Scratchapixel 2.0
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raytracer.cpp
// [header] // A very basic raytracer example. // [/header] // [compile] // c++ -o raytracer -O3 -Wall raytracer.cpp // [/compile] // [ignore] // Copyright (C) 2012 www.scratchapixel.com // // This program is free software: you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by // the Free Software Foundation, either version 3 of the License, or // (at your option) any later version. // // This program is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // // You should have received a copy of the GNU General Public License // along with this program. If not, see <http://www.gnu.org/licenses/>. // [/ignore] #include <cstdlib> #include <cstdio> #include <cmath> #include <fstream> #include <vector> #include <iostream> #include <cassert> #if defined __linux__ || defined __APPLE__ // "Compiled for Linux #else // Windows doesn't define these values by default, Linux does #define M_PI 3.141592653589793 #define INFINITY 1e8 #endif template<typename T> class Vec3 { public: T x, y, z; Vec3() : x(T(0)), y(T(0)), z(T(0)) {} Vec3(T xx) : x(xx), y(xx), z(xx) {} Vec3(T xx, T yy, T zz) : x(xx), y(yy), z(zz) {} Vec3& normalize() { T nor2 = length2(); if (nor2 > 0) { T invNor = 1 / sqrt(nor2); x *= invNor, y *= invNor, z *= invNor; } return *this; } Vec3<T> operator * (const T &f) const { return Vec3<T>(x * f, y * f, z * f); } Vec3<T> operator * (const Vec3<T> &v) const { return Vec3<T>(x * v.x, y * v.y, z * v.z); } T dot(const Vec3<T> &v) const { return x * v.x + y * v.y + z * v.z; } Vec3<T> operator - (const Vec3<T> &v) const { return Vec3<T>(x - v.x, y - v.y, z - v.z); } Vec3<T> operator + (const Vec3<T> &v) const { return Vec3<T>(x + v.x, y + v.y, z + v.z); } Vec3<T>& operator += (const Vec3<T> &v) { x += v.x, y += v.y, z += v.z; return *this; } Vec3<T>& operator *= (const Vec3<T> &v) { x *= v.x, y *= v.y, z *= v.z; return *this; } Vec3<T> operator - () const { return Vec3<T>(-x, -y, -z); } T length2() const { return x * x + y * y + z * z; } T length() const { return sqrt(length2()); } friend std::ostream & operator << (std::ostream &os, const Vec3<T> &v) { os << "[" << v.x << " " << v.y << " " << v.z << "]"; return os; } }; typedef Vec3<float> Vec3f; class Sphere { public: Vec3f center; /// position of the sphere float radius, radius2; /// sphere radius and radius^2 Vec3f surfaceColor, emissionColor; /// surface color and emission (light) float transparency, reflection; /// surface transparency and reflectivity Sphere( const Vec3f &c, const float &r, const Vec3f &sc, const float &refl = 0, const float &transp = 0, const Vec3f &ec = 0) : center(c), radius(r), radius2(r * r), surfaceColor(sc), emissionColor(ec), transparency(transp), reflection(refl) { /* empty */ } //[comment] // Compute a ray-sphere intersection using the geometric solution //[/comment] bool intersect(const Vec3f &rayorig, const Vec3f &raydir, float &t0, float &t1) const { Vec3f l = center - rayorig; float tca = l.dot(raydir); if (tca < 0) return false; float d2 = l.dot(l) - tca * tca; if (d2 > radius2) return false; float thc = sqrt(radius2 - d2); t0 = tca - thc; t1 = tca + thc; return true; } }; //[comment] // This variable controls the maximum recursion depth //[/comment] #define MAX_RAY_DEPTH 5 float mix(const float &a, const float &b, const float &mix) { return b * mix + a * (1 - mix); } //[comment] // This is the main trace function. It takes a ray as argument (defined by its origin // and direction). We test if this ray intersects any of the geometry in the scene. // If the ray intersects an object, we compute the intersection point, the normal // at the intersection point, and shade this point using this information. // Shading depends on the surface property (is it transparent, reflective, diffuse). // The function returns a color for the ray. If the ray intersects an object that // is the color of the object at the intersection point, otherwise it returns // the background color. //[/comment] Vec3f trace( const Vec3f &rayorig, const Vec3f &raydir, const std::vector<Sphere> &spheres, const int &depth) { //if (raydir.length() != 1) std::cerr << "Error " << raydir << std::endl; float tnear = INFINITY; const Sphere* sphere = NULL; // find intersection of this ray with the sphere in the scene for (unsigned i = 0; i < spheres.size(); ++i) { float t0 = INFINITY, t1 = INFINITY; if (spheres[i].intersect(rayorig, raydir, t0, t1)) { if (t0 < 0) t0 = t1; if (t0 < tnear) { tnear = t0; sphere = &spheres[i]; } } } // if there's no intersection return black or background color if (!sphere) return Vec3f(2); Vec3f surfaceColor = 0; // color of the ray/surfaceof the object intersected by the ray Vec3f phit = rayorig + raydir * tnear; // point of intersection Vec3f nhit = phit - sphere->center; // normal at the intersection point nhit.normalize(); // normalize normal direction // If the normal and the view direction are not opposite to each other // reverse the normal direction. That also means we are inside the sphere so set // the inside bool to true. Finally reverse the sign of IdotN which we want // positive. float bias = 1e-4; // add some bias to the point from which we will be tracing bool inside = false; if (raydir.dot(nhit) > 0) nhit = -nhit, inside = true; if ((sphere->transparency > 0 || sphere->reflection > 0) && depth < MAX_RAY_DEPTH) { float facingratio = -raydir.dot(nhit); // change the mix value to tweak the effect float fresneleffect = mix(pow(1 - facingratio, 3), 1, 0.1); // compute reflection direction (not need to normalize because all vectors // are already normalized) Vec3f refldir = raydir - nhit * 2 * raydir.dot(nhit); refldir.normalize(); Vec3f reflection = trace(phit + nhit * bias, refldir, spheres, depth + 1); Vec3f refraction = 0; // if the sphere is also transparent compute refraction ray (transmission) if (sphere->transparency) { float ior = 1.1, eta = (inside) ? ior : 1 / ior; // are we inside or outside the surface? float cosi = -nhit.dot(raydir); float k = 1 - eta * eta * (1 - cosi * cosi); Vec3f refrdir = raydir * eta + nhit * (eta * cosi - sqrt(k)); refrdir.normalize(); refraction = trace(phit - nhit * bias, refrdir, spheres, depth + 1); } // the result is a mix of reflection and refraction (if the sphere is transparent) surfaceColor = ( reflection * fresneleffect + refraction * (1 - fresneleffect) * sphere->transparency) * sphere->surfaceColor; } else { // it's a diffuse object, no need to raytrace any further for (unsigned i = 0; i < spheres.size(); ++i) { if (spheres[i].emissionColor.x > 0) { // this is a light Vec3f transmission = 1; Vec3f lightDirection = spheres[i].center - phit; lightDirection.normalize(); for (unsigned j = 0; j < spheres.size(); ++j) { if (i != j) { float t0, t1; if (spheres[j].intersect(phit + nhit * bias, lightDirection, t0, t1)) { transmission = 0; break; } } } surfaceColor += sphere->surfaceColor * transmission * std::max(float(0), nhit.dot(lightDirection)) * spheres[i].emissionColor; } } } return surfaceColor + sphere->emissionColor; } //[comment] // Main rendering function. We compute a camera ray for each pixel of the image // trace it and return a color. If the ray hits a sphere, we return the color of the // sphere at the intersection point, else we return the background color. //[/comment] void render(const std::vector<Sphere> &spheres) { unsigned width = 640, height = 480; Vec3f *image = new Vec3f[width * height], *pixel = image; float invWidth = 1 / float(width), invHeight = 1 / float(height); float fov = 30, aspectratio = width / float(height); float angle = tan(M_PI * 0.5 * fov / 180.); // Trace rays for (unsigned y = 0; y < height; ++y) { for (unsigned x = 0; x < width; ++x, ++pixel) { float xx = (2 * ((x + 0.5) * invWidth) - 1) * angle * aspectratio; float yy = (1 - 2 * ((y + 0.5) * invHeight)) * angle; Vec3f raydir(xx, yy, -1); raydir.normalize(); *pixel = trace(Vec3f(0), raydir, spheres, 0); } } // Save result to a PPM image (keep these flags if you compile under Windows) std::ofstream ofs("./untitled.ppm", std::ios::out | std::ios::binary); ofs << "P6\n" << width << " " << height << "\n255\n"; for (unsigned i = 0; i < width * height; ++i) { ofs << (unsigned char)(std::min(float(1), image[i].x) * 255) << (unsigned char)(std::min(float(1), image[i].y) * 255) << (unsigned char)(std::min(float(1), image[i].z) * 255); } ofs.close(); delete [] image; } //[comment] // In the main function, we will create the scene which is composed of 5 spheres // and 1 light (which is also a sphere). Then, once the scene description is complete // we render that scene, by calling the render() function. //[/comment] int main(int argc, char **argv) { srand48(13); std::vector<Sphere> spheres; // position, radius, surface color, reflectivity, transparency, emission color spheres.push_back(Sphere(Vec3f( 0.0, -10004, -20), 10000, Vec3f(0.20, 0.20, 0.20), 0, 0.0)); spheres.push_back(Sphere(Vec3f( 0.0, 0, -20), 4, Vec3f(1.00, 0.32, 0.36), 1, 0.5)); spheres.push_back(Sphere(Vec3f( 5.0, -1, -15), 2, Vec3f(0.90, 0.76, 0.46), 1, 0.0)); spheres.push_back(Sphere(Vec3f( 5.0, 0, -25), 3, Vec3f(0.65, 0.77, 0.97), 1, 0.0)); spheres.push_back(Sphere(Vec3f(-5.5, 0, -15), 3, Vec3f(0.90, 0.90, 0.90), 1, 0.0)); // light spheres.push_back(Sphere(Vec3f( 0.0, 20, -30), 3, Vec3f(0.00, 0.00, 0.00), 0, 0.0, Vec3f(3))); render(spheres); return 0; }