Chromium Experimental Dynamic Binding

The chromium_experimental_dynamic_binding is an experimental extension that provides different prototype options to support the WebGPU bindless prototypes.

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

resource_binding

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));
    }
}