关于DX中纹理平移的一个小问题

被群里的童鞋问到DX纹理平移的问题，开始实在没心思写，以为太简单了，最后他问了一天，出于好心答应帮他看下，结果看的时候花了我将近2个小时找出原因。贴个代码，以供以后参考！

#include "d3dUtility.h"#include <vector>#include "D3dx9math.h"#include <d3d9.h>#pragma   comment(lib, "d3d9.lib ")#pragma   comment(lib, "winmm.lib ")#pragma   comment(lib, "d3dx9.lib ")#pragma   comment(lib, "msvcrtd.lib ")//// Globals//IDirect3DDevice9* Device = 0; const int Width  = 640;const int Height = 480; ID3DXMesh*   Teapot = 0;D3DMATERIAL9 TeapotMtrl;IDirect3DVertexBuffer9* BkGndQuad = 0;IDirect3DTexture9*      CrateTex  = 0;IDirect3DTexture9*StrideTex=0;D3DMATERIAL9            BkGndMtrl;//// Classes and Structures//struct Vertex{Vertex(){}Vertex(float x, float y, float z,float nx, float ny, float nz,float u, float v){_x  = x;  _y  = y;  _z  = z;_nx = nx; _ny = ny; _nz = nz;_u  = u;  _v  = v;}    float _x, _y, _z;    float _nx, _ny, _nz;    float _u, _v; // texture coordinatesstatic const DWORD FVF;};const DWORD Vertex::FVF = D3DFVF_XYZ | D3DFVF_NORMAL | D3DFVF_TEX1;//// Framework Functions//bool Setup(){// // Init Materials//TeapotMtrl = d3d::RED_MTRL;TeapotMtrl.Diffuse.a = 0.5f; // set alpha to 50% opacityBkGndMtrl = d3d::GREEN_MTRL;//// Create the teapot.//D3DXCreateTeapot(Device, &Teapot, 0);//// Create the background quad.//Device->CreateVertexBuffer(6 * sizeof(Vertex), D3DUSAGE_WRITEONLY,Vertex::FVF,D3DPOOL_MANAGED,&BkGndQuad,0);Vertex* v;BkGndQuad->Lock(0, 0, (void**)&v, 0);v[0] = Vertex(-1.0f, -1.0f, 0.5f, 0.0f, 0.0f, -1.0f, 0.0f, 1.0f);v[1] = Vertex(-1.0f,  1.0f, 0.5f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f);v[2] = Vertex( 1.0f,  1.0f, 0.5f, 0.0f, 0.0f, -1.0f, 1.0f, 0.0f);v[3] = Vertex(-1.0f, -1.0f, 0.5f, 0.0f, 0.0f, -1.0f, 0.0f, 1.0f);v[4] = Vertex( 1.0f,  1.0f, 0.5f, 0.0f, 0.0f, -1.0f, 1.0f, 0.0f);v[5] = Vertex( 1.0f, -1.0f, 0.5f, 0.0f, 0.0f, -1.0f, 1.0f, 1.0f);BkGndQuad->Unlock();Device->SetRenderState(D3DRS_LIGHTING ,false);Device->SetRenderState(D3DRS_NORMALIZENORMALS, true);Device->SetRenderState(D3DRS_SPECULARENABLE, true);Device->SetSamplerState(0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);Device->SetSamplerState(0, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);Device->SetSamplerState(0, D3DSAMP_MIPFILTER, D3DTEXF_LINEAR);Device->SetSamplerState( 0, D3DSAMP_ADDRESSU, D3DTADDRESS_WRAP );Device->SetSamplerState( 0, D3DSAMP_ADDRESSV, D3DTADDRESS_WRAP );D3DXCreateTextureFromFile(Device,"crate.jpg",&CrateTex);D3DXVECTOR3 pos(0.0f, 0.0f, -3.0f);D3DXVECTOR3 target(0.0f, 0.0f, 0.0f);D3DXVECTOR3 up(0.0f, 1.0f, 0.0f);D3DXMATRIX V;D3DXMatrixLookAtLH(&V, &pos, &target, &up);Device->SetTransform(D3DTS_VIEW, &V);//// Set projection matrix.//D3DXMATRIX proj;D3DXMatrixPerspectiveFovLH(&proj,D3DX_PI * 0.5f, // 90 - degree(float)Width / (float)Height,1.0f,1000.0f);Device->SetTransform(D3DTS_PROJECTION, &proj);return true;}void Cleanup(){d3d::Release<IDirect3DVertexBuffer9*>(BkGndQuad);d3d::Release<ID3DXMesh*>(Teapot);d3d::Release<IDirect3DTexture9*>(CrateTex);}bool Display(float timeDelta){if( Device ){D3DXMATRIX mat_texture;Device->SetTextureStageState(0, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTFF_COUNT2);D3DXMatrixIdentity(&mat_texture);mat_texture._31 = 0.5;//这样写平移，因为二维的坐标(x,y)在变换时算成(x,y,1,0)与纹理变换矩阵相乘的//D3DXMatrixTranslation(&mat_texture, 0.5, 0, 0);//这样写不能平移HRESULT hr = Device->SetTransform(D3DTS_TEXTURE0, &mat_texture);Device->Clear(0, 0, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, 0x00000000, 1.0f, 0);Device->BeginScene();Device->SetFVF(Vertex::FVF);Device->SetStreamSource(0, BkGndQuad, 0, sizeof(Vertex));Device->SetTexture(0, CrateTex);Device->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 2);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;}