50 lines
1.8 KiB
WebGPU Shading Language
50 lines
1.8 KiB
WebGPU Shading Language
// NOTE: The `common.wgsl` source is prepended to this before compilation.
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struct VertexOutput {
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@builtin(position) position: vec4<f32>,
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@location(0) uv: vec2<f32>,
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};
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@group(1) @binding(0) var<uniform> transforms: common__Transforms;
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@group(2) @binding(0) var parent_texture: texture_2d<f32>;
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@group(2) @binding(1) var current_texture: texture_2d<f32>;
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@group(2) @binding(2) var texture_sampler: sampler;
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@vertex
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fn main_vertex(in: common__VertexInput) -> VertexOutput {
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let pos = common__globals.view_matrix * transforms.world_matrix * vec4<f32>(in.position.x, in.position.y, 1.0, 1.0);
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let uv = vec2<f32>((pos.x + 1.0) / 2.0, -((pos.y - 1.0) / 2.0));
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return VertexOutput(pos, uv);
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}
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fn blend_func(src: vec3<f32>, dst: vec3<f32>) -> vec3<f32> {
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return src * dst;
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}
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@fragment
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fn main_fragment(in: VertexOutput) -> @location(0) vec4<f32> {
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// dst is the parent pixel we're blending onto
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var dst: vec4<f32> = textureSample(parent_texture, texture_sampler, in.uv);
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// src is the pixel that we want to apply
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var src: vec4<f32> = textureSample(current_texture, texture_sampler, in.uv);
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// Flash does the following, which makes this not a pure multiply:
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// If src.a is 0, don't write anything
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// If dst.a is 0, replace the pixel entirely
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// Else, blend
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if (src.a > 0.0) {
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if (dst.a > 0.0) {
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return vec4<f32>(src.rgb * (1.0 - dst.a) + dst.rgb * (1.0 - src.a) + src.a * dst.a * blend_func(src.rgb / src.a, dst.rgb / dst.a), src.a + dst.a * (1.0 - src.a));
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} else {
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return src;
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}
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} else {
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if (true) {
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// This needs to be in a branch because... reasons. Bug in naga.
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// https://github.com/gfx-rs/naga/issues/2168
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discard;
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}
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return dst;
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}
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}
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