Chromium Experimental Dynamic Binding

The chromium_experimental_dynamic_binding is an experimental extension that allows using a new resource_binding type. This provides the needed basis for dynamic binding (a.k.a. bind-less).

Status

This extension is experimental and the syntax is being discussed. No official WebGPU specification has been written yet.

Availability

| Platform | Notes | | SPIR-V | Requires SPV_EXT_descriptor_indexing extension and RuntimeDescriptorArray capability | | HLSL | Supported for DXC, not FXC | | MSL | Supported (TODO determine if there are Metal version restrictions) | | GLSL | Not supported |

Due to limited availability, this will need an enable statement to be used. For this experimental extension it would be enable chromium_experimental_dynamic_binding.

Specification

resource_binding

  • A new resource_binding type is added

  • A resource_binding cannot be passed as a function parameter. This is because there is no way in WGSL to currently write the needed pointer type (e.g. ptr<handle, resource_binding, write>).

  • A resource_binding can not be accessed with the usual array subscript operators. e.g. the following is disallowed:

    var a: resource_binding;
fn foo() {
    var b = a[0];
}

  • Two helper methods getBinding and hasBinding are provided for accessing a resource_binding.

hasBinding

@must_use fn hasBinding<T>(a: resource_binding, index: I) -> bool
  • I is an i32 or u32
  • T is a format-less storage texture (e.g. texture_storage_2d<f32>), sampled texture, multisampled texture, or depth texture.

hasBinding returns true if the item a index of the array is of type T.

getBinding

@must_use fn getBinding<T>(a: resource_binding, index: I) -> T
  • I is an i32 or u32
  • T is a format-less storage texture (e.g. texture_storage_2d<f32>), sampled texture, multisampled texture, or depth texture.

getBinding returns the value at index of type T.

If index is outside the bounds of the binding array then a default texture of type T will be returned. If the item at index is not of type T then a default texture of type T is returned.

arrayLength

@must_use fn arrayLength(a: resource_binding) -> u32

Returns the length of the array.

Example usage

enable chromium_experimental_dynamic_binding;

@group(0) @binding(0) var textures : resource_binding;

@fragment fn fs() {
    if (hasBinding<texture_2d<f32>>(textures, 0)) {
        let tex = textureLoad(getBinding<texture_2d<f32>>(textures, 0));
    }
}