Add spatiotemporal dithering to fog

1 files changed, 30 insertions, 3 deletions

diff --git a/fog.cginc b/fog.cginc
index bd1c1da..b1e209c 100644
--- a/fog.cginc
+++ b/fog.cginc
@@ -1,6 +1,7 @@
 #ifndef __FOG_INC
 #define __FOG_INC
 
+#include "audiolink.cginc"
 #include "cnlohr.cginc"
 #include "interpolators.cginc"
 #include "globals.cginc"
@@ -12,8 +13,14 @@ struct FogParams {
     float density;
     float y_cutoff;
     texture2D dithering_noise;
+    float4 dithering_noise_texelsize;
     texture3D density_noise;
     float4 density_noise_scale;
+#if defined(_RAYMARCHED_FOG_HEIGHT_DENSITY)
+    float height_density_min;
+    float height_density_max;
+    float height_density_power;
+#endif
 };
 
 struct FogResult {
@@ -26,7 +33,8 @@ FogResult raymarched_fog(v2f i, FogParams p)
   float3 ro = _WorldSpaceCameraPos;
   float3 rd = normalize(i.eyeVec.xyz);
 
-  ro += rd * 1E-3;
+  const float ro_epsilon = 1E-3;
+  ro += rd * ro_epsilon;
 
   float2 screen_uv = (i.pos.xy + 0.5) / _ScreenParams.xy;
   float zDepthFromMap = SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, screen_uv);
@@ -44,6 +52,15 @@ FogResult raymarched_fog(v2f i, FogParams p)
     }
   }
   linearZ = min(linearZ, distance_to_y);
+  linearZ -= ro_epsilon;
+
+  float dither = p.dithering_noise.SampleLevel(point_repeat_s,
+      screen_uv * _ScreenParams.xy * p.dithering_noise_texelsize.xy, 0).r;
+
+  const float frame = ((float) AudioLinkData(ALPASS_GENERALVU + int2(1, 0)).x);
+  dither = frac(dither + PHI * frame);
+  ro += rd * dither;
+  linearZ -= dither;
 
   float step_size = linearZ / p.steps;
   float3 pp = ro;
@@ -53,15 +70,25 @@ FogResult raymarched_fog(v2f i, FogParams p)
     pp += step_size * rd;
     float cur_d = p.density_noise.SampleLevel(linear_repeat_s,
         pp * p.density_noise_scale.xyz, 0);
+
     cur_d *= p.density * step_size;
 
+#if defined(_RAYMARCHED_FOG_HEIGHT_DENSITY)
+    // Apply height-based density (branchless)
+    float t = saturate((pp.y - p.height_density_min) /
+                      (p.height_density_max - p.height_density_min));
+    float height_factor = pow(1.0 - t, p.height_density_power);
+    cur_d *= height_factor;
+#endif
+
+    cur_d = saturate(cur_d);
     d = d + (1 - d) * cur_d;
   }
 
   FogResult r;
-  r.color.rgb = 1;
+  r.color.rgb = _Raymarched_Fog_Color;
   //r.color.rgb = saturate(log(linearZ) / 5.0);
-  r.color.a = saturate(d);
+  r.color.a = d;
   //r.color.a = 1;
   r.depth = 0.0001;  // Very small depth value to render in front
   return r;