Tiny KABOOM first commit; the simplest possible ray marching

Author: ssloy

CMakeLists.txt

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+cmake_minimum_required (VERSION 2.8)
+project (tinykaboom)
+
+include(CheckCXXCompilerFlag)
+
+function(enable_cxx_compiler_flag_if_supported flag)
+    string(FIND "${CMAKE_CXX_FLAGS}" "${flag}" flag_already_set)
+    if(flag_already_set EQUAL -1)
+        check_cxx_compiler_flag("${flag}" flag_supported)
+        if(flag_supported)
+            set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${flag}" PARENT_SCOPE)
+        endif()
+        unset(flag_supported CACHE)
+    endif()
+endfunction()
+
+enable_cxx_compiler_flag_if_supported("-Wall")
+enable_cxx_compiler_flag_if_supported("-Wextra")
+enable_cxx_compiler_flag_if_supported("-pedantic")
+enable_cxx_compiler_flag_if_supported("-std=c++11")
+enable_cxx_compiler_flag_if_supported("-O3")
+enable_cxx_compiler_flag_if_supported("-fopenmp")
+
+file(GLOB SOURCES *.h *.cpp)
+
+add_executable(${PROJECT_NAME} ${SOURCES})
+

Readme.md

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+# Tiny KABOOM in less than 200 lines of bare C++
+
+This repository is a support code for my computer graphics lectures. It is not meant to be the ultimate rendering code or even physically realistic. It is meant to be **simple**. This project is distributed under the [DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE](https://en.wikipedia.org/wiki/WTFPL).
+
+**Check [the article](https://github.com/ssloy/tinykaboom/wiki) that accompanies the source code.
+If you are looking for a software rasterizer, check the [other part of the lectures](https://github.com/ssloy/tinyrenderer/wiki).**
+
+In my lectures I tend to avoid third party libraries as long as it is reasonable, because it forces to understand what is happening under the hood. So, the raytracing 256 lines of plain C++ give us this result:
+![](https://raw.githubusercontent.com/ssloy/tinykaboom/master/out.jpg)
+
+## compilation
+```sh
+git clone https://github.com/ssloy/tinykaboom.git
+cd tinykaboom
+mkdir build
+cd build
+cmake ..
+make
+```
+
+

geometry.h

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+#ifndef __GEOMETRY_H__
+#define __GEOMETRY_H__
+#include <cmath>
+#include <cassert>
+
+template <size_t DIM, typename T> struct vec {
+    vec() { for (size_t i=DIM; i--; data_[i] = T()); }
+          T& operator[](const size_t i)       { assert(i<DIM); return data_[i]; }
+    const T& operator[](const size_t i) const { assert(i<DIM); return data_[i]; }
+private:
+    T data_[DIM];
+};
+
+template <typename T> struct vec<3,T> {
+    vec() : x(T()), y(T()), z(T()) {}
+    vec(T X, T Y, T Z) : x(X), y(Y), z(Z) {}
+          T& operator[](const size_t i)       { assert(i<3); return i<=0 ? x : (1==i ? y : z); }
+    const T& operator[](const size_t i) const { assert(i<3); return i<=0 ? x : (1==i ? y : z); }
+    float norm() const { return std::sqrt(x*x+y*y+z*z); }
+    vec<3,T> & normalize(T l=1) { *this = (*this)*(l/norm()); return *this; }
+    T x,y,z;
+};
+
+template<size_t DIM,typename T> T operator*(const vec<DIM,T>& lhs, const vec<DIM,T>& rhs) {
+    T ret = T();
+    for (size_t i=DIM; i--; ret+=lhs[i]*rhs[i]);
+    return ret;
+}
+
+template<size_t DIM,typename T>vec<DIM,T> operator+(vec<DIM,T> lhs, const vec<DIM,T>& rhs) {
+    for (size_t i=DIM; i--; lhs[i]+=rhs[i]);
+    return lhs;
+}
+
+template<size_t DIM,typename T>vec<DIM,T> operator-(vec<DIM,T> lhs, const vec<DIM,T>& rhs) {
+    for (size_t i=DIM; i--; lhs[i]-=rhs[i]);
+    return lhs;
+}
+
+template<size_t DIM,typename T,typename U> vec<DIM,T> operator*(const vec<DIM,T> &lhs, const U& rhs) {
+    vec<DIM,T> ret;
+    for (size_t i=DIM; i--; ret[i]=lhs[i]*rhs);
+    return ret;
+}
+
+template<size_t DIM,typename T> vec<DIM,T> operator-(const vec<DIM,T> &lhs) {
+    return lhs*T(-1);
+}
+
+typedef vec<3, float> Vec3f;
+
+#endif //__GEOMETRY_H__
+

out.jpg

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+#define _USE_MATH_DEFINES
+#include <cmath>
+#include <algorithm>
+#include <limits>
+#include <iostream>
+#include <fstream>
+#include <vector>
+#include "geometry.h"
+
+const float sphere_radius   = 1.5;
+
+float signed_distance(const Vec3f &p) {
+    return p.norm() - sphere_radius;
+}
+
+bool sphere_trace(const Vec3f &orig, const Vec3f &dir, Vec3f &pos) {
+    pos = orig;
+    for (size_t i=0; i<128; i++) {
+        float d = signed_distance(pos);
+        if (d < 0) return true;
+        pos = pos + dir*std::max(d*0.1f, .01f);
+    }
+    return false;
+}
+
+int main() {
+    const int   width    = 640;
+    const int   height   = 480;
+    const float fov      = M_PI/3.;
+    std::vector<Vec3f> framebuffer(width*height);
+
+#pragma omp parallel for
+    for (size_t j = 0; j<height; j++) { // actual rendering loop
+        for (size_t i = 0; i<width; i++) {
+            float dir_x =  (i + 0.5) -  width/2.;
+            float dir_y = -(j + 0.5) + height/2.;    // this flips the image at the same time
+            float dir_z = -height/(2.*tan(fov/2.));
+            Vec3f hit;
+            if (sphere_trace(Vec3f(0, 0, 3), Vec3f(dir_x, dir_y, dir_z).normalize(), hit)) { // the camera is placed to (0,0,3) and it looks along the -z axis
+                framebuffer[i+j*width] = Vec3f(1, 1, 1);
+            } else {
+                framebuffer[i+j*width] = Vec3f(0.2, 0.7, 0.8); // background color
+            }
+        }
+    }
+
+    std::ofstream ofs("./out.ppm", std::ios::binary); // save the framebuffer to file
+    ofs << "P6\n" << width << " " << height << "\n255\n";
+    for (size_t i = 0; i < height*width; ++i) {
+        for (size_t j = 0; j<3; j++) {
+            ofs << (char)(std::max(0, std::min(255, static_cast<int>(255*framebuffer[i][j]))));
+        }
+    }
+    ofs.close();
+
+    return 0;
+}
+