1//! A shader showing how to use the vertex position data to output the 
2//! stencil in the right position
3
4// First we import everything we need from bevy_pbr
5// A 2d shader would be vevry similar but import from bevy_sprite instead
6#import bevy_pbr::{
7    mesh_functions,
8    view_transformations::position_world_to_clip
9}
10
11struct Vertex {
12    // This is needed if you are using batching and/or gpu preprocessing
13    // It's a built in so you don't need to define it in the vertex layout
14    @builtin(instance_index) instance_index: u32,
15    // Like we defined for the vertex layout
16    // position is at location 0
17    @location(0) position: vec3<f32>,
18};
19
20// This is the output of the vertex shader and we also use it as the input for the fragment shader
21struct VertexOutput {
22    @builtin(position) clip_position: vec4<f32>,
23    @location(0) world_position: vec4<f32>,
24};
25
26@vertex
27fn vertex(vertex: Vertex) -> VertexOutput {
28    var out: VertexOutput;
29    // This is how bevy computes the world position
30    // The vertex.instance_index is very important. Especially if you are using batching and gpu preprocessing
31    var world_from_local = mesh_functions::get_world_from_local(vertex.instance_index);
32    out.world_position = mesh_functions::mesh_position_local_to_world(world_from_local, vec4(vertex.position, 1.0));
33    out.clip_position = position_world_to_clip(out.world_position.xyz);
34    return out;
35}
36
37@fragment
38fn fragment(in: VertexOutput) -> @location(0) vec4<f32> {
39    // Output a red color to represent the stencil of the mesh
40    return vec4(1.0, 0.0, 0.0, 1.0);
41}