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Ray Tracing in One Weekend Summary II - vec3 class

向量类 vec3.h

我们构造的向量类如下

#include <iostream>
#include <cmath>
#include <cstdlib>

class vec3 {
public:
    vec3() {}
    vec3(float e0, float e1, float e2) { e[0] = e0; e[1] = e1; e[2] = e2; }
    inline float x() const { return e[0]; }
    inline float y() 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 t);
    inline vec3& operator/=(const float t);

    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[3];
};

类成员函数的实例化

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

inline vec3 operator*(const vec3 &v, float t) {
    return vec3(t*v.e[0], t*v.e[1], t*v.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/(vec3 v, float t) {
    return vec3(v.e[0]/t, v.e[1]/t, v.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[2] * v2.e[0] - v1.e[0] * v2.e[2],
                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& v) {
    e[0] -= v.e[0];
    e[1] -= v.e[1];
    e[2] -= v.e[2];
    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& 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) {
    float k = 1.0/t;

    e[0] *= k;
    e[1] *= k;
    e[2] *= k;
    return *this;
}

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

vec3类中的成员变量e[3]可以表示三维空间中的xyz坐标和rgb三个通道

类中成员函数有向量长度length,长度平方squared_length,单位化make_unit_vector


我们更改main函数中的代码来测试一下

#include "svpng.inc"
#include "vec3.h"
int main() {

    int nx=200,ny=150; // width & height
    unsigned char rgb[nx * ny * 3], *p = rgb;
    FILE *fp = fopen("rgb.png", "wb");
    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);
            *p++ = int(255.99*col[0]);    /* R */
            *p++ = int(255.99*col[1]);    /* G */
            *p++ = int(255.99*col[2]);    /* B */
        }

    svpng(fp, nx, ny, rgb, 0);
    fclose(fp); 
    return 0;
}

会得到与上一章相同的图像

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