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82 lines
2.2 KiB
C++
82 lines
2.2 KiB
C++
#ifndef SPHERE_H
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#define SPHERE_H
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#include "color.h"
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#include "ray.h"
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#include "vec3.h"
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#include <cmath>
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#include <optional>
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#include <tuple>
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enum class Material : int {
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Lambertian = 0,
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Metal,
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Dielectric,
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Undefined
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};
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struct Sphere
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{
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point3 center;
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double radius;
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Material M;
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color tint;
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std::pair<color, ray> scatter(const ray& r, double root) const {
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const auto p = r.at(root);
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auto normal = (p - center) / radius;
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if (M == Material::Lambertian) {
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return {tint, ray(p, normal + randomUnitSphere())};
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} else if (M == Material::Metal) {
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return {tint, ray(p, r.direction().reflect(normal))};
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} else if (M == Material::Dielectric) {
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constexpr auto index = 1.0 / 1.33;
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const bool front = r.direction().dot(normal) < 0;
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const auto ri = front ? 1.0 / index : index;
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if (!front)
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normal *= -1;
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const auto dir = r.direction().normalize();
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const double costh = std::fmin((-dir).dot(normal), 1);
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const double sinth = std::sqrt(1 - costh * costh);
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if (ri * sinth > 1)
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return {color(1, 1, 1), ray(p, dir.reflect(normal))};
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else
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return {color(1, 1, 1), ray(p, dir.refract(normal, ri))};
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} else {
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return {};
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}
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}
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std::optional<double> hit(const ray& r, double tmin, double tmax) const {
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const vec3 oc = center - r.origin();
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const auto a = r.direction().length_squared();
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const auto h = r.direction().dot(oc);
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const auto c = oc.length_squared() - radius * radius;
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const auto discriminant = h * h - a * c;
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if (discriminant < 0) {
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return {}; // No hit
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} else {
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const auto sqrtd = std::sqrt(discriminant);
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// Find the nearest root that lies in the acceptable range.
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auto root = (h - sqrtd) / a;
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if (root <= tmin || tmax <= root) {
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root = (h + sqrtd) / a;
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if (root <= tmin || tmax <= root)
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return {};
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}
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return root;
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}
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}
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};
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#endif // SPHERE_H
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