1 files changed, 134 insertions, 0 deletions
diff --git a/wgpu/src/shader/triangle/gradient.wgsl b/wgpu/src/shader/triangle/gradient.wgsl
new file mode 100644
index 00000000..1a8ae3b5
--- /dev/null
+++ b/wgpu/src/shader/triangle/gradient.wgsl
@@ -0,0 +1,134 @@
+struct GradientVertexInput {
+    @location(0) v_pos: vec2<f32>,
+    @location(1) @interpolate(flat) colors_1: vec4<u32>,
+    @location(2) @interpolate(flat) colors_2: vec4<u32>,
+    @location(3) @interpolate(flat) colors_3: vec4<u32>,
+    @location(4) @interpolate(flat) colors_4: vec4<u32>,
+    @location(5) @interpolate(flat) offsets: vec4<u32>,
+    @location(6) direction: vec4<f32>,
+}
+
+struct GradientVertexOutput {
+    @builtin(position) position: vec4<f32>,
+    @location(0) raw_position: vec2<f32>,
+    @location(1) @interpolate(flat) colors_1: vec4<u32>,
+    @location(2) @interpolate(flat) colors_2: vec4<u32>,
+    @location(3) @interpolate(flat) colors_3: vec4<u32>,
+    @location(4) @interpolate(flat) colors_4: vec4<u32>,
+    @location(5) @interpolate(flat) offsets: vec4<u32>,
+    @location(6) direction: vec4<f32>,
+}
+
+@vertex
+fn gradient_vs_main(input: GradientVertexInput) -> GradientVertexOutput {
+    var output: GradientVertexOutput;
+
+    output.position = globals.transform * vec4<f32>(input.v_pos, 0.0, 1.0);
+    output.raw_position = input.v_pos;
+    output.colors_1 = input.colors_1;
+    output.colors_2 = input.colors_2;
+    output.colors_3 = input.colors_3;
+    output.colors_4 = input.colors_4;
+    output.offsets = input.offsets;
+    output.direction = input.direction;
+
+    return output;
+}
+
+/// Returns the current interpolated color with a max 8-stop gradient
+fn gradient(
+    raw_position: vec2<f32>,
+    direction: vec4<f32>,
+    colors: array<vec4<f32>, 8>,
+    offsets: array<f32, 8>,
+    last_index: i32
+) -> vec4<f32> {
+    let start = direction.xy;
+    let end = direction.zw;
+
+    let v1 = end - start;
+    let v2 = raw_position - start;
+    let unit = normalize(v1);
+    let coord_offset = dot(unit, v2) / length(v1);
+
+    //need to store these as a var to use dynamic indexing in a loop
+    //this is already added to wgsl spec but not in wgpu yet
+    var colors_arr = colors;
+    var offsets_arr = offsets;
+
+    var color: vec4<f32>;
+
+    let noise_granularity: f32 = 0.3/255.0;
+
+    for (var i: i32 = 0; i < last_index; i++) {
+        let curr_offset = offsets_arr[i];
+        let next_offset = offsets_arr[i+1];
+
+        if (coord_offset <= offsets_arr[0]) {
+            color = colors_arr[0];
+        }
+
+        if (curr_offset <= coord_offset && coord_offset <= next_offset) {
+            let from_ = colors_arr[i];
+            let to_ = colors_arr[i+1];
+            let factor = smoothstep(curr_offset, next_offset, coord_offset);
+
+            color = interpolate_color(from_, to_, factor);
+        }
+
+        if (coord_offset >= offsets_arr[last_index]) {
+            color = colors_arr[last_index];
+        }
+    }
+
+    return color + mix(-noise_granularity, noise_granularity, random(raw_position));
+}
+
+@fragment
+fn gradient_fs_main(input: GradientVertexOutput) -> @location(0) vec4<f32> {
+    let colors = array<vec4<f32>, 8>(
+        unpack_u32(input.colors_1.xy),
+        unpack_u32(input.colors_1.zw),
+        unpack_u32(input.colors_2.xy),
+        unpack_u32(input.colors_2.zw),
+        unpack_u32(input.colors_3.xy),
+        unpack_u32(input.colors_3.zw),
+        unpack_u32(input.colors_4.xy),
+        unpack_u32(input.colors_4.zw),
+    );
+
+    let offsets_1: vec4<f32> = unpack_u32(input.offsets.xy);
+    let offsets_2: vec4<f32> = unpack_u32(input.offsets.zw);
+
+    var offsets = array<f32, 8>(
+        offsets_1.x,
+        offsets_1.y,
+        offsets_1.z,
+        offsets_1.w,
+        offsets_2.x,
+        offsets_2.y,
+        offsets_2.z,
+        offsets_2.w,
+    );
+
+    var last_index = 7;
+    for (var i: i32 = 0; i <= 7; i++) {
+        if (offsets[i] >= 1.0) {
+            last_index = i;
+            break;
+        }
+    }
+
+    return gradient(input.raw_position, input.direction, colors, offsets, last_index);
+}
+
+fn unpack_u32(color: vec2<u32>) -> vec4<f32> {
+    let rg: vec2<f32> = unpack2x16float(color.x);
+    let ba: vec2<f32> = unpack2x16float(color.y);
+
+    return vec4<f32>(rg.y, rg.x, ba.y, ba.x);
+}
+
+fn random(coords: vec2<f32>) -> f32 {
+    return fract(sin(dot(coords, vec2(12.9898,78.233))) * 43758.5453);
+}