WIP

src/pipelines/eraser/eraser-texture.wgsl

@@ -0,0 +1,53 @@
+struct Settings {
+  eraserRadius: f32,
+  eraserRadiusSquared: f32,
+  padding1: f32,
+  padding2: f32,
+};
+
+@group(1) @binding(0) var<uniform> settings: Settings;
+
+struct VertexOutput {
+  @builtin(position) position: vec4<f32>,
+  @location(0) screenPosition: vec2<f32>,
+  @location(1) start: vec2<f32>,
+  @location(2) end: vec2<f32>
+}
+
+@vertex
+fn vertex(
+  @location(0) screenPosition: vec2<f32>,
+  @location(1) @interpolate(flat) start: vec2<f32>,
+  @location(2) @interpolate(flat) end: vec2<f32>
+) -> VertexOutput {
+  let uv = screenPosition / state.size;
+  let position = vec2(uv.x * 2.0 - 1.0, 1.0 - uv.y * 2.0);
+  return VertexOutput(vec4(position, 0.0, 1.0), screenPosition, start, end);
+}
+
+@fragment
+fn fragment(
+  @location(0) screenPosition: vec2<f32>,
+  @location(1) start: vec2<f32>,
+  @location(2) end: vec2<f32>
+) -> @location(0) vec4<f32> {
+  if distanceSquaredFromLine(screenPosition, start, end) > settings.eraserRadiusSquared {
+    discard;
+  }
+
+  return vec4<f32>(0.0, 0.0, 0.0, 0.0);
+}
+
+fn distanceSquaredFromLine(position: vec2<f32>, start: vec2<f32>, end: vec2<f32>) -> f32 {
+  let pa = position - start;
+  let direction = end - start;
+  let denominator = dot(direction, direction);
+
+  if denominator <= 0.0001 {
+    return dot(pa, pa);
+  }
+
+  let q = clamp(dot(pa, direction) / denominator, 0.0, 1.0);
+  let nearestOffset = pa - direction * q;
+  return dot(nearestOffset, nearestOffset);
+}