Added presentations from EVI 2017

EVI - 2017/EVI 21/EVIray/sphere.hpp

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+#pragma once
+#ifndef SPHERE_HPP
+#define SPHERE_HPP
+
+#include <glm/glm.hpp>
+
+#include "figure.hpp"
+
+using glm::vec3;
+
+class Sphere : public Figure {
+public:
+  vec3 m_center;
+  float m_radius;
+  
+  Sphere(Material * mat = NULL): Figure(mat), m_center(vec3(0.0f)), m_radius(0.5f) {
+    calculate_inv_area();
+  }
+
+  Sphere(float x, float y, float z, float r, Material * mat = NULL): Figure(mat), m_center(vec3(x, y, z)), m_radius(r) {
+    calculate_inv_area();
+  }
+
+  Sphere(vec3 _c, float r, Material * mat = NULL): Figure(mat), m_center(_c), m_radius(r) {
+    calculate_inv_area();
+  }
+
+  virtual ~Sphere() { }
+
+  virtual bool intersect(Ray & r, float & t) const;
+  virtual vec3 normal_at_int(Ray & r, float & t) const;
+  virtual vec3 sample_at_surface() const;
+
+private:
+  virtual void calculate_inv_area();
+};
+
+#endif