A question about [[vertex_id]]

[zhrit]

In voxelization.metal, vid [[ vertex_id ]] is used to get face id (via vid / 3).
I have a question about the range of the 'vid.
For example, if the vertex count is 4, and the indices count is 12, then what the range of vid ? [0-3] or [0-11]?
If the range of vid is [0-3], face_id=vid/3 would be wrong.
I have tried on OpenGL, the range of vid is [0-3] actually, so how about Metal?

[kakashidinho]

[[vertex_id]] would return the index value from index buffer if you use drawElements style similar to GL.
But in this demo, I don't use drawElements , I use drawArrays and read the index buffer directly inside vertex shader myself.
So in my case with drawArrays(100), [[vertex_id]] would refer to an id from [0-99]

[zhrit]

I see, thanks for your reply.