Merge pull request #1882 from nicksenger/shadows

Quad shadows

1 files changed, 7 insertions, 11 deletions

diff --git a/wgpu/src/shader/quad.wgsl b/wgpu/src/shader/quad.wgsl
index f919cfe2..4de73362 100644
--- a/wgpu/src/shader/quad.wgsl
+++ b/wgpu/src/shader/quad.wgsl
@@ -11,19 +11,15 @@ fn distance_alg(
     size: vec2<f32>,
     radius: f32
 ) -> f32 {
-    var inner_size: vec2<f32> = size - vec2<f32>(radius, radius) * 2.0;
+    var inner_half_size: vec2<f32> = (size - vec2<f32>(radius, radius) * 2.0) / 2.0;
     var top_left: vec2<f32> = position + vec2<f32>(radius, radius);
-    var bottom_right: vec2<f32> = top_left + inner_size;
-
-    var top_left_distance: vec2<f32> = top_left - frag_coord;
-    var bottom_right_distance: vec2<f32> = frag_coord - bottom_right;
-
-    var dist: vec2<f32> = vec2<f32>(
-        max(max(top_left_distance.x, bottom_right_distance.x), 0.0),
-        max(max(top_left_distance.y, bottom_right_distance.y), 0.0)
-    );
+    return rounded_box_sdf(frag_coord - top_left - inner_half_size, inner_half_size, 0.0);
+}
 
-    return sqrt(dist.x * dist.x + dist.y * dist.y);
+// Given a vector from a point to the center of a rounded rectangle of the given `size` and
+// border `radius`, determines the point's distance from the nearest edge of the rounded rectangle
+fn rounded_box_sdf(to_center: vec2<f32>, size: vec2<f32>, radius: f32) -> f32 {
+    return length(max(abs(to_center) - size + vec2<f32>(radius, radius), vec2<f32>(0.0, 0.0))) - radius;
 }
 
 // Based on the fragement position and the center of the quad, select one of the 4 radi.