How do you clear a GPU texture using metal?

Question

I've got a 3D texture that is only accessible to the GPU, which I'm trying to clear at the start of a frame. I've tried setting each element to zero using a computer shader, but that's taking nearly 3ms for a 64x64x64 texture, and I'd like to use something bigger than that.

It would be great if I could do something like the clear-on-load action for color attachments, but I'm don't think that's possible in this situation.

What's the fastest way to clear the texture?

Answer 1

The easiest way to do this is by using the renderPassDesciptor's loadActions, like so:

MTLRenderPassDescriptor *rpdesc = [MTLRenderPassDescriptor renderPassDescriptor];
rpdesc.colorAttachments[0].clearColor = MTLClearColorMake(0,0,0,0);
rpdesc.colorAttachments[0].loadAction = MTLLoadActionClear;