D3D中的向量

DD33DD中的向量 

D3DXVECTOR3

DD33DDXXVVEECCTTOORR33表示三维向量； 

* 

**向量相等 

1.通过“==”来判断向量是否相等，具体如下： 

D3DXVECTOR3   U(1.0F,0.0F,1.0F); 

D3DXVECTOR3   v(0.0F,1.0F,0.0F); 

If（u==v）returntrue； 

If（u！=v）returnfalse； 

2.判断浮点时应该定义一个“EPSILON”变量，如果两个浮点之间的差距小于 

EPSILON就认为两个浮点数相等，具体如下： 

constfloat  EPSILON =0.001f; 

15

bool  Equals(float  1hs,float rhs) 

{ 

Return  fabs(1hs - rhs)<EPSILON; 

}//完全不用在意这些事，因为D3DXVECTOR3的重载运算符已经完成了这些

功能 

*D3D 

**DD33DD向量模的计算 

表示向量长度： 

FLOAT   D3DXVec3Length 

( 

CONSTD3DXVECTOR3  *PV            //需要求模的向量 

) 

例： 

D3DVECTOR3   v(1.0f,2.0f,3.0f); 

Float magnitude = D3DXVec3Length（&v）；

* 

**向量规格化 

D3DXVECTOR3 *WINAPI  D3DXVec3Normalize( 

D3DXVECTOR3  *pOut,                  //输出单位向量 

CONSTD3DXVECTOR3  *pV               //输入的向量 

); 

* 

**向量加法 

D3DVECTOR3   U(2.0F,0.0F,1.0F); 

D3DVECTOR3   V(0.0F,-1.0F,5.0F); 

D3DVECTOR3   SUM = U + V; 

* 

**向量减法 

D3DVECTOR3   U(2.0F,0.0F,1.0F); 

D3DVECTOR3   V(0.0F,-1.0F,5.0F); 

D3DVECTOR3   SUM = U - V; 

* 

**数乘 

D3DVECTOR3   U(2.0F,0.0F,1.0F); 

D3DVECTOR3   scaledVec = U *10.0f; 

* 

**点乘 

FLOAT  D3DXVec3Dot（ 

CONSTD3DVECTOR3   *PV1; 

CONSTD3DVECTOR3   *PV2; 

） 

例: 

D3DVECTOR3   U(2.0F,0.0F,1.0F); 

D3DVECTOR3   V(0.0F,-1.0F,5.0F); 

                                 

float dot =  D3DXVec3Dot(&u,&v);