Can WGSL share some logic with Rust

[songhuaixu]

Can WGSL share some logic with Rust

[kpreid]

Unfortunately, there are not currently any tools (that I am aware of) which will do that on a straightforward basis. rust-gpu is notable in this space, but quite heavyweight (it's an entire new backend for the Rust compiler).

However, Rust and WGSL do have a common subset of syntax, so you could share some code simply as text, with some setup. For example,

fn luminance(linear_rgb: vec3f) -> f32 {
    return dot(linear_rgb, vec3f(0.2126, 0.7152, 0.0722));
}

is syntactically valid as both WGSL and Rust, so if you accompany it with suitable Rust item declarations, it will run. You'd use include_str!("shared.wgsl") as usual to load it as a shader, then to load it as Rust, use include! in a module that defines appropriate items to mimic WGSL builtins:

mod from_shader {
    type vec3f = [f32; 3]; // or your choice of vector library type
    fn vec3f(a: f32, b: f32, c: f32) -> vec3f { [a, b, c] }
    fn dot(a: vec3f, b: vec3f) -> f32 { 
        a[0] * b[0] + a[1] * b[1] + a[2] * b[2]
    }
    
    include!("shared.wgsl");

    // write `pub fn`s that use the included fns here
}

The most annoying part of this will be that pub fn isn't valid WGSL, so you'll have to write wrapper functions to make them visible outside the module.