61 lines
2.0 KiB
C++
61 lines
2.0 KiB
C++
#include <iostream>
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#include <cmath>
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#include "color.h"
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#include "vec3.h"
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#include "ray.h"
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double hit_sphere(const Point3& center, double radius, const Ray& r) {
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Vec3 oc = r.origin() - center;
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auto a = r.direction().length_squared();
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auto half_b = dot(oc, r.direction());
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auto c = oc.length_squared() - radius * radius;
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auto disciminant = half_b*half_b - a*c;
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if (disciminant < 0) {
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return -1.0;
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} else {
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return (-half_b - std::sqrt(disciminant)) / a;
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}
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}
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Color ray_color(const Ray& r) {
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auto sphere_center = Point3(0, 0, -1);
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auto t = hit_sphere(sphere_center, 0.5, r);
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if (t > 0.0) {
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Vec3 n = unit_vector(r.at(t) - sphere_center);
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return 0.5 * Color(n.x()+1, n.y()+1, n.z()+1);
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}
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Vec3 unit_direction = unit_vector(r.direction());
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t = 0.5 * (unit_direction.y() + 1.0);
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return (1.0 - t) * Color(1.0, 1.0, 1.0) + t * Color(0.5, 0.7, 1.0);
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}
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int main() {
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const auto aspect_ratio = 16.0 / 9.0;
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const int image_width = 1280;
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const int image_height = static_cast<int>(image_width / aspect_ratio);
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std::cout << "P3\n" << image_width << " " << image_height << "\n255\n";
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auto viewport_height = 2.0;
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auto viewport_width = aspect_ratio * viewport_height;
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auto focal_length = 1.0;
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auto origin = Point3(0, 0, 0);
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auto horizontal = Vec3(viewport_width, 0, 0);
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auto vertical = Vec3(0, viewport_height, 0);
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auto lower_left_corner = origin - horizontal/2 - vertical/2 - Vec3(0, 0, focal_length);
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for (int j = image_height - 1; j >= 0; --j) {
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std::cerr << "\rScanlines remaining: " << j << " " << std::flush;
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for (int i = 0; i < image_width; ++i) {
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auto u = double(i) / (image_width - 1);
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auto v = double(j) / (image_height - 1);
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Ray r(origin, lower_left_corner + u*horizontal + v*vertical - origin);
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Color pixel_color = ray_color(r);
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write_color(std::cout, pixel_color);
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}
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}
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std::cerr << "\nDone.\n";
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}
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