Added distance attenuation and diffuse shading to PointLights

include/core/SkLights.h

Index: include/core/SkLights.h
diff --git a/include/core/SkLights.h b/include/core/SkLights.h
index d9ec65b9aafe59f8766fcad3bda7f4ef9683b37e..597dd201cf1820e71ae4cf8fd661ce85b03983e9 100644
--- a/include/core/SkLights.h
+++ b/include/core/SkLights.h
@@ -31,6 +31,7 @@ public:
             : fType(other.fType)
             , fColor(other.fColor)
             , fDirection(other.fDirection)
+            , fIntensity(other.fIntensity)
             , fShadowMap(other.fShadowMap) {
         }
 
@@ -38,6 +39,7 @@ public:
             : fType(other.fType)
             , fColor(other.fColor)
             , fDirection(other.fDirection)
+            , fIntensity(other.fIntensity)
             , fShadowMap(std::move(other.fShadowMap)) {
         }
 
@@ -53,8 +55,10 @@ public:
             return light;
         }
 
-        static Light MakePoint(const SkColor3f& color, const SkPoint3& pos) {
-            return Light(kPoint_LightType, color, pos);
+        static Light MakePoint(const SkColor3f& color, const SkPoint3& pos, SkScalar intensity) {
+            Light light(kPoint_LightType, color, pos);
+            light.fIntensity = intensity;
+            return light;
         }
 
         LightType type() const { return fType; }
@@ -67,6 +71,10 @@ public:
             SkASSERT(kPoint_LightType == fType);
             return fDirection;
         }
+        SkScalar intensity() const {
+            SkASSERT(kPoint_LightType == fType);
+            return fIntensity;
+        }
 
         void setShadowMap(sk_sp<SkImage> shadowMap) {
             fShadowMap = std::move(shadowMap);
@@ -90,16 +98,21 @@ public:
     private:
         LightType   fType;
         SkColor3f   fColor;           // linear (unpremul) color. Range is 0..1 in each channel.
+
         SkVector3   fDirection;       // For directional lights, holds the direction towards the

[jvanverth1, 2016/08/17 19:59:02]

Reusing the name fDirection for point lights seems odd to me. Maybe fDirOrPos?

[vjiaoblack, 2016/08/18 14:52:18]

Done.

                                       // light (+Z is out of the screen).
                                       // If degenerate, it will be replaced with (0, 0, 1).
                                       // For point lights, holds location of point light
+
+        SkScalar    fIntensity;       // Dictates the light intensity. Basically this divides

[jvanverth1, 2016/08/17 19:59:02]

You need to mention that this is only used for point lights. And the equation
should be I * (n dot L) * color / dist^2. That would be clearer and get rid of
the divide.

[vjiaoblack, 2016/08/18 14:52:18]

That equation would also provide a slightly incorrect equation / different
effect than what I originally coded as, which is fine.

+                                      // the dist^2 attenuation variable to increase brightness.
         sk_sp<SkImage> fShadowMap;
 
         Light(LightType type, const SkColor3f& color, const SkVector3& dir) {
             fType = type;
             fColor = color;
             fDirection = dir;
+            fIntensity = 0.0f;

[jvanverth1, 2016/08/17 19:59:02]

SK_ScalarZero

[vjiaoblack, 2016/08/18 14:52:18]

This does not exist. SK_ScalarNearlyZero exists, but I'm sure that's not the
same.

         }
     };