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3D [Metal] vertex_id value when using indirectBuffer

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What is the value of the vertex_id attribute in a metal shader when using drawPrimitives with indirectBuffer?

I know it is relative to baseVertex when using normal draw but how does it work with indirect draw arguments?

It doesn't say anything in the spec so any info on this would really help.

Thank you.

Edited by mark_braga

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It is the same, it starts at zero.


At the metal level, if you look for ISA in PIX (if using DX12 and AMD), you would see that the shader receive the offset in a scalar register and the vid is just auto generated value, and it sums them prior to fetching the buffer values. Something nice on Consoles, we can so know both 0 based and absolute. On PC, we only have the later :(



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