices to do stuff based on their own data*). However, my need now is more in line with particles. There is a particles shader built-in called CUSTOM that would suit my needs. But how do I give each particle its CUSTOM data at init?

(*Well, mixed success with ArrayMesh. It works but my data gets a bit mangled on the way in. Some built-in’s only take values in ranges 0-1, which is probably obvious to people more familiar with graphics. Additionally there is severe rounding or clipping that I haven’t figured out yet. )