Swicthing to logarithmic z-slicing

Author: vismaychuriwala

src/shaders/clustered_deferred_fullscreen.fs.wgsl

@@ -90,7 +90,7 @@ fn main(in: FragmentInput) -> @location(0) vec4f {
 
   let nearP = camera_uniforms.nearPlane;
   let farP = camera_uniforms.farPlane;
-  let t: f32 = clamp((d - nearP) / (farP - nearP), 0.0, 1.0);
+  let t: f32 = log(d / nearP) / log(farP / nearP);
   let zTile: u32 = u32(clamp(t * f32(Z_SLICES), 0.0, f32(Z_SLICES - 1u)));
 
   let cIdx: u32 = clusterIndex(xTile, yTile, zTile);

src/shaders/clustering.cs.wgsl

@@ -85,10 +85,13 @@ fn compute_cluster_bounds(ix: u32, iy: u32, iz: u32) -> AABB {
   let tanY = camera_uniforms.tanHalfFovY;
   let tanX = camera_uniforms.tanHalfFovX;
 
+  // Logarithmic Z slicing
+  let nearP = camera_uniforms.nearPlane;
+  let farP = camera_uniforms.farPlane;
   let t0 = f32(iz) / f32(Z_SLICES);
   let t1 = f32(iz + 1u) / f32(Z_SLICES);
-  let z_near_d = lerp(camera_uniforms.nearPlane, camera_uniforms.farPlane, t0);
-  let z_far_d  = lerp(camera_uniforms.nearPlane, camera_uniforms.farPlane, t1);
+  let z_near_d = nearP * pow(farP / nearP, t0);
+  let z_far_d  = nearP * pow(farP / nearP, t1);
 
   let z0 = -z_near_d;
   let z1 = -z_far_d;

src/shaders/forward_plus.fs.wgsl

@@ -79,10 +79,10 @@ fn main(in: FragmentInput) -> @location(0) vec4f {
   let yTile = u32(clamp((ny * 0.5 + 0.5) * f32(Y_SLICES),
                         0.0, f32(Y_SLICES - 1u)));
 
-  // Z slice (linear)
+  // Z slice (logarithmic)
   let nearP = camera_uniforms.nearPlane;
   let farP  = camera_uniforms.farPlane;
-  let t = clamp((d - nearP) / (farP - nearP), 0.0, 1.0);
+  let t = log(d / nearP) / log(farP / nearP);
   let zTile = u32(clamp(t * f32(Z_SLICES), 0.0, f32(Z_SLICES - 1u)));
 
   let cIdx = clusterIndex(xTile, yTile, zTile);