1#define_import_path bevy_pbr::pbr_prepass_functions
2
3#import bevy_pbr::{
4    prepass_io::VertexOutput,
5    prepass_bindings::previous_view_uniforms,
6    mesh_view_bindings::view,
7    pbr_bindings,
8    pbr_types,
9}
10
11// Cutoff used for the premultiplied alpha modes BLEND, ADD, and ALPHA_TO_COVERAGE.
12const PREMULTIPLIED_ALPHA_CUTOFF = 0.05;
13
14// We can use a simplified version of alpha_discard() here since we only need to handle the alpha_cutoff
15fn prepass_alpha_discard(in: VertexOutput) {
16
17#ifdef MAY_DISCARD
18    var output_color: vec4<f32> = pbr_bindings::material.base_color;
19
20#ifdef VERTEX_UVS
21#ifdef STANDARD_MATERIAL_BASE_COLOR_UV_B
22    var uv = in.uv_b;
23#else   // STANDARD_MATERIAL_BASE_COLOR_UV_B
24    var uv = in.uv;
25#endif  // STANDARD_MATERIAL_BASE_COLOR_UV_B
26
27    let uv_transform = pbr_bindings::material.uv_transform;
28    uv = (uv_transform * vec3(uv, 1.0)).xy;
29    if (pbr_bindings::material.flags & pbr_types::STANDARD_MATERIAL_FLAGS_BASE_COLOR_TEXTURE_BIT) != 0u {
30        output_color = output_color * textureSampleBias(pbr_bindings::base_color_texture, pbr_bindings::base_color_sampler, uv, view.mip_bias);
31    }
32#endif // VERTEX_UVS
33
34    let alpha_mode = pbr_bindings::material.flags  & pbr_types::STANDARD_MATERIAL_FLAGS_ALPHA_MODE_RESERVED_BITS;
35    if alpha_mode == pbr_types::STANDARD_MATERIAL_FLAGS_ALPHA_MODE_MASK {
36        if output_color.a < pbr_bindings::material.alpha_cutoff {
37            discard;
38        }
39    } else if (alpha_mode == pbr_types::STANDARD_MATERIAL_FLAGS_ALPHA_MODE_BLEND ||
40            alpha_mode == pbr_types::STANDARD_MATERIAL_FLAGS_ALPHA_MODE_ADD ||
41            alpha_mode == pbr_types::STANDARD_MATERIAL_FLAGS_ALPHA_MODE_ALPHA_TO_COVERAGE) {
42        if output_color.a < PREMULTIPLIED_ALPHA_CUTOFF {
43            discard;
44        }
45    } else if alpha_mode == pbr_types::STANDARD_MATERIAL_FLAGS_ALPHA_MODE_PREMULTIPLIED {
46        if all(output_color < vec4(PREMULTIPLIED_ALPHA_CUTOFF)) {
47            discard;
48        }
49    }
50
51#endif // MAY_DISCARD
52}
53
54#ifdef MOTION_VECTOR_PREPASS
55fn calculate_motion_vector(world_position: vec4<f32>, previous_world_position: vec4<f32>) -> vec2<f32> {
56    let clip_position_t = view.unjittered_clip_from_world * world_position;
57    let clip_position = clip_position_t.xy / clip_position_t.w;
58    let previous_clip_position_t = previous_view_uniforms.clip_from_world * previous_world_position;
59    let previous_clip_position = previous_clip_position_t.xy / previous_clip_position_t.w;
60    // These motion vectors are used as offsets to UV positions and are stored
61    // in the range -1,1 to allow offsetting from the one corner to the
62    // diagonally-opposite corner in UV coordinates, in either direction.
63    // A difference between diagonally-opposite corners of clip space is in the
64    // range -2,2, so this needs to be scaled by 0.5. And the V direction goes
65    // down where clip space y goes up, so y needs to be flipped.
66    return (clip_position - previous_clip_position) * vec2(0.5, -0.5);
67}
68#endif // MOTION_VECTOR_PREPASS