Added distance attenuation and diffuse shading to PointLights

include/core/SkLights.h

 
 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkLights_DEFINED
 #define SkLights_DEFINED
@@ skipping 13 matching lines @@
         enum LightType {
             kAmbient_LightType,       // only 'fColor' is used
             kDirectional_LightType,
             kPoint_LightType
         };
 
         Light(const Light& other)
             : fType(other.fType)
             , fColor(other.fColor)
             , fDirection(other.fDirection)
+            , fIntensity(other.fIntensity)
             , fShadowMap(other.fShadowMap) {
         }
 
         Light(Light&& other)
             : fType(other.fType)
             , fColor(other.fColor)
             , fDirection(other.fDirection)
+            , fIntensity(other.fIntensity)
             , fShadowMap(std::move(other.fShadowMap)) {
         }
 
         static Light MakeAmbient(const SkColor3f& color) {
             return Light(kAmbient_LightType, color, SkVector3::Make(0.0f, 0.0f, 1.0f));
         }
 
         static Light MakeDirectional(const SkColor3f& color, const SkVector3& dir) {
             Light light(kDirectional_LightType, color, dir);
             if (!light.fDirection.normalize()) {
                 light.fDirection.set(0.0f, 0.0f, 1.0f);
             }
             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; }
         const SkColor3f& color() const { return fColor; }
         const SkVector3& dir() const {
             SkASSERT(kDirectional_LightType == fType);
             return fDirection;
         }
         const SkPoint3& pos() const {
             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);
         }
 
         SkImage* getShadowMap() const {
             return fShadowMap.get();
         }
 
         Light& operator= (const Light& b) {
             if (this == &b) {
                 return *this;
             }
 
             fColor = b.fColor;
             fType = b.fType;
             fDirection = b.fDirection;
             fShadowMap = b.fShadowMap;
             return *this;
         }
     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.

         }
     };
 
     class Builder {
     public:
         Builder() : fLights(new SkLights) { }
 
         void add(const Light& light) {
             if (fLights) {
                 fLights->fLights.push_back(light);
@@ skipping 30 matching lines @@
 
     void flatten(SkWriteBuffer& buf) const;
 
 private:
     SkLights() {}
     SkTArray<Light> fLights;
     typedef SkRefCnt INHERITED;
 };
 
 #endif