Add soft shadows

README.md

@@ -18,6 +18,8 @@ Controls:
 - PBS
 - glTF models
 - 1 realtime pointlight
+- Shadow mapping
+- Soft shadows
 - Simple wgsl preprocessor for includes
 - Runs on WASM and native desktop
   - Tested on:
@@ -27,7 +29,6 @@ Controls:
     - `Chrome 109.0.5414.120`
 
 TODO:
-- Shadow mapping
 - Transparency
 - Restructuring
     - Simplify/abstract renderpasses; will be nice to have for PP and GI

res/shaders/constants.wgsl

@@ -1,3 +1,6 @@
 const PI = 3.14159;
 const INV_SQRT_2 = 0.70710678118654752440; // 1 / sqrt(2)
 const INV_SQRT_3 = 0.57735026918962576451; // 1 / sqrt(3)
+const SHADOW_SAMPLES = 8;
+const INV_SHADOW_SAMPLES = 1.0 / 8.0;
+const SHADOW_SAMPLE_DIST = 0.001;

res/shaders/pbr.wgsl

@@ -74,14 +74,29 @@ fn sample_direct_light(index: i32, light_coords: vec4<f32>) -> f32 {
     let flip_correction = vec2<f32>(0.5, -0.5);
     let proj_correction = 1.0 / light_coords.w;
     let light_local = light_coords.xy * flip_correction * proj_correction + vec2<f32>(0.5, 0.5);
+    let reference_depth = light_coords.z * proj_correction;
 
-    return textureSampleCompareLevel(
+    var total_sample = 0.0;
+    for (var i: i32 = 0; i < SHADOW_SAMPLES; i++) {
+        let phase = i % 4;
+        var offset = vec2<f32>(f32(i / 4) * SHADOW_SAMPLE_DIST);
+        if (phase == 1 || phase == 3) {
+            offset.x = -offset.x;
+        }
+        if (phase == 2 || phase == 3) {
+            offset.y = -offset.y;
+        }
+        let s = textureSampleCompareLevel(
              t_light_depth,
              s_light_depth,
-        light_local,
+             light_local + offset,
              index,
-        light_coords.z * proj_correction
+             reference_depth
          );
+        total_sample += s * INV_SHADOW_SAMPLES;
+    }
+
+    return total_sample;
 }
 
 @fragment
@@ -118,6 +133,8 @@ fn fs_main(vert: VertexOutput) -> @location(0) vec4<f32> {
         }
 
         in_light = sample_direct_light(i, light_coords);
+        // TODO should break even if 0 since we're inside frustum.
+        // See if causes issues with bias overlap between directions.
         if (in_light > 0.0) {
             break;
         }
@@ -138,7 +155,7 @@ fn fs_main(vert: VertexOutput) -> @location(0) vec4<f32> {
 
         // radiance
         let radiance_strength = max(dot(normal_dir, light_dir), 0.0);
-        let radiance = radiance_strength * light.color.xyz * light.color.w * light_attenuation;
+        let radiance = radiance_strength * light.color.xyz * light.color.w * light_attenuation * in_light;
 
         // brdf shading
         total_radiance += radiance * brdf(