/******************************************************************/
/* This file is part of the homework assignments for CSCI-427/527 */
/* at The College of William & Mary and authored by Pieter Peers. */
/* No part of this file, whether altered or in original form, can */
/* be distributed or used outside the context of CSCI-427/527     */
/* without consent of either the College of William & Mary or     */
/* Pieter Peers.                                                  */
/******************************************************************/
#ifndef _BRDF_BASE_H_
#define _BRDF_BASE_H_

#include <ostream>
#include "vec3d.h"
#include "color.h"
#include "brdfSample.h"

class brdf_base {
 public:
  /////////////
  // Methods //
  /////////////

  // Note: 'in' and 'out' point away from the surface point
  // Note: 'in' and 'out' are specified in the local shading frame,
  //       where the normal=(0.0, 0.0, 1.0).
  virtual color shade(const vec3d& in, const vec3d& out) const = 0;

  // Same convention for in and out.
  // Returns: reflected radiance
  virtual color reflectance(const vec3d& in, const vec3d& out) const = 0;

  // Same convention for in and out.
  // r1 and r2 are two uniform random variables.
  // Returns: brdfSample record
  virtual brdfSample sample(const vec3d& in, float r1, float r2) const = 0;

  // returns true if BRDF has a specular/diffuse component
  virtual bool isSpecular(void) const = 0;
  virtual bool isDiffuse(void) const = 0;

  // return the total reflectivity of the mateterial
  virtual float reflectivity(void) const = 0;

  /////////////
  // Friends //
  /////////////
  friend std::ostream& operator<<(std::ostream& s, const brdf_base& b)
  {
    b._print(s);
    return s;
  }

 private:
  /////////////////////
  // Private Methods //
  /////////////////////
  virtual void _print(std::ostream& s) const = 0;
};

#endif /* _BRDF_BASE_H_ */