首先看下數學公式：
由上面的數學公式，我們轉換的C++函數：
[cpp]
//-----------------------------------------------------------------------------
// Name: setupRotate()
// Desc: 繞x,y,z軸旋轉,axis:1表示繞x軸，2表示y軸，3表示z軸
//-----------------------------------------------------------------------------
VOID setupRotate(D3DXMATRIXA16 *returnMatrix,int axis, float theta)
{ www.2cto.com
float s, c;
s = sin(theta),c=cos(theta);
switch (axis) {
case 1: // Rotate about the x-axis
returnMatrix->_11 = 1.0f; returnMatrix->_12 = 0.0f; returnMatrix->_13 = 0.0f; returnMatrix->_14 = 0.0f;
returnMatrix->_21 = 0.0f; returnMatrix->_22 = c; returnMatrix->_23 = s; returnMatrix->_24 = 0.0f;
returnMatrix->_31 = 0.0f; returnMatrix->_32 = -s; returnMatrix->_33 = c; returnMatrix->_34 = 0.0f;
returnMatrix->_41 = 0.0f; returnMatrix->_42 = 0.0f; returnMatrix->_43 = 0.0f; returnMatrix->_44 = 1.0f;
break;
case 2: // Rotate about the y-axis
returnMatrix->_11 = c; returnMatrix->_12 = 0.0f; returnMatrix->_13 = -s; returnMatrix->_14 = 0.0f;
returnMatrix->_21 = 0.0f; returnMatrix->_22 = 1.0f; returnMatrix->_23 = 0.0f; returnMatrix->_24 = 0.0f;
returnMatrix->_31 = s; returnMatrix->_32 = 0.0f; returnMatrix->_33 = c; returnMatrix->_34 = 0.0f;
returnMatrix->_41 = 0.0f; returnMatrix->_42 = 0.0f; returnMatrix->_43 = 0.0f; returnMatrix->_44 = 1.0f;
break;
case 3: // Rotate about the z-axis
returnMatrix->_11 = c; returnMatrix->_12 = s; returnMatrix->_13 = 0.0f; returnMatrix->_14 = 0.0f;
returnMatrix->_21 = -s; returnMatrix->_22 = c; returnMatrix->_23 = 0.0f; returnMatrix->_24 = 0.0f;
returnMatrix->_31 = 0.0f; returnMatrix->_32 = 0.0f; returnMatrix->_33 = 1.0f; returnMatrix->_34 = 0.0f;
returnMatrix->_41 = 0.0f; returnMatrix->_42 = 0.0f; returnMatrix->_43 = 0.0f; returnMatrix->_44 = 1.0f;
break;
default:
// bogus axis index
assert(false);
}
}
//-----------------------------------------------------------------------------
// Name: setupRotate()
// Desc: 繞自定義軸旋轉
//-----------------------------------------------------------------------------
VOID setupRotate(const D3DXVECTOR3 &axis, D3DXMATRIXA16 *returnMatrix, float theta)
{
//要旋轉的向量軸必須是單位向量，不然物體會變形
//assert(fabs(axis*axis - 1.0f) < .01f);
float s, c;
s = sin(theta),c=cos(theta);
// 計算出一些重復利用的子表達式。
float a = 1.0f - c;
float ax = a * axis.x;
float ay = a * axis.y;
float az = a * axis.z;
returnMatrix->_11 = ax*axis.x + c;
returnMatrix->_12 = ax*axis.y + axis.z*s;
returnMatrix->_13 = ax*axis.z - axis.y*s;
returnMatrix->_14 = 0.0f;
returnMatrix->_21 = ay*axis.x - axis.z*s;
returnMatrix->_22 = ay*axis.y + c;
returnMatrix->_23 = ay*axis.z + axis.x*s;
returnMatrix->_24 = 0.0f;
returnMatrix->_31 = az*axis.x + axis.y*s;
returnMatrix->_32 = az*axis.y - axis.x*s;
returnMatrix->_33 = az*axis.z + c;
returnMatrix->_34 = 0.0f;
returnMatrix->_41 = 0.0f;
returnMatrix->_42 = 0.0f;
returnMatrix->_43 = 0.0f;
returnMatrix->_44 = 1.0f;
}
可能會有人對上面函數中的D3DXMATRIXA16和D3DXVECTOR3不理解，他們其實是Direct3D中表示4維矩陣和3維向量的結構體，可是我們數學公式裡涉及到的是3維矩陣，可以看下下面的轉換，因為要設計到矩陣相乘，故只能4維矩陣跟4維矩陣相乘，故把3維的轉換成4維的了。
具體使用上面兩個函數的例子：
[cpp]
// 旋轉
D3DXMATRIXA16 matWorld;
//自定義旋轉的軸
D3DXVECTOR3 axis(1.0f/sqrt(3), 1.0f/sqrt(3), 1.0f/sqrt(3));
D3DXMatrixIdentity( &matWorld );
/*DirectX 官方API*/
//D3DXMatrixRotationY( &matWorld, timeGetTime()/500.0f );
/*使用自定義旋轉函數1*/
//setupRotate(&matWorld,2,timeGetTime()/500.0f);
/*使用自定義旋轉函數2*/
setupRotate(axis,&matWorld,timeGetTime()/500.0f);
g_pd3dDevice->SetTransform( D3DTS_WORLD, &matWorld );
旋轉效果：
我稍微修改了下自定義旋轉的軸，改成一個非單位向量，(1.0f, 1.0f, 0.0f)，旋轉效果(變形的飛起，哈哈)：
完整代碼(看的麻煩的同學，可以拉到底下載整個項目來看)：
[cpp]
//-----------------------------------------------------------------------------
// File: Lights.cpp
// Copyright (c) Microsoft Corporation & Waitingfy.com. All rights reserved.
//-----------------------------------------------------------------------------
#include <Windows.h>
#include <mmsystem.h>
#include <d3dx9.h>
#include <strsafe.h>
#include <math.h>
#include <assert.h>
//-----------------------------------------------------------------------------
// Global variables
//-----------------------------------------------------------------------------
LPDIRECT3D9 g_pD3D = NULL; // Used to create the D3DDevice
LPDIRECT3DDEVICE9 g_pd3dDevice = NULL; // Our rendering device
LPDIRECT3DVERTEXBUFFER9 g_pVB = NULL; // Buffer to hold vertices
ID3DXMesh* Objects;//茶壺
// A structure for our custom vertex type. We added a normal, and omitted the
// color (which is provided by the material)
struct CUSTOMVERTEX
{
D3DXVECTOR3 position; // The 3D position for the vertex
D3DXVECTOR3 normal; // The surface normal for the vertex
};
// Our custom FVF, which describes our custom vertex structure
#define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZ|D3DFVF_NORMAL)
//-----------------------------------------------------------------------------
// Name: InitD3D()
// Desc: Initializes Direct3D
//-----------------------------------------------------------------------------
HRESULT InitD3D( HWND hWnd )
{
// Create the D3D object.
if( NULL == ( g_pD3D = Direct3DCreate9( D3D_SDK_VERSION ) ) )
return E_FAIL;
// Set up the structure used to create the D3DDevice. Since we are now
// using more complex geometry, we will create a device with a zbuffer.
D3DPRESENT_PARAMETERS d3dpp;
ZeroMemory( &d3dpp, sizeof(d3dpp) );
d3dpp.Windowed = TRUE;
d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
d3dpp.BackBufferFormat = D3DFMT_UNKNOWN;
d3dpp.EnableAutoDepthStencil = TRUE;
d3dpp.AutoDepthStencilFormat = D3DFMT_D16;
// Create the D3DDevice
if( FAILED( g_pD3D->CreateDevice( D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hWnd,
D3DCREATE_SOFTWARE_VERTEXPROCESSING,
&d3dpp, &g_pd3dDevice ) ) )
{
return E_FAIL;
}
// Turn off culling
g_pd3dDevice->SetRenderState( D3DRS_CULLMODE, D3DCULL_NONE );
// Turn on the zbuffer
g_pd3dDevice->SetRenderState( D3DRS_ZENABLE, TRUE );
return S_OK;
}
//-----------------------------------------------------------------------------
// Name: Cleanup()
// Desc: Releases all previously initialized objects
//-----------------------------------------------------------------------------
VOID Cleanup()
{
if( g_pVB != NULL )
g_pVB->Release();
if( g_pd3dDevice != NULL )
g_pd3dDevice->Release();
if( g_pD3D != NULL )
g_pD3D->Release();
if(Objects != NULL)
Objects->Release();
}
//-----------------------------------------------------------------------------
// Name: setupRotate()
// Desc: 繞x,y,z軸旋轉,axis:1表示繞x軸，2表示y軸，3表示z軸
//-----------------------------------------------------------------------------
VOID setupRotate(D3DXMATRIXA16 *returnMatrix,int axis, float theta)
{
float s, c;
s = sin(theta),c=cos(theta);
switch (axis) {
case 1: // Rotate about the x-axis
returnMatrix->_11 = 1.0f; returnMatrix->_12 = 0.0f; returnMatrix->_13 = 0.0f; returnMatrix->_14 = 0.0f;
returnMatrix->_21 = 0.0f; returnMatrix->_22 = c; returnMatrix->_23 = s; returnMatrix->_24 = 0.0f;
returnMatrix->_31 = 0.0f; returnMatrix->_32 = -s; returnMatrix->_33 = c; returnMatrix->_34 = 0.0f;
returnMatrix->_41 = 0.0f; returnMatrix->_42 = 0.0f; returnMatrix->_43 = 0.0f; returnMatrix->_44 = 1.0f;
break;
case 2: // Rotate about the y-axis
returnMatrix->_11 = c; returnMatrix->_12 = 0.0f; returnMatrix->_13 = -s; returnMatrix->_14 = 0.0f;
returnMatrix->_21 = 0.0f; returnMatrix->_22 = 1.0f; returnMatrix->_23 = 0.0f; returnMatrix->_24 = 0.0f;
returnMatrix->_31 = s; returnMatrix->_32 = 0.0f; returnMatrix->_33 = c; returnMatrix->_34 = 0.0f;
returnMatrix->_41 = 0.0f; returnMatrix->_42 = 0.0f; returnMatrix->_43 = 0.0f; returnMatrix->_44 = 1.0f;
break;
case 3: // Rotate about the z-axis
returnMatrix->_11 = c; returnMatrix->_12 = s; returnMatrix->_13 = 0.0f; returnMatrix->_14 = 0.0f;
returnMatrix->_21 = -s; returnMatrix->_22 = c; returnMatrix->_23 = 0.0f; returnMatrix->_24 = 0.0f;
returnMatrix->_31 = 0.0f; returnMatrix->_32 = 0.0f; returnMatrix->_33 = 1.0f; returnMatrix->_34 = 0.0f;
returnMatrix->_41 = 0.0f; returnMatrix->_42 = 0.0f; returnMatrix->_43 = 0.0f; returnMatrix->_44 = 1.0f;
break;
default:
// bogus axis index
assert(false);
}
}
//-----------------------------------------------------------------------------
// Name: setupRotate()
// Desc: 繞自定義軸旋轉,類似DirectX中的函數D3DXMatrixRotationAxis
//-----------------------------------------------------------------------------
VOID setupRotate(const D3DXVECTOR3 &axis, D3DXMATRIXA16 *returnMatrix, float theta)
{
//要旋轉的向量軸必須是單位向量，不然物體會變形
//assert(fabs(axis*axis - 1.0f) < .01f);
float s, c;
s = sin(theta),c=cos(theta);
// 計算出一些重復利用的子表達式。
float a = 1.0f - c;
float ax = a * axis.x;
float ay = a * axis.y;
float az = a * axis.z;
returnMatrix->_11 = ax*axis.x + c;
returnMatrix->_12 = ax*axis.y + axis.z*s;
returnMatrix->_13 = ax*axis.z - axis.y*s;
returnMatrix->_14 = 0.0f;
returnMatrix->_21 = ay*axis.x - axis.z*s;
returnMatrix->_22 = ay*axis.y + c;
returnMatrix->_23 = ay*axis.z + axis.x*s;
returnMatrix->_24 = 0.0f;
returnMatrix->_31 = az*axis.x + axis.y*s;
returnMatrix->_32 = az*axis.y - axis.x*s;
returnMatrix->_33 = az*axis.z + c;
returnMatrix->_34 = 0.0f;
returnMatrix->_41 = 0.0f;
returnMatrix->_42 = 0.0f;
returnMatrix->_43 = 0.0f;
returnMatrix->_44 = 1.0f;
}
//-----------------------------------------------------------------------------
// Name: SetupMatrices()
// Desc: Sets up the world, view, and projection transform matrices.
//-----------------------------------------------------------------------------
VOID SetupMatrices()
{
// 旋轉
D3DXMATRIXA16 matWorld;
//自定義旋轉的軸
//D3DXVECTOR3 axis(1.0f/sqrt(3), 1.0f/sqrt(3), 1.0f/sqrt(3));
D3DXVECTOR3 axis(1.0f, 1.0f, 0.0f);
D3DXMatrixIdentity( &matWorld );
/*DirectX 官方API*/
//D3DXMatrixRotationY( &matWorld, timeGetTime()/500.0f );
/*使用自定義旋轉函數1*/
//setupRotate(&matWorld,2,timeGetTime()/500.0f);
/*使用自定義旋轉函數2*/
setupRotate(axis,&matWorld,timeGetTime()/500.0f);
g_pd3dDevice->SetTransform( D3DTS_WORLD, &matWorld );
// 攝像機的位置
D3DXVECTOR3 vEyePt( 0.0f, 3.0f,-5.0f );
D3DXVECTOR3 vLookatPt( 0.0f, 0.0f, 0.0f );
D3DXVECTOR3 vUpVec( 0.0f, 1.0f, 0.0f );
D3DXMATRIXA16 matView;
D3DXMatrixLookAtLH( &matView, &vEyePt, &vLookatPt, &vUpVec );
g_pd3dDevice->SetTransform( D3DTS_VIEW, &matView );
// 設置視錐體大小
D3DXMATRIXA16 matProj;
D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI/4, 1.0f, 1.0f, 100.0f );
g_pd3dDevice->SetTransform( D3DTS_PROJECTION, &matProj );
}
//-----------------------------------------------------------------------------
// Name: SetupLights()
// Desc: Sets up the Lights and materials for the scene.
//-----------------------------------------------------------------------------
VOID SetupLights()
{
// 初始化一個材料
D3DMATERIAL9 mtrl;
ZeroMemory( &mtrl, sizeof(D3DMATERIAL9) );
mtrl.Diffuse = mtrl.Ambient = D3DXCOLOR(1.0f,1.0f,0.0f,1.0f); //材質有漫射和環境光的設置，都為黃色
g_pd3dDevice->SetMaterial( &mtrl );
// 初始化一個白色的方向光
D3DXVECTOR3 vecDir;
D3DLIGHT9 light;
ZeroMemory( &light, sizeof(D3DLIGHT9) );
light.Type = D3DLIGHT_DIRECTIONAL;//方向光
light.Diffuse = D3DXCOLOR(1.0f,1.0f,1.0f,1.0f);//設置光源的漫射光顏色為白色
light.Direction = D3DXVECTOR3(0.0f,0.0f,1.0f);//光的傳播方向平行z軸
light.Range = 1000.0f;
g_pd3dDevice->SetLight( 0, &light );
g_pd3dDevice->LightEnable( 0, TRUE );
g_pd3dDevice->SetRenderState( D3DRS_LIGHTING, TRUE );
// Finally, turn on some ambient light.
g_pd3dDevice->SetRenderState( D3DRS_AMBIENT, 0x00202020 );
}
//-----------------------------------------------------------------------------
// Name: Render()
// Desc: Draws the scene
//-----------------------------------------------------------------------------
VOID Render()
{
// 背景為藍色
g_pd3dDevice->Clear( 0, NULL, D3DCLEAR_TARGET|D3DCLEAR_ZBUFFER,
D3DCOLOR_XRGB(0,0,255), 1.0f, 0 );
// Begin the scene
if( SUCCEEDED( g_pd3dDevice->BeginScene() ) )
{
// 茶壺的材料顏色也定義在這個函數中
SetupLights();
// Setup the world, view, and projection matrices
SetupMatrices();
// Render the vertex buffer contents
g_pd3dDevice->SetStreamSource( 0, g_pVB, 0, sizeof(CUSTOMVERTEX) );
g_pd3dDevice->SetFVF( D3DFVF_CUSTOMVERTEX );
//創建一個茶壺
Objects = 0;
D3DXMATRIX Worlds;
D3DXCreateTeapot(g_pd3dDevice, &Objects, 0);
Objects->DrawSubset(0);
Objects->Release();
Objects=0;
// End the scene
g_pd3dDevice->EndScene();
}
// Present the backbuffer contents to the display
g_pd3dDevice->Present( NULL, NULL, NULL, NULL );
}
//-----------------------------------------------------------------------------
// Name: MsgProc()
// Desc: The window's message handler
//-----------------------------------------------------------------------------
LRESULT WINAPI MsgProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
switch( msg )
{
case WM_DESTROY:
Cleanup();
PostQuitMessage( 0 );
return 0;
}
return DefWindowProc( hWnd, msg, wParam, lParam );
}
//-----------------------------------------------------------------------------
// Name: WinMain()
// Desc: The application's entry point
//-----------------------------------------------------------------------------
INT WINAPI WinMain( HINSTANCE hInst, HINSTANCE, LPSTR, INT )
{
// Register the window class
WNDCLASSEX wc = { sizeof(WNDCLASSEX), CS_CLASSDC, MsgProc, 0L, 0L,
GetModuleHandle(NULL), NULL, NULL, NULL, NULL,
"D3D Tutorial", NULL };
RegisterClassEx( &wc );
// Create the application's window
HWND hWnd = CreateWindow( "D3D Tutorial", "D3D Tutorial 04: Lights",
WS_OVERLAPPEDWINDOW, 100, 100, 300, 300,
GetDesktopWindow(), NULL, wc.hInstance, NULL );
// Initialize Direct3D
if( SUCCEEDED( InitD3D( hWnd ) ) )
{
// Show the window
ShowWindow( hWnd, SW_SHOWDEFAULT );
UpdateWindow( hWnd );
// Enter the message loop
MSG msg;
ZeroMemory( &msg, sizeof(msg) );
while( msg.message!=WM_QUIT )
{
if( PeekMessage( &msg, NULL, 0U, 0U, PM_REMOVE ) )
{
TranslateMessage( &msg );
DispatchMessage( &msg );
}
else
Render();
}
}
UnregisterClass( "D3D Tutorial", wc.hInstance );
return 0;
}
