63 lines
1.8 KiB
C++
63 lines
1.8 KiB
C++
#include "color.h"
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#include "ray.h"
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#include "vec3.h"
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#include <iostream>
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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 discriminant = half_b*half_b - a*c;
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if (discriminant < 0) {
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return -1.0;
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} else {
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return (-half_b - sqrt(discriminant)) / a;
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}
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}
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color ray_color(const ray& r) {
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auto t = hit_sphere(point3(0, 0, -1), 0.5, r);
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if (t > 0.0) {
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vec3 N = unit_vector(r.at(t) - vec3(0, 0, -1));
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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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// Image
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const auto aspect_ratio = 16.0 / 9.0;
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const int image_width = 400;
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const int image_height = static_cast<int>(image_width / aspect_ratio);
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// Camera
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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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// Render
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std::cout<<"P3\n"<<image_width<<" "<<image_height<<"\n255\n";
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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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