Made shadows blurry (thru implementing variance mapping)

src/core/SkShadowShader.cpp

Index: src/core/SkShadowShader.cpp
diff --git a/src/core/SkShadowShader.cpp b/src/core/SkShadowShader.cpp
index 5fc992acc14dd790ab86e43e6a761ecc7b7db8bc..cbe218ba62bd23b141b61ee55d788e054fb962f9 100644
--- a/src/core/SkShadowShader.cpp
+++ b/src/core/SkShadowShader.cpp
@@ -250,21 +250,21 @@ public:
                                          scaleVec.c_str(),
                                          widthUniName, heightUniName,
                                          depthMapWidthUniName[i], depthMapHeightUniName[i]);

[robertphillips, 2016/08/10 14:23:18]

??

[vjiaoblack, 2016/08/11 18:28:51]

Done.

-
+//
                 fragBuilder->codeAppendf("vec2 %s = 1 - %s;\n",
                                          scaleOffsetVec.c_str(), scaleVec.c_str());
 
-
                 fragBuilder->codeAppendf("vec2 %s = (vMatrixCoord_0_1_Stage0 + "
-                                                    "vec2(%s.x, 0 - %s.y)) "
-                                                   " * %s + vec2(0,1) * %s;\n",
-
+                                                 "vec2(%s.x, 0 - %s.y)) "
+                                                 " * %s + vec2(0,1) * %s;\n",
                                          povCoord.c_str(), offset.c_str(), offset.c_str(),
                                          scaleVec.c_str(), scaleOffsetVec.c_str());
 
                 fragBuilder->appendTextureLookup(&depthMaps[i], args.fTexSamplers[i],
                                                  povCoord.c_str(),
                                                  kVec2f_GrSLType);
+
+
             }
 
             const char* ambientColorUniName = nullptr;
@@ -274,25 +274,45 @@ public:
 
             fragBuilder->codeAppendf("vec4 resultDiffuseColor = %s;", diffuseColor.c_str());
 

[robertphillips, 2016/08/10 14:23:18]

can we parameterize the shadow generation ?

[vjiaoblack, 2016/08/11 18:28:51]

Done.

-            // Essentially,
-            // diffColor * (ambientLightTot + foreachDirLight(lightColor * (N . L)))
+            // all the normal vectors point straight up
             SkString totalLightColor("totalLightColor");
-            fragBuilder->codeAppendf("vec3 %s = vec3(0);", totalLightColor.c_str());
+            fragBuilder->codeAppendf("vec3 %s = vec3(0,0,0);", totalLightColor.c_str());
+
+            SkString lightProb("lightProbability");
+            fragBuilder->codeAppendf("float %s;", lightProb.c_str());
+            fragBuilder->codeAppendf("float variance;");
+            fragBuilder->codeAppendf("float d;");
 
             for (int i = 0; i < numLights; i++) {
-                fragBuilder->codeAppendf("if (%s.b >= %s.b) {",
+                fragBuilder->codeAppendf("%s = 1;", lightProb.c_str());
+
+                // 1/512 is less than half a pixel; imperceptible
+                fragBuilder->codeAppendf("if (%s.b <= %s.b + 1/512) {",
                                          povDepth.c_str(), depthMaps[i].c_str());
-                // Note that dot(vec3(0,0,1), %s) == %s.z * %s
-                fragBuilder->codeAppendf("%s += %s.z * %s;",
+
+                fragBuilder->codeAppendf("vec2 moments = vec2(%s.b * 255,  %s.g * 255 * 256 );",
+                                         depthMaps[i].c_str(), depthMaps[i].c_str());
+
+                // variance biasing lessens light bleeding
+                fragBuilder->codeAppendf("variance = max(moments.y - (moments.x * moments.x),"
+                                                        "1024);");
+
+                fragBuilder->codeAppendf("d = (%s.b * 255) - moments.x;", povDepth.c_str());
+                fragBuilder->codeAppendf("%s = (variance / (variance + d * d));",
+                                         lightProb.c_str());
+
+                // The curved shadows near plane edges are caused by using a non-optimal blurring
+                // function. Optimally, it'd be a linear blur.
+                fragBuilder->codeAppendf("}");
+
+                fragBuilder->codeAppendf("%s += dot(vec3(0,0,1), %s) * %s * %s;",
                                          totalLightColor.c_str(),
                                          lightDirUniName[i],
-                                         lightColorUniName[i]);
-                fragBuilder->codeAppendf("}");
+                                         lightColorUniName[i],
+                                         lightProb.c_str());
             }
 
-            fragBuilder->codeAppendf("%s += %s;",
-                                     totalLightColor.c_str(),
-                                     ambientColorUniName);
+            fragBuilder->codeAppendf("%s += %s;", totalLightColor.c_str(), ambientColorUniName);
 
             fragBuilder->codeAppendf("resultDiffuseColor *= vec4(%s, 1);",
                                      totalLightColor.c_str());