How to make a &mut Image2d

[Boris-rnd]

I tried:

#[spirv(storage_buffer, descriptor_set = 1, binding = 0)] output: &mut Image2d, // Image2D is a Image!(2D, sampled=false, ...)

But it doesn't work because &mut Image2d is a "UniformConstant" so you can't make mutables.
I've tried reading through the source code but I don't find how to fix this

[Firestar99]

You don't need Images to be mutable to write to them, Image2D::write(&self, ...) takes self by plain reference.

Yes buffers do require &mut, and buffers are in the wrong here, cause &mut also implies exclusive access, which is obviously not the case since the &mut is shared with all the threads. This is one of the biggest design issues of current rust-gpu.

[Firestar99]

writeonly images is something only wgpu needs. And I can't remember how it was exposed, if it was exposed at all. So you may just have to tell wgpu it's a read-write image instead of writeonly. @schell probably knows how this is exposed, if we ever exposed it at all?

[Boris-rnd]

Yeah but I was using rgba16f which doesn't support read write on wgpu
I will fork my engine and try to change that...

[schell]

I dug into something similar to this but I don't remember what or how.

[Firestar99]

I wonder if we never fixed that corner and you settled for read-write textures?

[schell]

I think when I was doing that, I was trying to write to depth textures to use as a hierarchical z-buffer and it was a nightmare. I ended up using storage buffers and my own data type instead.