1#import bevy_sprite::{
2    mesh2d_vertex_output::VertexOutput,
3    mesh2d_view_bindings::view,
4}
5
6#ifdef TONEMAP_IN_SHADER
7#import bevy_core_pipeline::tonemapping
8#endif
9
10struct ColorMaterial {
11    color: vec4<f32>,
12    // 'flags' is a bit field indicating various options. u32 is 32 bits so we have up to 32 options.
13    flags: u32,
14    alpha_cutoff: f32,
15};
16
17const COLOR_MATERIAL_FLAGS_TEXTURE_BIT: u32              = 1u;
18const COLOR_MATERIAL_FLAGS_ALPHA_MODE_RESERVED_BITS: u32 = 3221225472u; // (0b11u32 << 30)
19const COLOR_MATERIAL_FLAGS_ALPHA_MODE_OPAQUE: u32        = 0u;          // (0u32 << 30)
20const COLOR_MATERIAL_FLAGS_ALPHA_MODE_MASK: u32          = 1073741824u; // (1u32 << 30)
21const COLOR_MATERIAL_FLAGS_ALPHA_MODE_BLEND: u32         = 2147483648u; // (2u32 << 30)
22
23@group(2) @binding(0) var<uniform> material: ColorMaterial;
24@group(2) @binding(1) var texture: texture_2d<f32>;
25@group(2) @binding(2) var texture_sampler: sampler;
26
27@fragment
28fn fragment(
29    mesh: VertexOutput,
30) -> @location(0) vec4<f32> {
31    var output_color: vec4<f32> = material.color;
32
33#ifdef VERTEX_COLORS
34    output_color = output_color * mesh.color;
35#endif
36
37    if ((material.flags & COLOR_MATERIAL_FLAGS_TEXTURE_BIT) != 0u) {
38        output_color = output_color * textureSample(texture, texture_sampler, mesh.uv);
39    }
40
41    output_color = alpha_discard(material, output_color);
42
43#ifdef TONEMAP_IN_SHADER
44    output_color = tonemapping::tone_mapping(output_color, view.color_grading);
45#endif
46    return output_color;
47}
48
49fn alpha_discard(material: ColorMaterial, output_color: vec4<f32>) -> vec4<f32> {
50    var color = output_color;
51    let alpha_mode = material.flags & COLOR_MATERIAL_FLAGS_ALPHA_MODE_RESERVED_BITS;
52    if alpha_mode == COLOR_MATERIAL_FLAGS_ALPHA_MODE_OPAQUE {
53        // NOTE: If rendering as opaque, alpha should be ignored so set to 1.0
54        color.a = 1.0;
55    }
56#ifdef MAY_DISCARD
57    else if alpha_mode == COLOR_MATERIAL_FLAGS_ALPHA_MODE_MASK {
58       if color.a >= material.alpha_cutoff {
59            // NOTE: If rendering as masked alpha and >= the cutoff, render as fully opaque
60            color.a = 1.0;
61        } else {
62            // NOTE: output_color.a < in.material.alpha_cutoff should not be rendered
63            discard;
64        }
65    }
66#endif // MAY_DISCARD
67
68    return color;
69}