text: #ifndef PLANE_H
  #define PLANE_H
  
  #include "geometry.h"
  
  /*
   * A plane centered at the origin spanning
   * [-1, -1] to [1, 1] with normal of {0, 0, 1}
   */
  class Plane : public Geometry {
  public:
  	bool intersect(Ray &ray, DifferentialGeometry &diff_geom) const override;
  	BBox bound() const override;
  	void refine(std::vector<Geometry*> &prims) override;
  };
  
  #endif
  
  