nuclear@2: #ifndef BRDF_H_
nuclear@2: #define BRDF_H_
nuclear@2: 
nuclear@21: #include <vector>
nuclear@2: #include "texture.h"
nuclear@2: 
nuclear@31: class Material;
nuclear@31: 
nuclear@31: class SurfaceGeometry {
nuclear@31: public:
nuclear@31: 	Vector3 normal, tangent;
nuclear@31: 	Vector2 uv;
nuclear@31: 
nuclear@31: 	enum VecLength { unit, unknown };
nuclear@31: 
nuclear@31: 	explicit SurfaceGeometry(const Vector3 &norm, VecLength st = unknown);
nuclear@31: 	SurfaceGeometry(const Vector3 &norm, const Vector2 &uv, VecLength st = unknown);
nuclear@31: 	SurfaceGeometry(const Vector3 &norm, const Vector3 &tang, VecLength st = unknown);
nuclear@31: 	SurfaceGeometry(const Vector3 &norm, const Vector3 &tang, const Vector2 &uv, VecLength st = unknown);
nuclear@31: 
nuclear@31: 	/** create a cartesian direction vector in sample space (zenith = +Z) and
nuclear@31: 	 * transform it to world space.
nuclear@31: 	 * \param theta the horizontal angle (azimuth, in radians) around the Z axis [0, 2pi]
nuclear@31: 	 * \param phi the vertical angle (elevation, in radians) away from the Z axis [0, pi]
nuclear@31: 	 */
nuclear@31: 	Vector3 spherical_to_world(float theta, float phi) const;
nuclear@31: 	/// transforms a direction vector from sample space (centered around Z) to world space
nuclear@31: 	Vector3 sample_to_world(const Vector3 &v) const;
nuclear@31: 	/// transforms a direction vector from world space to sample space (centered around Z)
nuclear@31: 	Vector3 world_to_sample(const Vector3 &v) const;
nuclear@31: };
nuclear@31: 
nuclear@31: /// abstract bidirection reflectance distribution function base class
nuclear@2: class Reflectance {
nuclear@31: protected:
nuclear@31: 	const Material *mtl;	// pointer to the material we belong to
nuclear@31: 
nuclear@2: public:
nuclear@2: 	Reflectance();
nuclear@31: 	explicit Reflectance(const Material *mtl);
nuclear@2: 	virtual ~Reflectance() = default;
nuclear@2: 
nuclear@31: 	void set_material(const Material *mtl);
nuclear@31: 	const Material *get_material() const;
nuclear@31: 
nuclear@31: 	/// given an outgoing light direction generate an incidence direction to sample the BRDF
nuclear@31: 	virtual Vector3 sample_dir(const SurfaceGeometry &geom, const Vector3 &outdir) const = 0;
nuclear@31: 	/// given an outgoing direction, generate an incidence direction, and evaluate its probability
nuclear@31: 	virtual float sample(const SurfaceGeometry &geom, const Vector3 &outdir, Vector3 *indir) const;
nuclear@31: 	/// given an outgoing direction and an incidence direction, evaluate the probability of this path
nuclear@31: 	virtual float eval(const SurfaceGeometry &geom, const Vector3 &outdir, const Vector3 &indir) const = 0;
nuclear@2: };
nuclear@2: 
nuclear@31: typedef float (*CompReflWeightFunc)(const SurfaceGeometry &geom, const Vector3 &outdir);
nuclear@21: 
nuclear@31: /// composite BRDF, with multiple weighted sub-reflectances.
nuclear@21: class CompositeRefl : public Reflectance {
nuclear@21: private:
nuclear@21: 	struct SubRefl {
nuclear@21: 		Reflectance *brdf;
nuclear@21: 		float weight;
nuclear@21: 		CompReflWeightFunc weight_func;	// if null, use static weight above
nuclear@21: 	};
nuclear@21: 	std::vector<SubRefl> sub_brdf;
nuclear@21: 	mutable bool valid_checked;
nuclear@21: 
nuclear@31: 	int pick_brdf(const SurfaceGeometry &geom, const Vector3 &outdir) const;
nuclear@21: 
nuclear@21: public:
nuclear@21: 	CompositeRefl();
nuclear@31: 	explicit CompositeRefl(const Material *mtl);
nuclear@21: 
nuclear@21: 	virtual void add_brdf(Reflectance *brdf, float weight);
nuclear@21: 	virtual void add_brdf(Reflectance *brdf, CompReflWeightFunc weight_func);
nuclear@21: 
nuclear@21: 	bool check_valid() const;
nuclear@21: 
nuclear@31: 	Vector3 sample_dir(const SurfaceGeometry &geom, const Vector3 &outdir) const override;
nuclear@31: 	float sample(const SurfaceGeometry &geom, const Vector3 &outdir, Vector3 *indir) const override;
nuclear@31: 	float eval(const SurfaceGeometry &geom, const Vector3 &outdir, const Vector3 &indir) const override;
nuclear@21: };
nuclear@21: 
nuclear@31: /// lambertian perfect diffuse reflectance
nuclear@2: class LambertRefl : public Reflectance {
nuclear@2: public:
nuclear@31: 	Vector3 sample_dir(const SurfaceGeometry &geom, const Vector3 &outdir) const override;
nuclear@31: 	float eval(const SurfaceGeometry &geom, const Vector3 &outdir, const Vector3 &indir) const override;
nuclear@2: };
nuclear@2: 
nuclear@31: /// perfect specular reflectance
nuclear@21: class MirrorRefl : public Reflectance {
nuclear@21: public:
nuclear@31: 	Vector3 sample_dir(const SurfaceGeometry &geom, const Vector3 &outdir) const override;
nuclear@31: 	float eval(const SurfaceGeometry &geom, const Vector3 &outdir, const Vector3 &indir) const override;
nuclear@21: };
nuclear@21: 
nuclear@31: /// glossy phong reflectance with lafortune sampling
nuclear@28: class PhongRefl : public Reflectance {
nuclear@28: public:
nuclear@31: 	Vector3 sample_dir(const SurfaceGeometry &geom, const Vector3 &outdir) const override;
nuclear@31: 	float eval(const SurfaceGeometry &geom, const Vector3 &outdir, const Vector3 &indir) const override;
nuclear@28: };
nuclear@28: 
nuclear@2: #endif	// BRDF_H_