CCEffectLighting - First pass at specular highlights

It works but there are a few things missing:
1) Highlights are always enabled.
2) There is no shininess control (i.e. no way to change the specular exponent).
3) There is no specular material color (it's always assumed to be white).

Author: Thayer J Andrews

cocos2d/CCEffectLighting.m

@@ -85,36 +85,49 @@ +(NSMutableArray *)buildFragmentFunctionsWithLights:(NSArray*)lights
     [effectBody appendString:CC_GLSL(
                                      // Index the normal map and expand the color value from [0..1] to [-1..1]
                                      vec4 normalMap = texture2D(cc_NormalMapTexture, cc_FragTexCoord2);
-                                     vec4 tangentSpaceNormal = normalMap * 2.0 - 1.0;
+                                     vec3 tangentSpaceNormal = normalize(normalMap.xyz * 2.0 - 1.0);
 
                                      if (normalMap.a == 0.0)
                                      {
                                          return vec4(0,0,0,0);
                                      }
 
                                      vec4 lightColor;
-                                     vec4 tangentSpaceLightDir;
-                                     vec4 resultColor = u_globalAmbientColor;
+                                     vec4 diffuseLightColor = u_globalAmbientColor;
+                                     vec4 specularLightColor = vec4(0,0,0,1);
+                                     
+                                     vec3 tangentSpaceLightDir;
+                                     vec3 halfAngleDir;
+                                     
                                      float lightDist;
+                                     float falloffTerm;
+                                     float diffuseTerm;
+                                     float specularTerm;
                                      )];
 
     for (NSUInteger lightIndex = 0; lightIndex < lights.count; lightIndex++)
     {
         CCLightNode *light = lights[lightIndex];
         if (light.type == CCLightDirectional)
         {
-            [effectBody appendFormat:@"tangentSpaceLightDir = v_tangentSpaceLightDir%lu;\n", (unsigned long)lightIndex];
+            [effectBody appendFormat:@"tangentSpaceLightDir = v_tangentSpaceLightDir%lu.xyz;\n", (unsigned long)lightIndex];
             [effectBody appendFormat:@"lightColor = u_lightColor%lu;\n", (unsigned long)lightIndex];
         }
         else
         {
-            [effectBody appendFormat:@"tangentSpaceLightDir = normalize(v_tangentSpaceLightDir%lu);\n", (unsigned long)lightIndex];
-            [effectBody appendFormat:@"lightDist = length(v_tangentSpaceLightDir%lu);\n", (unsigned long)lightIndex];
-            [effectBody appendFormat:@"lightColor = u_lightColor%lu * max(0.0, (1.0 - lightDist * u_lightFalloff%lu));\n", (unsigned long)lightIndex, (unsigned long)lightIndex];
+            [effectBody appendFormat:@"tangentSpaceLightDir = normalize(v_tangentSpaceLightDir%lu.xyz);\n", (unsigned long)lightIndex];
+            [effectBody appendFormat:@"lightDist = length(v_tangentSpaceLightDir%lu.xyz);\n", (unsigned long)lightIndex];
+            [effectBody appendFormat:@"falloffTerm = max(0.0, (1.0 - lightDist * u_lightFalloff%lu));\n", (unsigned long)lightIndex];
+            [effectBody appendFormat:@"lightColor = u_lightColor%lu * falloffTerm;\n", (unsigned long)lightIndex];
         }
-        [effectBody appendFormat:@"resultColor += lightColor * max(0.0, dot(tangentSpaceNormal, tangentSpaceLightDir));\n"];
+        [effectBody appendString:@"diffuseTerm = max(0.0, dot(tangentSpaceNormal, tangentSpaceLightDir));\n"];
+        [effectBody appendString:@"diffuseLightColor += lightColor * diffuseTerm;\n"];
+        
+        [effectBody appendString:@"halfAngleDir = (2.0 * dot(tangentSpaceLightDir, tangentSpaceNormal) * tangentSpaceNormal - tangentSpaceLightDir);\n"];
+        [effectBody appendString:@"specularTerm = max(0.0, dot(halfAngleDir, vec3(0,0,1))) * step(0.0, diffuseTerm);\n"];
+        [effectBody appendString:@"specularLightColor += lightColor * pow(specularTerm, 10.0);\n"];
     }
-    [effectBody appendString:@"return resultColor * inputValue;\n"];
+    [effectBody appendString:@"return diffuseLightColor * inputValue + specularLightColor;\n"];
 
     CCEffectFunction* fragmentFunction = [[CCEffectFunction alloc] initWithName:@"lightingEffectFrag" body:effectBody inputs:@[input] returnType:@"vec4"];
     return [NSMutableArray arrayWithObject:fragmentFunction];