Metal 4 & Acceleration Structures

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Created 1w

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I have really enjoyed looking through the code and videos related to Metal 4. Currently, my interest is to update a ReSTIR Project and take advantage of more robust ways to refit acceleration Structures and more powerful ways to access resources.

I am working in Swift and have encountered a couple of puzzles:

What is the 'accepted' way to create a MTL4BufferRange to store indices and vertices?

How do I properly rewrite Swift code to build and compact an Acceleration Structure?

I do realize that this is all in Beta and will happily look through Code Samples this Fall. If other guidance is available earlier, that would be fabulous!

Thank you

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Answer 1

DTS Engineer OP

Apple

1w

Hello,

That makes at least two of us who really enjoyed the Metal 4 sessions. :)

Give us some time to determine answers for your questions about Swift and Metal. Documentation is expected to be available in both Obj-C and Swift so that's a start.

Please clarify "How do I properly rewrite Swift code to build and compact an Acceleration Structure?"

Are you asking how to use copyAndCompact(sourceAccelerationStructure:destinationAccelerationStructure:) or how would write your own equivalent in Swift (for use with ReSTIR)?

Re: sample code, it looks like we're continuing to publish samples primarily in Obj-C. Please let us know if you'd like more samples written with Swift by sending us an enhancement request using the Feedback Assistant.

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Answer 2

John Lobe OP

1w

Thanks for your reply.

My first issue came up when trying to use a MTL4ComputeCommandEncoder to build an AccelerationStructure:

func build(destinationAccelerationStructure: any MTLAccelerationStructure, descriptor: MTL4AccelerationStructureDescriptor, scratchBuffer: MTL4BufferRange)

The setup of the scratch buffer ( MTL4BufferRangeMake(::) ) is unfamiliar to me although I have looked through the documentation

I am accustomed to using the MTLDevice and Acceleration Structure Sizes to build an old-school scratch buffer. Any naive attempts to use the gpuAddress value from such an existing MTLBuffer have predictably failed with the message:

__buildAccelerationStructure:descriptor:scratchBuffer:]:2450: failed assertion `Compute Command Encoder Build Acceleration Structure Validation Metal 4 does not support raytracing with software emulation __

So, I guess my initial question is how do I properly create a MTL4BufferRange to use in the build function?

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