Using bindgroup other than 0

[rYuuk]

I am not sure, how to use bind group other than 0 for my compute shader. Is this functionality available?

@group(1) @binding(0)
var<uniform> value: i32;

It seems that by default it goes to 0

let bind_group_layout = pipeline.get_bind_group_layout(0);
      ...
          cpass.set_pipeline(pipeline);
          cpass.set_bind_group(0, &bind_group, &[]);
          cpass.dispatch_workgroups(
              compute_pass.workgroups[0],
              compute_pass.workgroups[1],
              compute_pass.workgroups[2],
          )
      }

[tombh]

Is it possible that you're confusing bind_group and bind_group_layout? A bind_group_layout doesn't actually contain any data. It's Rust's bind_group[0] that maps to WGSL's @binding(0).

So if we look at the example in the README:

let worker = AppComputeWorkerBuilder::new(world)
    // Add a uniform variable
    .add_uniform("uni", &5.)

    // Add a staging buffer, it will be available from
    // both CPU and GPU land.
    .add_staging("values", &[1., 2., 3., 4.])

    // Create a compute pass from your compute shader
    // and define used variables
    .add_pass::<SimpleShader>([4, 1, 1], &["uni", "values"])
    .build();

Then add_uniform("uni", &5.) maps to:

@group(0) @binding(0)
var<uniform> uni: f32;

And .add_staging("values", &[1., 2., 3., 4.]) maps to:

@group(0) @binding(1)
var<storage, read_write> my_storage: array<f32>;

[rYuuk]

Sorry if it wasn't clear, I meant the @group(0) in wgsl shader and not the binding

@group(0) @binding(0)
var<uniform> uni: f32;

@group(1) @binding(0)
var<storage, read_write> my_storage: array<f32>;

[tombh]

Ahh yes, I see what you mean. I must say I've never actually used a group, and have to admit I'm not sure what it's for. But anyway, it's set in the first arg here: cpass.set_bind_group(0, &bind_group, &[]); right?

[AnthonyTornetta]

@rYuuk What use-case are you trying to solve by not using the default group 0 in your compute shader?

[rYuuk]

@rYuuk What use-case are you trying to solve by not using the default group 0 in your compute shader?

I had a compute shader which calculate height change for vertex, following is small example. So instead using binding index which going till 10 for me I wanted to just change the group to 1 to make it easier manage.

#import "shaders/crater.wgsl"::calculateCraterDepth

@group(0) @binding(0)
var<storage, read> vertices: array<vec3<f32>>;
 
@group(0) @binding(1)
var<storage, read_write> heights: array<f32>;

@compute @workgroup_size(1024)
fn main(@builtin(global_invocation_id) id: vec3<u32>) {
     let index = id.x;
 
     if (index >= num_vertices) {
         return;
     }
     // some other stuff here ... 
     let craterDepth = calculateCraterDepth(vertexPos);
     let finalHeight = 1 + craterDepth + noiseSum;
     heights[index] = finalHeight;
}

@group(1) @binding(0)
var<uniform> num_craters: u32;

@group(1) @binding(1)
var<uniform> rim_steepness: f32;

fn calculateCraterDepth(vertexPos: vec3<f32>) -> f32 {
    var craterHeight: f32 = 0.0;
    
    // some calculation here
    
    retrun craterHeight;
}

[AnthonyTornetta]

Ah I understand your usecase. I'm pretty busy right now, so I won't be able to work on this within short order. If you want to make a PR implementing this, I would be happy to review it and merge it in. If you do make a PR, try to avoid creating any breaking changes with the current API.