深度测试与alpha混合（4）
材质alpha
顶点alpha是没有使用光照和材质的情况，如果对场景内的物体添加光照和材质而没有添加纹理时，顶点alpha值取决于材质属性中漫反射颜色的alpha系数和灯光颜色中的alpha系数，顶点alpha值是根据光照计算得到的。顶点光照计算是分别针对红、绿、蓝和alpha进行的，其中alpha光照计算的结果就是顶点的alpha值。有了顶点的alpha值就可根据着色模式计算出每个像素的alpha值，第一个示例程序就是材质alpha的例子。
纹理alpha
当对物体表面使用了纹理之后，像素的alpha值就是纹理alpha混合之后的值，所以这又取决于纹理的alpha混合方法，纹理alpha混合方法决定了纹理alpha混合之后的alpha值是取自材质，还是取自纹理，或者取自二者的某种运算。像素alpha值的具体计算过程是这样的，首先得到顶点alpha值，顶点alpha值可能是直接指定的，也可能是光照计算得到，然后根据着色模式对顶点alpha值进行插值，得到的结果再根据纹理alpha混合方法和纹理采样得到的alpha值进行指定的运算，得到最终每个像素的alpha值。
示例程序中将一幅纹理应用到一个矩形表面，其中纹理alpha混合的设置如下：
g_device->SetTextureStageState(0, D3DTSS_ALPHAOP, D3DTOP_MODULATE);
g_device->SetTextureStageState(0, D3DTSS_ALPHAARG1, D3DTA_TEXTURE);
g_device->SetTextureStageState(0, D3DTSS_ALPHAARG2, D3DTA_DIFFUSE);
- D3DTOP_MODULATE
- Multiply the components of the arguments.
SRGBA = Arg1 x Arg2
在示例程序中将矩形4个顶点的颜色值设置为0xFFFFFFFF，其alpha成分设置为ff，即alpha值为1.0f，所以纹理alpha混合的最终结果就是取纹理的alpha值。
sCustomVertex vertices[] =
{
{ -3, -3, 0.0f, 0xffffffff, 0.0f, 1.0f},
{ -3, 3, 0.0f, 0xffffffff, 0.0f, 0.0f},
{ 3, -3, 0.0f, 0xffffffff, 1.0f, 1.0f},
{ 3, 3, 0.0f, 0xffffffff, 1.0f, 0.0f}
}
示例程序在一个矩形表面贴了一颗树的纹理，在树的纹理中，没有树叶和树枝的地方alpha值为0，即完全透明；有树叶和树枝的地方alpha值为1，即完全不透明。所以通过alpha混合后，渲染的结果就像是一棵真的树。
按下数字键"1"，启用纹理alpha混合。
按下数字键"0"，禁用纹理alpha混合。
将顶点alpha由ff改为88后启用纹理混合的效果，可以看出纹理的颜色变暗了。
sCustomVertex vertices[] =
{
{ -3, -3, 0.0f, 0x88ffffff, 0.0f, 1.0f},
{ -3, 3, 0.0f, 0x88ffffff, 0.0f, 0.0f},
{ 3, -3, 0.0f, 0x88ffffff, 1.0f, 1.0f},
{ 3, 3, 0.0f, 0x88ffffff, 1.0f, 0.0f}
};
源程序：
#include
<
d3dx9.h
>
#pragma warning(disable : 4127 ) // disable warning: conditional expression is constant
#define CLASS_NAME "GameApp"
#define release_com(p) do { if(p) { (p)->Release(); (p) = NULL; } } while(0)
typedef unsigned char uchar;
IDirect3D9 * g_d3d;
IDirect3DDevice9 * g_device;
IDirect3DVertexBuffer9 * g_vertex_buffer;
IDirect3DTexture9 * g_texture;
struct sCustomVertex
{
float x, y, z;
DWORD color;
float u, v;
};
#define D3DFVF_CUSTOM_VERTEX (D3DFVF_XYZ | D3DFVF_DIFFUSE | D3DFVF_TEX1)
void setup_matrices()
{
// setup world matrix
D3DXMATRIX mat_world;
D3DXMatrixIdentity( & mat_world);
g_device -> SetTransform(D3DTS_WORLD, & mat_world);
// setup view matrix
D3DXVECTOR3 eye( 0.0f , 0.0f , - 10.0f );
D3DXVECTOR3 at( 0.0f , 0.0f , 0.0f );
D3DXVECTOR3 up( 0.0f , 1.0f , 0.0f );
D3DXMATRIX mat_view;
D3DXMatrixLookAtLH( & mat_view, & eye, & at, & up);
g_device -> SetTransform(D3DTS_VIEW, & mat_view);
// setup projection matrix
D3DXMATRIX mat_proj;
D3DXMatrixPerspectiveFovLH( & mat_proj, D3DX_PI / 4 , 1.0f , 1.0f , 100.0f );
g_device -> SetTransform(D3DTS_PROJECTION, & mat_proj);
}
bool init_vb()
{
if (FAILED(D3DXCreateTextureFromFile(g_device, " tree.tga " , & g_texture)))
{
MessageBox(NULL, " Can not load texture file tree.tga! " , " ERROR " , MB_OK);
return false ;
}
sCustomVertex vertices[] =
{
{ - 3 , - 3 , 0.0f , 0xffffffff , 0.0f , 1.0f },
{ - 3 , 3 , 0.0f , 0xffffffff , 0.0f , 0.0f },
{ 3 , - 3 , 0.0f , 0xffffffff , 1.0f , 1.0f },
{ 3 , 3 , 0.0f , 0xffffffff , 1.0f , 0.0f }
/*
{ -3, -3, 0.0f, 0x88ffffff, 0.0f, 1.0f},
{ -3, 3, 0.0f, 0x88ffffff, 0.0f, 0.0f},
{ 3, -3, 0.0f, 0x88ffffff, 1.0f, 1.0f},
{ 3, 3, 0.0f, 0x88ffffff, 1.0f, 0.0f}
*/
};
g_device -> CreateVertexBuffer( sizeof (vertices), 0 , D3DFVF_CUSTOM_VERTEX, D3DPOOL_DEFAULT, & g_vertex_buffer, NULL);
void * ptr;
g_vertex_buffer -> Lock( 0 , 0 , & ptr, 0 );
memcpy(ptr, vertices, sizeof (vertices));
g_vertex_buffer -> Unlock();
return true ;
}
bool init_d3d(HWND hwnd)
{
g_d3d = Direct3DCreate9(D3D_SDK_VERSION);
if (g_d3d == NULL)
return false ;
D3DPRESENT_PARAMETERS d3dpp;
ZeroMemory( & d3dpp, sizeof (d3dpp));
d3dpp.Windowed = TRUE;
d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
d3dpp.BackBufferFormat = D3DFMT_UNKNOWN;
if (FAILED(g_d3d -> CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hwnd, D3DCREATE_SOFTWARE_VERTEXPROCESSING,
& d3dpp, & g_device)))
{
return false ;
}
if ( ! init_vb())
return false ;
setup_matrices();
g_device -> SetRenderState(D3DRS_LIGHTING, FALSE);
g_device -> SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE);
g_device -> SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA);
g_device -> SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);
g_device -> SetTextureStageState( 0 , D3DTSS_COLOROP, D3DTOP_SELECTARG1);
g_device -> SetTextureStageState( 0 , D3DTSS_COLORARG1, D3DTA_TEXTURE);
g_device -> SetTextureStageState( 0 , D3DTSS_ALPHAOP, D3DTOP_MODULATE);
g_device -> SetTextureStageState( 0 , D3DTSS_ALPHAARG1, D3DTA_TEXTURE);
g_device -> SetTextureStageState( 0 , D3DTSS_ALPHAARG2, D3DTA_DIFFUSE);
return true ;
}
void cleanup()
{
release_com(g_vertex_buffer);
release_com(g_texture);
release_com(g_device);
release_com(g_d3d);
}
void render()
{
g_device -> Clear( 0 , NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB( 55 , 5 , 5 ), 1.0f , 0 );
g_device -> BeginScene();
g_device -> SetTexture( 0 , g_texture);
g_device -> SetStreamSource( 0 , g_vertex_buffer, 0 , sizeof (sCustomVertex));
g_device -> SetFVF(D3DFVF_CUSTOM_VERTEX);
g_device -> DrawPrimitive(D3DPT_TRIANGLESTRIP, 0 , 2 );
g_device -> EndScene();
g_device -> Present(NULL, NULL, NULL, NULL);
}
LRESULT WINAPI WinProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch (msg)
{
case WM_KEYDOWN:
switch (wParam)
{
case VK_ESCAPE:
DestroyWindow(hwnd);
break ;
case 48 : // press key "0", disable alpha blend.
g_device -> SetRenderState(D3DRS_ALPHABLENDENABLE, FALSE);
break ;
case 49 : // press key "1", enable alpha blend.
g_device -> SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE);
break ;
}
break ;
case WM_DESTROY:
PostQuitMessage( 0 );
return 0 ;
}
return DefWindowProc(hwnd, msg, wParam, lParam);
}
int WINAPI WinMain(HINSTANCE inst, HINSTANCE, LPSTR, INT)
{
WNDCLASSEX wc;
wc.cbSize = sizeof (WNDCLASSEX);
wc.style = CS_CLASSDC;
wc.lpfnWndProc = WinProc;
wc.cbClsExtra = 0 ;
wc.cbWndExtra = 0 ;
wc.hInstance = inst;
wc.hIcon = NULL;
wc.hCursor = NULL;
wc.hbrBackground = NULL;
wc.lpszMenuName = NULL;
wc.lpszClassName = CLASS_NAME;
wc.hIconSm = NULL;
if ( ! RegisterClassEx( & wc))
return - 1 ;
HWND hwnd = CreateWindow(CLASS_NAME, " Direct3D App " , WS_OVERLAPPEDWINDOW, 200 , 100 , 600 , 500 ,
NULL, NULL, wc.hInstance, NULL);
if (hwnd == NULL)
return - 1 ;
if (init_d3d(hwnd))
{
ShowWindow(hwnd, SW_SHOWDEFAULT);
UpdateWindow(hwnd);
MSG msg;
ZeroMemory( & msg, sizeof (msg));
while (msg.message != WM_QUIT)
{
if (PeekMessage( & msg, NULL, 0 , 0 , PM_REMOVE))
{
TranslateMessage( & msg);
DispatchMessage( & msg);
}
render();
Sleep( 10 );
}
}
cleanup();
UnregisterClass(CLASS_NAME, wc.hInstance);
return 0 ;
}
#pragma warning(disable : 4127 ) // disable warning: conditional expression is constant
#define CLASS_NAME "GameApp"
#define release_com(p) do { if(p) { (p)->Release(); (p) = NULL; } } while(0)
typedef unsigned char uchar;
IDirect3D9 * g_d3d;
IDirect3DDevice9 * g_device;
IDirect3DVertexBuffer9 * g_vertex_buffer;
IDirect3DTexture9 * g_texture;
struct sCustomVertex
{
float x, y, z;
DWORD color;
float u, v;
};
#define D3DFVF_CUSTOM_VERTEX (D3DFVF_XYZ | D3DFVF_DIFFUSE | D3DFVF_TEX1)
void setup_matrices()
{
// setup world matrix
D3DXMATRIX mat_world;
D3DXMatrixIdentity( & mat_world);
g_device -> SetTransform(D3DTS_WORLD, & mat_world);
// setup view matrix
D3DXVECTOR3 eye( 0.0f , 0.0f , - 10.0f );
D3DXVECTOR3 at( 0.0f , 0.0f , 0.0f );
D3DXVECTOR3 up( 0.0f , 1.0f , 0.0f );
D3DXMATRIX mat_view;
D3DXMatrixLookAtLH( & mat_view, & eye, & at, & up);
g_device -> SetTransform(D3DTS_VIEW, & mat_view);
// setup projection matrix
D3DXMATRIX mat_proj;
D3DXMatrixPerspectiveFovLH( & mat_proj, D3DX_PI / 4 , 1.0f , 1.0f , 100.0f );
g_device -> SetTransform(D3DTS_PROJECTION, & mat_proj);
}
bool init_vb()
{
if (FAILED(D3DXCreateTextureFromFile(g_device, " tree.tga " , & g_texture)))
{
MessageBox(NULL, " Can not load texture file tree.tga! " , " ERROR " , MB_OK);
return false ;
}
sCustomVertex vertices[] =
{
{ - 3 , - 3 , 0.0f , 0xffffffff , 0.0f , 1.0f },
{ - 3 , 3 , 0.0f , 0xffffffff , 0.0f , 0.0f },
{ 3 , - 3 , 0.0f , 0xffffffff , 1.0f , 1.0f },
{ 3 , 3 , 0.0f , 0xffffffff , 1.0f , 0.0f }
/*
{ -3, -3, 0.0f, 0x88ffffff, 0.0f, 1.0f},
{ -3, 3, 0.0f, 0x88ffffff, 0.0f, 0.0f},
{ 3, -3, 0.0f, 0x88ffffff, 1.0f, 1.0f},
{ 3, 3, 0.0f, 0x88ffffff, 1.0f, 0.0f}
*/
};
g_device -> CreateVertexBuffer( sizeof (vertices), 0 , D3DFVF_CUSTOM_VERTEX, D3DPOOL_DEFAULT, & g_vertex_buffer, NULL);
void * ptr;
g_vertex_buffer -> Lock( 0 , 0 , & ptr, 0 );
memcpy(ptr, vertices, sizeof (vertices));
g_vertex_buffer -> Unlock();
return true ;
}
bool init_d3d(HWND hwnd)
{
g_d3d = Direct3DCreate9(D3D_SDK_VERSION);
if (g_d3d == NULL)
return false ;
D3DPRESENT_PARAMETERS d3dpp;
ZeroMemory( & d3dpp, sizeof (d3dpp));
d3dpp.Windowed = TRUE;
d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
d3dpp.BackBufferFormat = D3DFMT_UNKNOWN;
if (FAILED(g_d3d -> CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hwnd, D3DCREATE_SOFTWARE_VERTEXPROCESSING,
& d3dpp, & g_device)))
{
return false ;
}
if ( ! init_vb())
return false ;
setup_matrices();
g_device -> SetRenderState(D3DRS_LIGHTING, FALSE);
g_device -> SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE);
g_device -> SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA);
g_device -> SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);
g_device -> SetTextureStageState( 0 , D3DTSS_COLOROP, D3DTOP_SELECTARG1);
g_device -> SetTextureStageState( 0 , D3DTSS_COLORARG1, D3DTA_TEXTURE);
g_device -> SetTextureStageState( 0 , D3DTSS_ALPHAOP, D3DTOP_MODULATE);
g_device -> SetTextureStageState( 0 , D3DTSS_ALPHAARG1, D3DTA_TEXTURE);
g_device -> SetTextureStageState( 0 , D3DTSS_ALPHAARG2, D3DTA_DIFFUSE);
return true ;
}
void cleanup()
{
release_com(g_vertex_buffer);
release_com(g_texture);
release_com(g_device);
release_com(g_d3d);
}
void render()
{
g_device -> Clear( 0 , NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB( 55 , 5 , 5 ), 1.0f , 0 );
g_device -> BeginScene();
g_device -> SetTexture( 0 , g_texture);
g_device -> SetStreamSource( 0 , g_vertex_buffer, 0 , sizeof (sCustomVertex));
g_device -> SetFVF(D3DFVF_CUSTOM_VERTEX);
g_device -> DrawPrimitive(D3DPT_TRIANGLESTRIP, 0 , 2 );
g_device -> EndScene();
g_device -> Present(NULL, NULL, NULL, NULL);
}
LRESULT WINAPI WinProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch (msg)
{
case WM_KEYDOWN:
switch (wParam)
{
case VK_ESCAPE:
DestroyWindow(hwnd);
break ;
case 48 : // press key "0", disable alpha blend.
g_device -> SetRenderState(D3DRS_ALPHABLENDENABLE, FALSE);
break ;
case 49 : // press key "1", enable alpha blend.
g_device -> SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE);
break ;
}
break ;
case WM_DESTROY:
PostQuitMessage( 0 );
return 0 ;
}
return DefWindowProc(hwnd, msg, wParam, lParam);
}
int WINAPI WinMain(HINSTANCE inst, HINSTANCE, LPSTR, INT)
{
WNDCLASSEX wc;
wc.cbSize = sizeof (WNDCLASSEX);
wc.style = CS_CLASSDC;
wc.lpfnWndProc = WinProc;
wc.cbClsExtra = 0 ;
wc.cbWndExtra = 0 ;
wc.hInstance = inst;
wc.hIcon = NULL;
wc.hCursor = NULL;
wc.hbrBackground = NULL;
wc.lpszMenuName = NULL;
wc.lpszClassName = CLASS_NAME;
wc.hIconSm = NULL;
if ( ! RegisterClassEx( & wc))
return - 1 ;
HWND hwnd = CreateWindow(CLASS_NAME, " Direct3D App " , WS_OVERLAPPEDWINDOW, 200 , 100 , 600 , 500 ,
NULL, NULL, wc.hInstance, NULL);
if (hwnd == NULL)
return - 1 ;
if (init_d3d(hwnd))
{
ShowWindow(hwnd, SW_SHOWDEFAULT);
UpdateWindow(hwnd);
MSG msg;
ZeroMemory( & msg, sizeof (msg));
while (msg.message != WM_QUIT)
{
if (PeekMessage( & msg, NULL, 0 , 0 , PM_REMOVE))
{
TranslateMessage( & msg);
DispatchMessage( & msg);
}
render();
Sleep( 10 );
}
}
cleanup();
UnregisterClass(CLASS_NAME, wc.hInstance);
return 0 ;
}
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