3D array flattening / unflattening to / from compute shader

Question

Hello,

I'm currently using compute shaders to compute 3D arrays of voxels and I'm experiencing some kind of "reversed" 3D coordinate issues, i.e X and Z coordinates seem to be reversed. I am suspecting this is because of the way Unity tranfers a 3D array between the CPU and the GPU using a compute shader.

My question is : how does Unity flattens (and "unflattens") a 3D array when calling ComputeBuffer::GetData() or ComputeBuffer::SetData() ?

When I do this on the CPU, I'm nesting loops in the X, Y, Z order, ie :

             for (int x = 0; x < size; ++x)
             {
                 for (int y = 0; y < size; ++y)
                 {
                     for (int z = 0; z < size; ++z)
                     {
                         flattened3DArray[x + size * (y + size * z)] = actual3DArray[x, y, z];
                     }
                 }
             }

I am suspecting that, internally, Unity is doing that in the Z, Y, X order instead of X, Y, Z, which would explain my issue.

You're gonna say that I just have to try and see by myself. That's true, but I'm still asking the question because I'm wondering whether the behaviour of Unity regarding this is well-defined or if it is some kind of OS or hardware dependent thing, which isn't something I can't check by myself. And also because it's painful to setup. :D

Thanks for your help !

Answer 1

Best Answer

Answer by D43DB33F · Jun 14, 2018 at 03:58 PM

Sorry I didn't search enough before posting :

https://stackoverflow.com/questions/21596373/compute-shaders-input-3d-array-of-floats

That seems to be what I suspected.

Add comment · Share

3D array flattening / unflattening to / from compute shader

1 Reply

Your answer

Follow this Question

Related Questions