snoopy/include/material.h

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#pragma once
#include "hittable.h"
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#include "hit_record.h"
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class material
{
public:
virtual bool scatter(
const ray& r_in,
const hit_record& rec,
colour& attenuation,
ray& scattered) const = 0;
};
class lambertian : public material
{
public:
lambertian(const colour& a) : albedo_(a) {}
virtual bool scatter(
const ray& r_in,
const hit_record& rec,
colour& attenuation,
ray& scattered) const
{
vec3 scatter_direction = rec.normal + vec3::random_unit_vector();
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scattered = ray(rec.p, scatter_direction);
attenuation = albedo_;
return true;
}
private:
colour albedo_;
};
class metal : public material
{
public:
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metal(const colour& a, double f) :
albedo_(a),
fuzz_(f < 1 ? f : 1) {}
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virtual bool scatter(
const ray& r_in,
const hit_record& rec,
colour& attenuation,
ray& scattered) const
{
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vec3 reflected = reflect(normalize(r_in.direction()), rec.normal);
scattered = ray(rec.p, reflected + fuzz_ * vec3::random_in_unit_sphere());
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attenuation = albedo_;
return dot(scattered.direction(), rec.normal) > 0;
}
private:
colour albedo_;
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double fuzz_;
};
class dielectric : public material
{
public:
dielectric(double ri) : refraction_index_(ri) {}
virtual bool scatter(
const ray& r_in,
const hit_record& rec,
colour& attenuation,
ray& scattered) const
{
attenuation = colour(1.0,1.0,1.0);
double etai_over_etat = rec.front_face ? (1.0 / refraction_index_) : refraction_index_;
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vec3 unit_direction = normalize(r_in.direction());
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double cos_theta = fmin(dot(-unit_direction, rec.normal), 1.0);
double sin_theta = sqrt(1.0 - cos_theta*cos_theta);
if (etai_over_etat * sin_theta > 1.0)
{
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vec3 reflected = reflect(unit_direction, rec.normal);
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scattered = ray(rec.p, reflected);
return true;
}
double reflect_prob = schlick(cos_theta, etai_over_etat);
if (math::random_double() < reflect_prob)
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{
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vec3 reflected = reflect(unit_direction, rec.normal);
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scattered = ray(rec.p, reflected);
return true;
}
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vec3 refracted = refract(unit_direction, rec.normal, etai_over_etat);
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scattered = ray(rec.p, refracted);
return true;
}
private:
double refraction_index_;
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double schlick(double cosine, double refraction_index) const
{
auto r0 = (1-refraction_index) / (1+refraction_index);
r0 = r0*r0;
return r0 + (1-r0)*pow(1-cosine, 5);
}
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};