DoF: Tweaked the prefilter/postfilter to reduce artifacts.

Tweaked the prefilter and postfilter to hide unblurred areas that
usually appear on boundaries between focused and unfocused objects. This
could be one of the supposed solutions for issue #40 (DoF doesn't handle
alpha cutout very well) but possibly adds noticeable dark seams.

Author: keijiro

PostProcessing/Resources/Shaders/Common.cginc

@@ -58,6 +58,12 @@ inline half Min3(half x, half y, half z) { return min(x, min(y, z)); }
 inline half Max3(half3 x) { return max(x.x, max(x.y, x.z)); }
 inline half Max3(half x, half y, half z) { return max(x, max(y, z)); }
 
+inline half Min4(half4 x) { return min(x.x, min(x.y, min(x.z, x.w))); }
+inline half Min4(half x, half y, half z, half w) { return min(x, min(y, min(z, w))); }
+
+inline half Max4(half4 x) { return max(x.x, max(x.y, max(x.z, x.w))); }
+inline half Max4(half x, half y, half z, half w) { return max(x, max(y, min(z, w))); }
+
 inline half  Pow2(half  x) { return x * x; }
 inline half2 Pow2(half2 x) { return x * x; }
 inline half3 Pow2(half3 x) { return x * x; }

PostProcessing/Resources/Shaders/DepthOfField.cginc

@@ -87,7 +87,9 @@ half4 FragPrefilter(VaryingsDOF i) : SV_Target
     avg /= dot(weights, 1.0);
 
     // Output CoC = average of CoCs
-    half coc = dot(cocs, 0.25);
+    half cocmin = Min4(cocs);
+    half cocmax = Max4(cocs);
+    half coc = -cocmin > cocmax ? cocmin : cocmax;
 
     // Premultiply CoC again.
     avg *= smoothstep(0, _MainTex_TexelSize.y * 2, abs(coc));
@@ -187,21 +189,35 @@ half4 FragPostBlur(VaryingsDOF i) : SV_Target
 {
     // 9-tap tent filter
     float4 duv = _MainTex_TexelSize.xyxy * float4(1, 1, -1, 0);
-    half4 acc;
 
-    acc  = tex2D(_MainTex, i.uv - duv.xy);
-    acc += tex2D(_MainTex, i.uv - duv.wy) * 2;
-    acc += tex2D(_MainTex, i.uv - duv.zy);
+    half4 c0 = tex2D(_MainTex, i.uv - duv.xy);
+    half4 c1 = tex2D(_MainTex, i.uv - duv.wy);
+    half4 c2 = tex2D(_MainTex, i.uv - duv.zy);
 
-    acc += tex2D(_MainTex, i.uv + duv.zw) * 2;
-    acc += tex2D(_MainTex, i.uv         ) * 4;
-    acc += tex2D(_MainTex, i.uv + duv.xw) * 2;
+    half4 c3 = tex2D(_MainTex, i.uv + duv.zw);
+    half4 c4 = tex2D(_MainTex, i.uv         );
+    half4 c5 = tex2D(_MainTex, i.uv + duv.xw);
 
-    acc += tex2D(_MainTex, i.uv + duv.zy);
-    acc += tex2D(_MainTex, i.uv + duv.wy) * 2;
-    acc += tex2D(_MainTex, i.uv + duv.xy);
+    half4 c6 = tex2D(_MainTex, i.uv + duv.zy);
+    half4 c7 = tex2D(_MainTex, i.uv + duv.wy);
+    half4 c8 = tex2D(_MainTex, i.uv + duv.xy);
 
-    return acc / 16;
+    half4 acc = c0 * 1 + c1 * 2 + c2 * 1 +
+                c3 * 2 + c4 * 4 + c5 * 2 +
+                c6 * 1 + c7 * 2 + c8 * 1;
+
+    half aa =
+        c0.a * c0.a * 1 + c1.a * c1.a * 2 + c2.a * c2.a * 1 +
+        c3.a * c3.a * 2 + c4.a * c4.a * 4 + c5.a * c5.a * 2 +
+        c6.a * c6.a * 1 + c7.a * c7.a * 2 + c8.a * c8.a * 1;
+
+    half wb = 1.2;
+    half a = (wb * acc.a - aa) / (wb * 16 - acc.a);
+
+    acc /= 16;
+
+    half3 rgb = acc.rgb * (1 + saturate(acc.a - a));
+    return half4(rgb, a);
 }
 
 #endif // __DEPTH_OF_FIELD__