Fix shadowmap sampling outside of frustum

res/shaders/constants.wgsl

@@ -1 +1,3 @@
-const PI = 3.14159;
+const PI = 3.14159;
+const INV_SQRT_2 = 0.70710678118654752440; // 1 / sqrt(2)
+const INV_SQRT_3 = 0.57735026918962576451; // 1 / sqrt(3)

res/shaders/pbr.wgsl

@@ -125,8 +125,24 @@ fn fs_main(vert: VertexOutput) -> @location(0) vec4<f32> {
     var total_radiance: vec3<f32>;
 
     var in_light = 0.0;
-    for (var i: i32 = 0; i < 1; i++) {
+    for (var i: i32 = 0; i < 6; i++) {
-        in_light = sample_direct_light(i, light.matrices[i] * vert.world_position);
+        let light_coords = light.matrices[i] * vert.world_position;
+
+        let light_dir = normalize(light_coords.xyz);
+        let bias = 0.005;
+        // z can never be smaller than this inside 90 degree frustum
+        if (light_dir.z < INV_SQRT_3 - bias) {
+            continue;
+        }
+        // x and y can never be larger than this inside frustum
+        if (abs(light_dir.y) > INV_SQRT_2 + bias) {
+            continue;
+        }
+        if (abs(light_dir.x) > INV_SQRT_2 + bias) {
+            continue;
+        }
+
+        in_light = sample_direct_light(i, light_coords);
         if (in_light > 0.0) {
             break;
         }