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MT version of smallpt (http://www.kevinbeason.com/smallpt/)
#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <random>
#include <iostream>
#include <intrin.h>
#include <stdint.h>
#include <chrono>
#define M_PI 3.14159265358979323846
namespace ch = std::chrono;
struct Vec { // Usage: time ./smallpt 5000 && xv image.ppm
double x, y, z; // position, also color (r,g,b)
Vec(double x_=0, double y_=0, double z_=0){ x=x_; y=y_; z=z_; }
Vec operator+(const Vec &b) const { return Vec(x+b.x,y+b.y,z+b.z); }
Vec operator-(const Vec &b) const { return Vec(x-b.x,y-b.y,z-b.z); }
Vec operator*(double b) const { return Vec(x*b,y*b,z*b); }
Vec mult(const Vec &b) const { return Vec(x*b.x,y*b.y,z*b.z); }
Vec& norm(){ return *this = *this * (1/sqrt(x*x+y*y+z*z)); }
double dot(const Vec &b) const { return x*b.x+y*b.y+z*b.z; } // cross:
Vec operator%(Vec&b){return Vec(y*b.z-z*b.y,z*b.x-x*b.z,x*b.y-y*b.x);}
};
struct Ray { Vec o, d; Ray(Vec o_, Vec d_) : o(o_), d(d_) {} };
enum Refl_t { DIFF, SPEC, REFR }; // material types, used in radiance()
struct Sphere {
double rad; // radius
Vec p, e, c; // position, emission, color
Refl_t refl; // reflection type (DIFFuse, SPECular, REFRactive)
Sphere(double rad_, Vec p_, Vec e_, Vec c_, Refl_t refl_):
rad(rad_), p(p_), e(e_), c(c_), refl(refl_) {}
double intersect(const Ray &r) const { // returns distance, 0 if nohit
Vec op = p-r.o; // Solve t^2*d.d + 2*t*(o-p).d + (o-p).(o-p)-R^2 = 0
double t, eps=1e-4, b=op.dot(r.d), det=b*b-op.dot(op)+rad*rad;
if (det<0) return 0; else det=sqrt(det);
return (t=b-det)>eps ? t : ((t=b+det)>eps ? t : 0);
}
};
Sphere spheres[] = {//Scene: radius, position, emission, color, material
Sphere(1e5, Vec( 1e5+1,40.8,81.6), Vec(),Vec(.75,.25,.25),DIFF),//Left
Sphere(1e5, Vec(-1e5+99,40.8,81.6),Vec(),Vec(.25,.25,.75),DIFF),//Rght
Sphere(1e5, Vec(50,40.8, 1e5), Vec(),Vec(.75,.75,.75),DIFF),//Back
Sphere(1e5, Vec(50,40.8,-1e5+170), Vec(),Vec(), DIFF),//Frnt
Sphere(1e5, Vec(50, 1e5, 81.6), Vec(),Vec(.75,.75,.75),DIFF),//Botm
Sphere(1e5, Vec(50,-1e5+81.6,81.6),Vec(),Vec(.75,.75,.75),DIFF),//Top
Sphere(16.5,Vec(27,16.5,47), Vec(),Vec(1,1,1)*.999, SPEC),//Mirr
Sphere(16.5,Vec(73,16.5,78), Vec(),Vec(1,1,1)*.999, REFR),//Glas
Sphere(600, Vec(50,681.6-.27,81.6),Vec(12,12,12), Vec(), DIFF) //Lite
};
inline double clamp(double x){ return x<0 ? 0 : x>1 ? 1 : x; }
inline int toInt(double x){ return int(pow(clamp(x),1/2.2)*255+.5); }
inline bool intersect(const Ray &r, double &t, int &id){
double n=sizeof(spheres)/sizeof(Sphere), d, inf=t=1e20;
for(int i=int(n);i--;) if((d=spheres[i].intersect(r))&&d<t){t=d;id=i;}
return t<inf;
}
class Random
{
public:
Random(unsigned int s) { engine.seed(s); }
double Next() { return uniformReal(engine); }
private:
std::mt19937 engine;
std::uniform_real_distribution<double> uniformReal;
};
double mtrand(Random& rng)
{
return rng.Next();
}
Vec radiance(const Ray &r, int depth, Random& rng)
{
double t; // distance to intersection
int id=0; // id of intersected object
if (!intersect(r, t, id)) return Vec(); // if miss, return black
const Sphere &obj = spheres[id]; // the hit object
Vec x=r.o+r.d*t, n=(x-obj.p).norm(), nl=n.dot(r.d)<0?n:n*-1, f=obj.c;
double p = f.x>f.y && f.x>f.z ? f.x : f.y>f.z ? f.y : f.z; // max refl
if (++depth>5) if (mtrand(rng)<p) f=f*(1/p); else return obj.e; //R.R.
if (obj.refl == DIFF){ // Ideal DIFFUSE reflection
double r1=2*M_PI*mtrand(rng), r2=mtrand(rng), r2s=sqrt(r2);
Vec w=nl, u=((fabs(w.x)>.1?Vec(0,1):Vec(1))%w).norm(), v=w%u;
Vec d = (u*cos(r1)*r2s + v*sin(r1)*r2s + w*sqrt(1-r2)).norm();
return obj.e + f.mult(radiance(Ray(x,d),depth,rng));
} else if (obj.refl == SPEC) // Ideal SPECULAR reflection
return obj.e + f.mult(radiance(Ray(x,r.d-n*2*n.dot(r.d)),depth,rng));
Ray reflRay(x, r.d-n*2*n.dot(r.d)); // Ideal dielectric REFRACTION
bool into = n.dot(nl)>0; // Ray from outside going in?
double nc=1, nt=1.5, nnt=into?nc/nt:nt/nc, ddn=r.d.dot(nl), cos2t;
if ((cos2t=1-nnt*nnt*(1-ddn*ddn))<0) // Total internal reflection
return obj.e + f.mult(radiance(reflRay,depth,rng));
Vec tdir = (r.d*nnt - n*((into?1:-1)*(ddn*nnt+sqrt(cos2t)))).norm();
double a=nt-nc, b=nt+nc, R0=a*a/(b*b), c = 1-(into?-ddn:tdir.dot(n));
double Re=R0+(1-R0)*c*c*c*c*c,Tr=1-Re,P=.25+.5*Re,RP=Re/P,TP=Tr/(1-P);
return obj.e + f.mult(depth>2 ? (mtrand(rng)<P ? // Russian roulette
radiance(reflRay,depth,rng)*RP:radiance(Ray(x,tdir),depth,rng)*TP) :
radiance(reflRay,depth,rng)*Re+radiance(Ray(x,tdir),depth,rng)*Tr);
}
int main(int argc, char *argv[])
{
auto start = ch::high_resolution_clock::now();
int w=1024, h=768, samps = argc==2 ? atoi(argv[1])/4 : 1; // # samples
Ray cam(Vec(50,52,295.6), Vec(0,-0.042612,-1).norm()); // cam pos, dir
Vec cx=Vec(w*.5135/h), cy=(cx%cam.d).norm()*.5135, r, *c=new Vec[w*h];
#pragma omp parallel for schedule(dynamic, 1) private(r) // OpenMP
for (int y=0; y<h; y++)
{ // Loop over image rows
fprintf(stderr,"\rRendering (%d spp) %5.2f%%",samps*4,100.*y/(h-1));
Random rng(y);
for (unsigned short x=0; x<w; x++) // Loop cols
{
for (int sy=0, i=(h-y-1)*w+x; sy<2; sy++) // 2x2 subpixel rows
{
for (int sx=0; sx<2; sx++, r=Vec()) // 2x2 subpixel cols
{
for (int s=0; s<samps; s++)
{
double r1=2*mtrand(rng), dx=r1<1 ? sqrt(r1)-1: 1-sqrt(2-r1);
double r2=2*mtrand(rng), dy=r2<1 ? sqrt(r2)-1: 1-sqrt(2-r2);
Vec d = cx*( ( (sx+.5 + dx)/2 + x)/w - .5) + cy*( ( (sy+.5 + dy)/2 + y)/h - .5) + cam.d;
r = r + radiance(Ray(cam.o+d*140,d.norm()),0,rng)*(1./samps);
} // Camera rays are pushed ^^^^^ forward to start in interior
c[i] = c[i] + Vec(clamp(r.x),clamp(r.y),clamp(r.z))*.25;
}
}
}
}
auto end = ch::high_resolution_clock::now();
double elapsed = (double)ch::duration_cast<ch::milliseconds>(end - start).count() / 1000.0;
std::cout << std::endl;
std::cout << "Elapsed : " << elapsed << " seconds" << std::endl;
FILE *f = fopen("image.ppm", "w"); // Write image to PPM file.
fprintf(f, "P3\n%d %d\n%d\n", w, h, 255);
for (int i=0; i<w*h; i++)
fprintf(f,"%d %d %d ", toInt(c[i].x), toInt(c[i].y), toInt(c[i].z));
}
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