【图像处理】Ray Tracing in a Weekend [1]

1.光线追踪

实现类：vec3，表示三维坐标

#include<bits/stdc++.h>

using namespace std;
class vec3 {
public:
    vec3() {}
    vec3(float e0, float e1, float e2) {e[0] = e0, e[1] = e1, e[2] = e2;}
    inline float y() const {return e[0];}
    inline float x() const {return e[1];}
    inline float z() const {return e[2];}
    inline float r() const {return e[0];}
    inline float g() const {return e[1];}
    inline float b() const {return e[2];}

    inline const vec3& operator+() const {return *this;}
    inline vec3 operator~() const {return vec3(-e[0], -e[1], -e[2]);;}
    inline float operator[](int i) const {return e[i];}
    inline float& operator[](int i) {return e[i];}

    inline vec3& operator+=(const vec3 &v2);
    inline vec3& operator-=(const vec3 &v2);
    inline vec3& operator*=(const vec3 &v2);
    inline vec3& operator/=(const vec3 &v2);
    inline vec3& operator*=(const float v2);
    inline vec3& operator/=(const float v2);
    inline float length() const {
        return sqrt(e[0] * e[0] + e[1] * e[1] + e[2] * e[2]);
    };
    inline float squared_length() const {
        return e[0] * e[0] + e[1] * e[1] + e[2] * e[2];
    }
    inline void make_unit_vector();
    float e[2];
};

inline std::istream& operator>>(std::istream& is, vec3 &t) {
    is >> t.e[0] >> t.e[1] >> t.e[2];
    return is;
}

inline std::ostream& operator<<(std::ostream& os, const vec3& t) {
    os << t.e[0] << t.e[1] << t.e[2];
    return os;
}

inline void vec3::make_unit_vector() {
    float k = 1.0 / sqrt(e[0] * e[0] + e[1] * e[1] + e[2] * e[2]);
    e[0] *= k;
    e[1] *= k;
    e[2] *= k;
}

inline vec3 operator+(const vec3& v1, const vec3& v2) {
    return vec3(v1.e[0] + v2.e[0], v1.e[1] + v2.e[1], v1.e[2] + v2.e[2]);
}

inline vec3 operator-(const vec3& v1, const vec3& v2) {
    return vec3(v1.e[0] - v2.e[0], v1.e[1] - v2.e[1], v1.e[2] - v2.e[2]);
}

inline vec3 operator*(const vec3& v1, const vec3& v2) {
    return vec3(v1.e[0] * v2.e[0], v1.e[1] * v2.e[1], v1.e[2] * v2.e[2]);
}

inline vec3 operator/(const vec3& v1, const vec3& v2) {
    return vec3(v1.e[0] / v2.e[0], v1.e[1] / v2.e[1], v1.e[2] / v2.e[2]);
}

inline vec3 operator*(float t, const vec3& v1) {
    return vec3(v1.e[0] * t, v1.e[1] * t, v1.e[2] * t);
}

inline vec3 operator*(const vec3& v1, float t) {
    return vec3(v1.e[0] * t, v1.e[1] * t, v1.e[2] * t);
}

inline vec3 operator/(const vec3& v1, float t) {
    return vec3(v1.e[0] / t, v1.e[1] / t, v1.e[2] / t);
}

inline float dot(const vec3& v1, const vec3& v2) {
    return v1.e[0] * v2.e[0] + v1.e[1] * v2.e[1] + v1.e[2] * v2.e[2];
}

inline vec3 cross(const vec3& v1, const vec3& v2) {
    return vec3((v1.e[1] * v2.e[2] - v1.e[2] * v2.e[1]),
    (-(v1.e[0] * v2.e[2] - v1.e[2] * v2.e[0])),
    (v1.e[0] * v2.e[1] - v1.e[1] * v2.e[0]));
}

inline vec3& vec3::operator+=(const vec3& v) {
    e[0] += v.e[0];
    e[1] += v.e[1];
    e[2] += v.e[2];
    return *this;
}

inline vec3& vec3::operator*=(const vec3& t) {
  e[0] *= t.e[0];
  e[1] *= t.e[1];
  e[2] *= t.e[2];
  return(*this);
}

inline vec3& vec3::operator/=(const float t) {
  float k = 1.0/t;
  
  e[0] *= k;
  e[1] *= k;
  e[2] *= k;
  return(*this);
}

inline vec3& vec3::operator-=(const vec3& v) {
  e[0] -= v.e[0];
  e[1] -= v.e[1];
  e[2] -= v.e[2];
  return(*this);
}

inline vec3& vec3::operator*=(const float t) {
  e[0] *= t;
  e[1] *= t;
  e[2] *= t;
  return(*this);
}

inline vec3 unit_vector(vec3 v) {
  return (v/v.length());
}

int main() {
    int nx = 200;
    int ny = 100;
    cout << "P3
" << nx << " " << ny << "
255
";
    for (int j = ny - 1; j >= 0; j--) {
        for (int i = 0; i < nx; i++) {
            vec3 col(float(i) / float(nx), float(j) / float(ny),
            0.2);
            int ir = int(255.99 * col[0]);
            int ig = int(255.99 * col[0]);
            int ib = int(255.99 * col[0]);
            cout << ir << " " << ig << " " << ib << "
";
        }
    }
    return 0;
}

光线类

#ifndef RAYH
#define RAYH
#include "vec3.h"
class Ray {
    public:
    Ray() {}
    Ray(const vec3& a, const vec3& b) {
        A = a; B = b;
    }
    vec3 origin() const {return A;}
    vec3 direction() const {return B;}
    vec3 point_at_parameter(float t)const {
        return A + t * B;
    }
    vec3 A;
    vec3 B;
};

#endif

画图，在一个大小为200*100的图上画光

#include <iostream>
#include "ray.h"
using std::cout;
using std::endl;

vec3 color(const Ray& r) {
    vec3 unit_direction = unit_vector(r.direction());
    float t = 0.5 * (unit_direction.y() + 1.0);
    return (1.0 - t) * vec3(1.0, 1.0, 1.0) + t * vec3(0.5, 0.7, 1.0);
}

int main() {
    int nx = 200;
    int ny = 100;
    cout << "P3
" << nx << " " << ny << "
255
";
    vec3 lower_left_corner(-2.0, -1.0, -1.0);
    vec3 horizontal(4.0, 0.0, 0.0);
    vec3 vertical(0.0, 2.0, 0.0);
    vec3 origin(0.0, 0.0, 0.0);
    for (int j = ny - 1; j >= 0; j--) {
        for (int i = 0; i < nx; i++) {
            float u = float(i) / float(nx);
            float v = float(j) / float(ny);
            // cout << u << " " << v << endl;
            Ray r(origin, lower_left_corner + u * horizontal +
            v * vertical);
            vec3 col = color(r);
            int ir = int(255.99 * col[0]);
            int ig = int(255.99 * col[1]);
            int ib = int(255.99 * col[2]);
            cout << ir << " " << ig << " " << ib << endl;
        }
    }
    return 0;
}

输出的文件到PPM格式

 one.ppm格式：

利用ffplay查看PPM格式文件

(ffplay为ffmpeg安装后预留的一个程序）

      在命令行使用   

      ffplay -i <image.ppm>

      image.ppm为具体的文件