rewrite Light class using Eigen

src/Light.h

@@ -1,16 +1,55 @@
 #ifndef LIGHT_H_
 #define LIGHT_H_
 
-enum LIGHT_TYPE { POINT, AREA };
+#include <Eigen/Core>
 
+using Eigen::Matrix;
+using Eigen::Matrix4f;
+using Eigen::Vector3f;
+
+// Abstract base class for Lights
 class Light {
 public:
-  Light(LIGHT_TYPE, float *, float *);
+  enum class Type { Point, Area };
+
+  virtual ~Light() = default;
+
+  // a pure virtual function for derived class implementation
+  virtual void illumination() const = 0;
+
+protected:
+  Light(Type type, const Vector3f &id, const Vector3f &is)
+      : type(type), diffuse(id), specular(is) {}
+
+  Type type;
+  Vector3f diffuse;                          // mandatory member `id`
+  Vector3f specular;                         // mandatory member `is`
+  Matrix4f transform = Matrix4f::Identity(); // optional member `transform`
+  unsigned int gridSize = 0;                 // optional member `n`
+  bool useCenter = false;                    // optional member `usecenter`
+};
+
+class PointLight : public Light {
+public:
+  PointLight(const Vector3f &id, const Vector3f &is, Vector3f &center)
+      : Light(Type::Point, id, is), center(center) {}
+
+  virtual void illumination() const override;
 
 private:
-  LIGHT_TYPE type;
-  float diffuse[3];  // field `id`
-  float specular[3]; // field `is`
+  Vector3f center;
+};
+
+class AreaLight : public Light {
+public:
+  AreaLight(const Vector3f &id, const Vector3f &is,
+            const Matrix<float, 3, 4> &corners)
+      : Light(Type::Area, id, is), corners(corners) {}
+
+  virtual void illumination() const override;
+
+private:
+  Matrix<float, 3, 4> corners; // stores `p1`, `p2`, `p3` and `p4`
 };
 
 #endif // !LIGHT_H_