最近的游戏引擎已经有个大概的样子了。不过还有许多东西要修改、添加。比如：粒子系统，总是感觉渲染的有点不对头，但就是看不出来。再看看吧～
以下是ZVector的头文件ZVector.h
1 #ifndef _ZVector_H_
2#define _ZVector_H_
3
4#include <cmath>
5
6#pragma pack(16) // 16 byte data align
7
8#define SIMD
9
10#ifndef SIMD
11#define SSE
12#endif
13
14#define PI (3.14159265359f)
15#define DEG2RAD(a) (PI/180*(a))
16#define RAD2DEG(a) (180/PI*(a))
17
18//##ModelId=46286C6102A1
19typedef float SCALAR;
20
21__declspec(align(16)) class ZVector
22   {
23 public:
24 SCALAR x;
25 SCALAR y;
26 SCALAR z; // x,y,z coordinates
27 SCALAR w;
28
29public:
30  /**//*** constructors ***/
31 ZVector(SCALAR a = 0.0f, SCALAR b = 0.0f, SCALAR c = 0.0f, SCALAR d = 1.0f) : x(a), y(b), z(c), w(d) {}
32 ZVector(const ZVector &vec) : x(vec.x), y(vec.y), z(vec.z), w(vec.w) {}
33
34 /**//*** menber functions ***/
35 void Null(void); // clears vector to (0, 0, 0, 1)
36 void Normalize(); // normalize this vector
37 void Negate(void); // invert the vector
38 const SCALAR Length() const; // length of vector
39 const ZVector CrossProduct(const ZVector &vec) const; // cross product
40 const SCALAR DotProduct(const ZVector &vec) const; // dot product
41 const ZVector UnitVector() const; // return the unit vector
42 const float Angle(const ZVector &normal) const; // return angle between two vectors
43 const ZVector Reflection(const ZVector& normal) const; // reflect this vector off surface with normal vector
44 const ZVector Rotate(const float angle,
45 const ZVector &normal) const; // rotate angle degrees about a normal
46
47 /**//*** operator overloading ***/
48 SCALAR & operator [](const long idx); // vector index
49 const ZVector & operator =(const ZVector &vec); // vector assignment
50 const bool operator ==(const ZVector &vec) const; // vecector equality
51 const bool operator !=(const ZVector &vec) const; // vecector inequality
52 const ZVector operator +(const ZVector &vec) const; // vector add
53 const ZVector operator +() const; // vector add (opposite of negation)
54 const ZVector & operator +=(const ZVector &vec); // vector increment
55 const ZVector operator -(const ZVector &vec) const; // vector subtraction
56 const ZVector operator -() const; // vector negation
57 const ZVector & operator -=(const ZVector& vec); // vector decrement
58 const ZVector & operator *=(const SCALAR &s); // SCALAR self-multiply
59 const ZVector & operator /=(const SCALAR &s); // SCALAR self-divecide
60 const ZVector operator *(const SCALAR &s) const; // post multiply by SCALAR
61 const ZVector operator *(const ZVector& vec) const; // multiply by ZVector
62 const ZVector operator /(SCALAR s) const; // divide by SCALAR
63 const ZVector operator ^(const ZVector &vec) const; // cross product
64 const SCALAR operator %(const ZVector &vec) const; // dot product
65 const SCALAR operator !() const;
66 const ZVector operator |(const SCALAR length) const; // return vector with specified length
67 const ZVector& operator |=(const float length); // set length of vector equal to length
68
69 /**//*** friends ***/
70 friend inline const ZVector operator*(const SCALAR &s, const ZVector &vec); // pre multiply by SCALAR
71 //friend inline const ZVector operator*(const ZVector &vec, const SCALAR &s); // post multiply by SCALAR
72 };
73
74#endif //_ZVector_H_
以下是实现部分ZVector.cpp的某个函数代码：
1// post multiply by SCALAR
2const ZVector ZVector::operator *(const SCALAR &s) const
3{
4 __declspec(align(16)) ZVector res;
5#ifdef SIMD
6 __asm
7 {
8 mov esi, s
9 movss xmm0, [esi] // xmm1[0] = s
10 shufps xmm0, xmm0, 0 // xmm1[1, 2, 3] = xmm1[0]
11 mov edi, this
12 mulps xmm0, [edi]
13 movaps res, xmm0
14 }
15#else
16#ifdef SSE
17 __m128 ms = _mm_set_ps1(s); // ms[0, 1, 2, 3] = s
18 *(__m128*)&res = _mm_mul_ps(*(__m128*)(this), ms);
19#else
20 res.x = x * s; res.y = y * s; res.z = z * s; res.w = w * s;
21#endif
22#endif
23 return res;
24}
每个函数都使用了SIMD汇编代码和SSE指令集的函数来进行CPU上的优化。效率非常高，SSE的效率一般比CPP的要高400%左右，而SIMD的效率一般比CPP的高550%左右。我使用了QueryPerformanceCounter、QueryPerformanceFrequency来获得精度非常高的计算机时间，经过对比得出上面的结果。
这次优化，有了很多心得，虽然觉得汇编实在恶心，但是还是有很多收获。还有SSE，让我更加了解了CPU计算原来可以这样高效。
最后要说的是：一定要让数据保证16位对齐，否则。。。。大家自己研究吧～
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