CCEffectRefraction - Disable the refraction effect according to the normal map's alpha channel

If alpha == 0, then you just get the base color and texture but no contribution from the environment.
This is implemented as a multiply not a conditional so alpha values between 0 and 1 will modulate
the environment color.

Author: Thayer J Andrews

Resources/Images/ShinyBallColor.png

@@ -57,9 +57,9 @@ -(void)setupRefractionEffectTest
 
     [self.contentNode addChild:renderTexture];
 
-    NSString *sphereTextureFile = @"Images/sphere-256.png";
+    NSString *sphereTextureFile = @"Images/ShinyBallColor.png";
     CCTexture *sphereTexture = [CCTexture textureWithFile:sphereTextureFile];
-    CCSpriteFrame *sphereNormalMap = [CCSpriteFrame frameWithImageNamed:@"Images/sphere-normal-256.png"];
+    CCSpriteFrame *sphereNormalMap = [CCSpriteFrame frameWithImageNamed:@"Images/ShinyBallNormals.png"];
     CCEffectRefraction *sphereRefraction = [[CCEffectRefraction alloc] initWithRefraction:0.1f environment:renderTexture.sprite normalMap:nil];
 
     p1 = CGPointMake(0.1f, 0.8f);
@@ -76,9 +76,9 @@ -(void)setupRefractionEffectTest
                                                                 ]]];
     [self.contentNode addChild:sprite1];
 
-    NSString *torusTextureFile = @"Images/torus-256.png";
+    NSString *torusTextureFile = @"Images/ShinyTorusColor.png";
     CCTexture *torusTexture = [CCTexture textureWithFile:torusTextureFile];
-    CCSpriteFrame *torusNormalMap = [CCSpriteFrame frameWithImageNamed:@"Images/torus-normal-256.png"];
+    CCSpriteFrame *torusNormalMap = [CCSpriteFrame frameWithImageNamed:@"Images/ShinyTorusNormals.png"];
     CCEffectRefraction *torusRefraction = [[CCEffectRefraction alloc] initWithRefraction:0.1f environment:renderTexture.sprite normalMap:torusNormalMap];
 
     p1 = CGPointMake(0.65f, 0.2f);

Resources/Images/ShinyBallNormals.png

@@ -64,7 +64,8 @@ -(void)buildFragmentFunctions
                                    vec4 envSpaceTexCoords = u_screenToEnv * gl_FragCoord;
 
                                    // Index the normal map and expand the color value from [0..1] to [-1..1]
-                                   vec4 tangentSpaceNormal = texture2D(cc_NormalMapTexture, cc_FragTexCoord2) * 2.0 - 1.0;
+                                   vec4 normalMap = texture2D(cc_NormalMapTexture, cc_FragTexCoord2);
+                                   vec4 tangentSpaceNormal = normalMap * 2.0 - 1.0;
 
                                    // Convert the normal vector from tangent space to environment space
                                    vec2 normal = u_tangent * tangentSpaceNormal.x + u_binormal * tangentSpaceNormal.y;
@@ -79,8 +80,13 @@ -(void)buildFragmentFunctions
                                    // This is 1.0 if both refracted texture coords are in bounds and 0.0 otherwise.
                                    float inBounds = step(0.0, min(compare.x, compare.y));
 
+                                   // Compute the combination of the sprite's color and texture.
                                    vec4 primaryColor = cc_FragColor * texture2D(cc_MainTexture, cc_FragTexCoord1);
-                                   primaryColor += inBounds * texture2D(u_envMap, refractTexCoords) * (1.0 - primaryColor.a);
+
+                                   // If the refracted texture coordinates are within the bounds of the environment map
+                                   // blend the primary color with the refracted environment. Multiplying by the normal
+                                   // map alpha also allows the effect to be disabled for specific pixels.
+                                   primaryColor += inBounds * normalMap.a * texture2D(u_envMap, refractTexCoords) * (1.0 - primaryColor.a);
 
                                    return primaryColor;
                                    );