raytracer.cpp

#include <fstream>
#include <cmath>

struct Vec {
    double x, y, z;
    Vec(){x=y=z=0;}
    Vec(double a, double b, double c){x=a,y=b,z=c;}
    Vec operator- (Vec v) {return Vec(x-v.x,y-v.y,z-v.z);}
};

double dot(Vec v, Vec b) {return (v.x*b.x+v.y*b.y+v.z*b.z);}

struct Ray {
    Vec o;          // origin
    Vec d;          // direction
    Ray(Vec i, Vec j) {o=i,d=j;}
};

struct Sphere {
    Vec c;              // Center
    double r;           // Radius
    Sphere(Vec i, double j){c=i, r=j;}
    bool intersect(Ray ray, double &t) {
        Vec o = ray.o;
        Vec d = ray.d;
        Vec oc = o-c;
        double b = 2*dot(oc,d);
        double c = dot(oc, oc)-r*r;
        double disc = b*b-4*c;
        if (disc < 0) return false;
        else {
            disc = sqrt(disc);
            double t0 = -b-disc;
            double t1 = -b+disc;

            t = (t0 < t1) ? t0 : t1;
            return true;
        }
    }
};

struct Color {
    double r,g,b;
    Color(){r=g=b=0;}
    Color(double i, double j, double k){r=i,g=j,b=k;}
};

int main() {

    const int W = 500;          // Image width
    const int H = 500;          // Image height;

    std::ofstream out("out.ppm");
    out << "P3" << std::endl << W << std::endl << H << std::endl << "255" << std::endl;

    Color pixel_col[H][W];

    Color white(255, 255, 255);
    Sphere sphere(Vec(W/2,H/2,50),20);

    // for each pixel
    for (int y = 0; y < H; y++) {
        for (int x = 0; x < W; x++) {

            // send a ray through each pixel
            Ray ray(Vec(x, y, 0),Vec(0, 0, 1));

            double t = 20000;

            // Check for intersections
            if (sphere.intersect(ray,t)) {
                pixel_col[y][x] = white;
            }
            out << pixel_col[y][x].r << std::endl;
            out << pixel_col[y][x].g << std::endl;
            out << pixel_col[y][x].b << std::endl;
        }
    }

    return 0;
}