D3D摄像机类和非摄像机类需要进行摄像机操作的思路

1.摄像机类的实现思想

摄像机类的实现，主要是因为D3DXMatrixLookAtLH()求取的是指定摄像机位置和观察坐标系向量的矩阵，但如果摄像机位置和观察坐标系向量是根据用户输入来确定的，那么D3DXMatrixLookAtLH显得力不从心。原因：

D3DXMATRIX* D3DXMatrixLookAtLH(  _Inout_       D3DXMATRIX  *pOut,  _In_    const D3DXVECTOR3 *pEye,  _In_    const D3DXVECTOR3 *pAt,  _In_    const D3DXVECTOR3 *pUp);

其中的pAt是观察的朝向，摄像机的z = (pAt - pEye).Normalize(), 摄像机的y = pUp, 摄像机的x= 摄像机z x 摄像机y再规范单位化。但是用户输入时候，很难从改变pAt位置来改变摄像机z。设置也很不直观，所以需要开发自己的摄像机类，特别是在飞行或者第一人称射击游戏中。

开发自己的摄像机类，主要思想是：定义摄像机的位置_pos，方向向量_look, _right, _up；主角可以在这些方向上进行移动摄像机的位置_pos(这些方向向量也是有自己的xyz的)，也可以绕这些方向进行旋转（旋转时候只针对某个轴进行旋转，然后对其它轴乘以该旋转矩阵进行变换)；从而可以简单的得到新的_pos,_look, _right, _up，将整个世界坐标系中的物体变换到观察坐标系中即可。因为模型坐标系转换到世界坐标系要进行RT,所以世界坐标系中旋转到视图坐标系（模型坐标系）中进行V = T-1R-1矩阵变换即可。这个变换也是

D3DXMatrixLookAtLH函数得到视图矩阵的方法， 这里只不过是使得输入移动和旋转更加直观。

2.非摄像机类需要用到摄像机效果的实现思路

如果不是第一人称类型的摄像机操作，而是RPG类型的飞行摄像机，不能输入位置和摄像机旋转，那么可以直接配置pos 位置。2D中通过D3DXMatrixOrthoLH函数的参数，放大传入的w、h可以实现模拟的远离缩小；拉动摄像机的y坐标就可以上升了。3D中设置固定的摄像机位置y值上下移动，z值可以设置近大远小效果，还是通过D3DXMatrixLookAtLH设置变换矩阵即可。

3.摄像机类实现代码及其注释

#ifndef __cameraH__#define __cameraH__#include <d3dx9.h>class Camera{public:enum CameraType { LANDOBJECT, AIRCRAFT };Camera();Camera(CameraType cameraType);~Camera();void strafe(float units); // left/rightvoid fly(float units);    // up/downvoid walk(float units);   // forward/backwardvoid pitch(float angle); // rotate on right vectorvoid yaw(float angle);   // rotate on up vectorvoid roll(float angle);  // rotate on look vectorvoid getViewMatrix(D3DXMATRIX* V); void setCameraType(CameraType cameraType); void getPosition(D3DXVECTOR3* pos); void setPosition(D3DXVECTOR3* pos); void getRight(D3DXVECTOR3* right);void getUp(D3DXVECTOR3* up);void getLook(D3DXVECTOR3* look);private:CameraType  _cameraType;D3DXVECTOR3 _right;D3DXVECTOR3 _up;D3DXVECTOR3 _look;D3DXVECTOR3 _pos;};#endif 

#include "camera.h"Camera::Camera(){_cameraType = AIRCRAFT;_pos   = D3DXVECTOR3(0.0f, 0.0f, 0.0f);_right = D3DXVECTOR3(1.0f, 0.0f, 0.0f);_up    = D3DXVECTOR3(0.0f, 1.0f, 0.0f);_look  = D3DXVECTOR3(0.0f, 0.0f, 1.0f);}Camera::Camera(CameraType cameraType){_cameraType = cameraType;_pos   = D3DXVECTOR3(0.0f, 0.0f, 0.0f);_right = D3DXVECTOR3(1.0f, 0.0f, 0.0f);_up    = D3DXVECTOR3(0.0f, 1.0f, 0.0f);_look  = D3DXVECTOR3(0.0f, 0.0f, 1.0f);}Camera::~Camera(){}void Camera::getPosition(D3DXVECTOR3* pos){*pos = _pos;}void Camera::setPosition(D3DXVECTOR3* pos){_pos = *pos;}void Camera::getRight(D3DXVECTOR3* right){*right = _right;}void Camera::getUp(D3DXVECTOR3* up){*up = _up;}void Camera::getLook(D3DXVECTOR3* look){*look = _look;}void Camera::walk(float units){// move only on xz plane for land object// 观察摄像机，在方向_look只能沿着xz（ 不一定是(0,0,1) )改变前行if( _cameraType == LANDOBJECT )_pos += D3DXVECTOR3(_look.x, 0.0f, _look.z) * units;if( _cameraType == AIRCRAFT )_pos += _look * units;}void Camera::strafe(float units){// move only on xz plane for land object// 观察摄像机，在方向_right只能沿着xz（ 不一定是(1,0,0) )改变前行if( _cameraType == LANDOBJECT )_pos += D3DXVECTOR3(_right.x, 0.0f, _right.z) * units;if( _cameraType == AIRCRAFT )_pos += _right * units;}void Camera::fly(float units){// move only on y-axis for land object// 观察摄像机，在_up方向上只能向上_pos.y移动if( _cameraType == LANDOBJECT )_pos.y += units;if( _cameraType == AIRCRAFT )_pos += _up * units;}void Camera::pitch(float angle){// 绕_right轴旋转，地面摄像机和空中摄像机都可以D3DXMATRIX T;D3DXMatrixRotationAxis(&T, &_right,angle);// rotate _up and _look around _right vector// 因为绕_right轴移动，所以_up需要进行T旋转D3DXVec3TransformCoord(&_up,&_up, &T);// _look轴需要进行T旋转D3DXVec3TransformCoord(&_look,&_look, &T);}void Camera::yaw(float angle){D3DXMATRIX T;// rotate around world y (0, 1, 0) always for land object// 地面摄像机不能做_up旋转,因为_up不一定是世界坐标系的y,所以只能做基于世界坐标系Y轴旋转if( _cameraType == LANDOBJECT )D3DXMatrixRotationY(&T, angle);// rotate around own up vector for aircraftif( _cameraType == AIRCRAFT )D3DXMatrixRotationAxis(&T, &_up, angle);// rotate _right and _look around _up or y-axisD3DXVec3TransformCoord(&_right,&_right, &T);D3DXVec3TransformCoord(&_look,&_look, &T);}void Camera::roll(float angle){// only roll for aircraft type// 地面观察摄像机，不能进行绕_look轴旋转，因为太怪异了if( _cameraType == AIRCRAFT ){D3DXMATRIX T;D3DXMatrixRotationAxis(&T, &_look,angle);// rotate _up and _right around _look vectorD3DXVec3TransformCoord(&_right,&_right, &T);D3DXVec3TransformCoord(&_up,&_up, &T);}}void Camera::getViewMatrix(D3DXMATRIX* V){// Keep camera's axes orthogonal to eachother// 摄像机的视图变换，本来是物体坐标系到世界坐标系中需要进行S*R*T变换（缩放，旋转，平移)// 现在是世界坐标系变换到物体坐标系（观察坐标系中）,也就是要进行T-1R-1S-1变换（逆向平移，逆向旋转，逆向缩放）// 因为这里没有缩放S所以进行T-1R-1变换就得到在视图坐标系描述世界坐标系中物体的位置。// 因为摄像机_look,_right,_up向量由于外部的位置移动和旋转，发生了改变，所以需要先规格化为单位向量，方便旋转D3DXVec3Normalize(&_look, &_look);// 由于_right,_look求得_up向量,认为D3DXVec3Cross(&_up, &_look, &_right);D3DXVec3Normalize(&_up, &_up);// 如果_right存在精度问题，那么认为_up是正确的，求取_right向量D3DXVec3Cross(&_right, &_up, &_look);D3DXVec3Normalize(&_right, &_right);// Build the view matrix:// V = T-1R-1平移部分，进行平移float x = -D3DXVec3Dot(&_right, &_pos);float y = -D3DXVec3Dot(&_up, &_pos);float z = -D3DXVec3Dot(&_look, &_pos);// V = T-1R-1旋转部分，R-1刚好是R的转置(*V)(0,0) = _right.x; (*V)(0, 1) = _up.x; (*V)(0, 2) = _look.x; (*V)(0, 3) = 0.0f;(*V)(1,0) = _right.y; (*V)(1, 1) = _up.y; (*V)(1, 2) = _look.y; (*V)(1, 3) = 0.0f;(*V)(2,0) = _right.z; (*V)(2, 1) = _up.z; (*V)(2, 2) = _look.z; (*V)(2, 3) = 0.0f;(*V)(3,0) = x;        (*V)(3, 1) = y;     (*V)(3, 2) = z;       (*V)(3, 3) = 1.0f;// 得到V后，就可以通过Device->SetTransform(D3DTS_VIEW, &V);就可以实现视图变换了}void Camera::setCameraType(CameraType cameraType){_cameraType = cameraType;}

调用：

#include "d3dUtility.h"#include "camera.h"//// Globals//IDirect3DDevice9* Device = 0; const int Width  = 640;const int Height = 480;Camera TheCamera(Camera::AIRCRAFT/*LANDOBJECT*/);//// Framework functions//bool Setup(){//// Setup a basic scene.  The scene will be created the// first time this function is called.//d3d::DrawBasicScene(Device, 0.0f); //// Set projection matrix.//D3DXMATRIX proj;D3DXMatrixPerspectiveFovLH(&proj,D3DX_PI * 0.25f, // 45 - degree(float)Width / (float)Height,1.0f,1000.0f);Device->SetTransform(D3DTS_PROJECTION, &proj);return true;}void Cleanup(){// pass 0 for the first parameter to instruct cleanup.d3d::DrawBasicScene(0, 0.0f);}bool Display(float timeDelta){if( Device ){//// Update: Update the camera.//if( ::GetAsyncKeyState('W') & 0x8000f )TheCamera.walk(4.0f * timeDelta);if( ::GetAsyncKeyState('S') & 0x8000f )TheCamera.walk(-4.0f * timeDelta);if( ::GetAsyncKeyState('A') & 0x8000f )TheCamera.strafe(-4.0f * timeDelta);if( ::GetAsyncKeyState('D') & 0x8000f )TheCamera.strafe(4.0f * timeDelta);if( ::GetAsyncKeyState('R') & 0x8000f )TheCamera.fly(4.0f * timeDelta);if( ::GetAsyncKeyState('F') & 0x8000f )TheCamera.fly(-4.0f * timeDelta);if( ::GetAsyncKeyState(VK_UP) & 0x8000f )TheCamera.pitch(1.0f * timeDelta);if( ::GetAsyncKeyState(VK_DOWN) & 0x8000f )TheCamera.pitch(-1.0f * timeDelta);if( ::GetAsyncKeyState(VK_LEFT) & 0x8000f )TheCamera.yaw(-1.0f * timeDelta);if( ::GetAsyncKeyState(VK_RIGHT) & 0x8000f )TheCamera.yaw(1.0f * timeDelta);if( ::GetAsyncKeyState('N') & 0x8000f )TheCamera.roll(1.0f * timeDelta);if( ::GetAsyncKeyState('M') & 0x8000f )TheCamera.roll(-1.0f * timeDelta);// Update the view matrix representing the cameras         // new position/orientation.D3DXMATRIX V;TheCamera.getViewMatrix(&V);//D3DXMatrixLookAtLH()Device->SetTransform(D3DTS_VIEW, &V);//// Render//Device->Clear(0, 0, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, 0x00000000, 1.0f, 0);Device->BeginScene();d3d::DrawBasicScene(Device, 1.0f);Device->EndScene();Device->Present(0, 0, 0, 0);}return true;}//// WndProc//LRESULT CALLBACK d3d::WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam){switch( msg ){case WM_DESTROY:::PostQuitMessage(0);break;case WM_KEYDOWN:if( wParam == VK_ESCAPE )::DestroyWindow(hwnd);break;}return ::DefWindowProc(hwnd, msg, wParam, lParam);}//// WinMain//int WINAPI WinMain(HINSTANCE hinstance,   HINSTANCE prevInstance,    PSTR cmdLine,   int showCmd){if(!d3d::InitD3D(hinstance,Width, Height, true, D3DDEVTYPE_HAL, &Device)){::MessageBox(0, "InitD3D() - FAILED", 0, 0);return 0;}if(!Setup()){::MessageBox(0, "Setup() - FAILED", 0, 0);return 0;}d3d::EnterMsgLoop( Display );Cleanup();Device->Release();return 0;}