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[[File:Ray_trace_diagram.svg.png]]
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struct Vec3 {
double x, y, z;
Vec3(double x, double y, double z) : x(x), y(y), z(z) {}
Vec3 operator + (const Vec3& v) const { return Vec3(x + v.x, y + v.y, z + v.z); }
Vec3 operator - (const Vec3& v) const { return Vec3(x - v.x, y - v.y, z - v.z); }
Vec3 operator * (double d) const { return Vec3(x*d, y*d, z*d); }
Vec3 operator / (double d) const { return Vec3(x / d, y / d, z / d); }
Vec3 normalize() const {
double mg = sqrt(x*x + y*y + z*z);
return Vec3(x / mg, y / mg, z / mg);
}
};
inline double dot(const Vec3& a, const Vec3& b) {
return (a.x*b.x + a.y*b.y + a.z*b.z);
}
struct Ray {
Vec3 o, d;
Ray(const Vec3& o, const Vec3& d) : o(o), d(d) {}
};
struct Sphere {
Vec3 c;
double r;
Sphere(const Vec3& c, double r) : c(c), r(r) {}
Vec3 getNormal(const Vec3& pi) const { return (pi - c) / r; }
bool intersect(const Ray& ray, double &t) const {
const Vec3 o = ray.o;
const Vec3 d = ray.d;
const Vec3 oc = o - c;
const double b = 2 * dot(oc, d);
const double c = dot(oc, oc) - r*r;
double disc = b*b - 4 * c;
if (disc < 1e-4) return false;
disc = sqrt(disc);
const double t0 = -b - disc;
const double t1 = -b + disc;
t = (t0 < t1) ? t0 : t1;
return true;
}
};
int main() {
steady_clock::time_point ts, te,tm;
ts = steady_clock::now();
const int N = 500;
const Vec3 white(255, 255, 255);
const Vec3 black(0, 0, 0);
const Vec3 red(0, 255, 0);
const Sphere sphere(Vec3(N*0.5, N*0.5, 50), 50);
const Sphere light(Vec3(0, 0, 50), 1);
std::ofstream out("out.ppm");
out << "P3\n" << N << ' ' << N << ' ' << "255\n";
double t;
Vec3 pix_col(black);
int* pixs = new int[N * N * 3];
for (int y = 0; y < N; ++y) {
for (int x = 0; x < N; ++x) {
pix_col = black;
const Ray ray(Vec3(x, y, 0), Vec3(0, 0, 1));
if (sphere.intersect(ray, t)) {
const Vec3 pi = ray.o + ray.d*t;
const Vec3 L = light.c - pi;
const Vec3 N = sphere.getNormal(pi);
const double dt = dot(L.normalize(), N.normalize());
pix_col = (red + white*dt) * 0.5;
clamp255(pix_col);
}
pixs[3 * (y * N + x)] = (int)pix_col.x;
pixs[3 * (y * N + x) + 1] = (int)pix_col.y;
pixs[3 * (y * N + x) + 2] = (int)pix_col.z;
}
}
te = steady_clock::now();
reportTime("matrix-matrix multiplication", te - ts);
for (int y = 0; y < N; ++y) {
for (int x = 0; x < N; ++x) {
out << pixs[3 * (y * N + x)] << ' '
<< pixs[3 * (y * N + x) + 1] << ' '
<< pixs[3 * (y * N + x) + 2] << '\n';
}
}
tm = steady_clock::now();
reportTime("matrix-matrix multiplication", tm - ts);
delete[] pixs;
}
