1#import noisy_bevy::fbm_simplex_2d_seeded
2#import bevy_sprite::mesh2d_functions::{
3    get_world_from_local,
4    mesh2d_position_local_to_clip,
5}
6
7struct AsteroidMaterial {
8    params: vec4<f32>
9}
10
11@group(2) @binding(0) var<uniform> material: AsteroidMaterial;
12
13struct Vertex {
14    @builtin(instance_index) instance_index: u32,
15    @location(0) position: vec3<f32>,
16    @location(1) blend_color: vec4<f32>,
17};
18
19struct VertexOutput {
20    @builtin(position) clip_position: vec4<f32>,
21    @location(0) object_position: vec2<f32>,
22};
23
24@vertex
25fn vertex(vertex: Vertex) -> VertexOutput {
26    var out: VertexOutput;
27    // Project the world position of the mesh into screen position
28    let model = get_world_from_local(vertex.instance_index);
29    out.clip_position = mesh2d_position_local_to_clip(model, vec4<f32>(vertex.position, 1.0));
30    out.object_position = vertex.position.xy;
31    return out;
32}
33
34@fragment
35fn fragment(
36    vertex_output: VertexOutput,
37) -> @location(0) vec4<f32> {
38    var p = vertex_output.object_position;
39    let params = material.params;
40    let freq_scale = params.x;
41    let amp_scale = params.y;
42    let radius = params.z;
43    let seed = params.w;
44
45    let r = sqrt(p.x * p.x + p.y * p.y);
46    let d = r - radius;
47
48    // smooth noise same as used on cpu...
49    // let n = simplex_noise_2d(p * freq_scale) * amp_scale;
50
51    // ...or add some extra turbulence to the "atmosphere"
52    let n = fbm_simplex_2d_seeded(p * freq_scale, 7, 2.0, 0.5, seed) * amp_scale;
53
54    var v = d - n;
55    v = pow(-v * 0.1 + 0.3, 2.1);
56
57    return vec4(v, v, v, 1.);
58}