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来自借来的图书3D数学基础：图形与游戏开发。记录一下。

#ifndef VECTOR3_H_INCLUDED
#define VECTOR3_H_INCLUDED

class Vector3{

public:
    float x,y,z;
    Vector3() {}
    Vector3(){const Vector3 &a} : x(a.x),y(a.y),z(a.z) {}
    Vector3(float nx,float ny,float nz) : x(nx),y(ny),z(nz) {}


    Vector3 &operator =(const Vector3 &a){
        x = a.x;
        y = a.y;
        z = a.z;
    }


    bool operator ==(const Vector3 &a){
        return x == a.x && y == a.y && z == a.z;
    }

    bool operator !=(const Vector3 &a){
        return x != a.x || y != a.y || z != a.z;
    }

    void zero() {
        x = y = z = 0.0f;
    }

    Vector3 operator - () const {
    	return Vector3(-x,-y,-z);
    }

    Vector3 operator +(const Vector3 &a) const{
    	return Vector3(x + a.x, y + a.y, z + a.z);
    }

    Vector3 operator -(const Vector3 &a) const{
        return Vector3(x - a.x,y-a.y,z-a.z);
    }

    Vector3 operator *(float a ) const {
    	return Vector3(x * a, y * a, z * a);
    }

    Vector3 operator /(float a) const {
    	float oneOverA = 1.0f / a;
    	return Vector3(x*oneOverA,y*oneOverA,z*oneOverA);
    }

    Vector3 &operator +=(const Vector3 &a){
    	x += a.x;
    	y += a.y;
    	z += a.z;
    	return *this;
    }

    Vector3 &operator -=(const Vector3 &a){
    	x-= a.x;
    	y-= a.y;
    	z-= a.z;
    	return *this;
    }

    Vector &operator *=(Vector3 &a){
    	x *= a;
    	y *= a;
    	z *= a;
    	return *this;
    }

    Vector3 &operator /=(float a){
    	float oneOverA = 1.0f /a;
    	x *= oneOverA；
    	y *= oneOverA；
    	z *= oneOverA；
    	return *this;
    }

    void normalize(){
    	float magSq = x*x + y*y + z*z;
    	if(magSq > 0.0f){
    		float oneOverMag = 1.0f/sqrt(magSq);
    		x *= oneOverMag;
    		y *= oneOverMag;
    		z *= oneOverMag;
    	}
    }

    float operator * (const Vector3 &a){
    	return x * a.x + y * a.y + z * a.z;
    }
};

inline float vectorMag(const Vector3 &a){
	return sqrt(a.x * a.x , a.y * a.y, a.z * a.z);
}

inline Vector3 crossProduct(const Vector3 &a,const Vector3 &b){
	return Vector3(
		a.y * b.z - a.z * b.y,
		a.z * b.x - a.x * b.z;
		a.x * b.y - a.y * b.x;
		)
}

inline Vector3 operator * (float k,const Vector &v){
	return Vector3(k*v.x,k*v.y,k*v.z);
}

inline float distance(const Vector3 &a,const Vector &b){
	float dx = a.x - b.x;
	float dy = a.y - b.y;
	float dz = a.z - b.z;
	return sqrt(dx * dx,dy * dy,dz * dz);
}

extern const Vector3 kZeroVector;
#endif // VECTOR3_H_INCLUDED