unhelpful error in array use

[pro465]

im a beginner in wgpu, so apologies if i should have posted this the wgpu repo

so, i was creating a mandelbrot viewer but got stopped by this error:

[2023-05-06T13:29:50Z ERROR wgpu::backend::direct] Handling wgpu errors as fatal by default
thread 'main' panicked at 'wgpu error: Validation Error

Caused by:
    In Device::create_shader_module
      note: label = `shader.wgsl`

Shader validation error:
   ┌─ shader.wgsl:9:1
   │
 9 │ ╭ struct VertexOutput {
10 │ │     @builtin(position) clip_position: vec4<f32>,
11 │ │     @location(2) @interpolate(flat) zn: array<vec2<f32>, 1000u>,
12 │ │     @location(0) delta: vec2<f32>,
   │ ╰─────────────────────────────────^ naga::Type [6]


    Entry point vs_main at Vertex is invalid
    The type [5] cannot be used for user-defined entry point inputs or outputs

', [..]

the shader code:

// Vertex shader

struct VertexInput {
    @location(0) position: vec3<f32>,
    @location(1) actual: vec3<f32>,

};

struct VertexOutput {
    @builtin(position) clip_position: vec4<f32>,
    @location(2) @interpolate(flat) zn: array<vec2<f32>, 1000u>,
    @location(0) delta: vec2<f32>,
};

@vertex
fn vs_main(
    model: VertexInput,
) -> VertexOutput {
    var out: VertexOutput;
    out.delta = model.actual.xy * model.position.z;
    out.clip_position = vec4(model.actual, 1.0);
    var i = 0u;
    var z = vec2(0.0);
    let c = model.position.xy;

    while i < 1000u {
        out.zn[i] = z;
        i += 1u;
        z = vec2(z.x*z.x-z.y*z.y, 2.0*z.x*z.y)+c;
    }
    return out;
}

// Fragment shader

@fragment
fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
    let m = in.zn[999];
    return vec4(m,m,m,1.0);
}

fn mandel(m: vec2<f32>) -> f32 {
    let max_iter: u32 = 1000u;
    var iter: u32 = 0u;
    var z = vec2<f32>(0.0);

    while iter < max_iter {
        let r = z.x*z.x - z.y*z.y + m.x;
        let i = 2.0*z.x*z.y + m.y;

        if r*r + i*i > 4.0 {
            break;
        }
        z = vec2(r, i);
        iter = iter + 1u;
    }

    return f32(iter)/f32(max_iter);
}

i could not even understand what it means, let alone fix it :<

[cwfitzgerald]

The issue is that you can't pass arrays (or matrixes) in/out of a shader as vertex attributes. Additionally, even if this is valid, you generally only have 64 or so vertex attributes.

[pro465]

so, how do i fix it? i've heard of var<private> but don't know what it means...

[pro465]

also, is this only a naga issue or is it a rule by webgpu?