1、D3D Alpha混合2009-04-17 13:39Direct3D計(jì)算Alpha混合的顏色公式：Color = ( SrcRGB * SrcK ) + ( DestRGB * DestK )SrcRGB表示源顏色值，即將要繪制的顏色值。SrcK表示源混合系數(shù)，通常賦值為D3DBLEND_SRCALPHA，即當(dāng)前繪制像素的Alpha值DestRGB表示目標(biāo)顏色值，即當(dāng)前緩沖區(qū)中的顏色值。DestK表示目標(biāo)系數(shù)，通常賦值為D3DBLEND_INVSRCALPHA，即1減去當(dāng)前繪制像素的Alpha值則Direct3D計(jì)算Alpha混合的顏色公式可表示為Color = ( SrcRGB * Src

2、Alpha ) + ( DestRGB * ( 1 - SrcAlpha ) )混合步驟Alpha混合默認(rèn)關(guān)閉，所以首先需要開啟它Device - SetRenderState( D3DRS_ALPHABLENDENABLE, true );然后設(shè)置Alpha混合系數(shù)Device - SetRenderState( D3DRS_SRCBLEND, D3DBLEND_SRCALPHA );Device - SetRenderState( D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);還要指定資源(材質(zhì)或Alpha通道)Alpha通道可用DirectX自帶的紋理工具

3、創(chuàng)建，為DDS文件設(shè)置可變頂點(diǎn)格式時(shí)增加一個(gè)D3DCOLOR類型的漫反射分量，其中的alpha值指定了alpha混合因子。/ The 2D vertex format and descriptortypedefstruct float x, y, z; / 2D coordinates float rhw; / rhw D3DCOLOR diffuse; / diffuse color component VERTEX;#define VERTEX_FVF (D3DFVF_XYZRHW | D3DFVF_DIFFUSE)/ initialize vertex data VERTEX verts

4、= 100.0f,100.0f,1.0f,1.0f, D3DCOLOR_RGBA(0,64,128,255) , 300.0f,100.0f,1.0f,1.0f, D3DCOLOR_RGBA(0,64,128,255) , 100.0f,300.0f,1.0f,1.0f, D3DCOLOR_RGBA(0,64,128,255) , 300.0f,300.0f,1.0f,1.0f, D3DCOLOR_RGBA(0,64,128,255) , 50.0f,150.0f,1.0f,1.0f, D3DCOLOR_RGBA(128,0,0,128) , 350.0f,150.0f,1.0f,1.0f,

5、D3DCOLOR_RGBA(128,0,0,128) , 50.0f,350.0f,1.0f,1.0f, D3DCOLOR_RGBA(128,0,0,128) , 350.0f,350.0f,1.0f,1.0f, D3DCOLOR_RGBA(128,0,0,128) ;D3DCOLOR類型可以用D3DCOLOR_RGBA宏來生成，定義如下：/ maps unsigned 8 bits/channel to D3DCOLOR#define D3DCOLOR_ARGB(a,r,g,b) (D3DCOLOR)(a)&0xff)24)|(r)&0xff)16)|(g)&0xff)SetRenderSt

6、ate(D3DRS_ALPHABLENDENABLE, FALSE); g_d3d_device-DrawPrimitive(D3DPT_TRIANGLESTRIP,0,2); / enable alpha blending and draw 2 polygons g_d3d_device-SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE); g_d3d_device-SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA); g_d3d_device-SetRenderState(D3DRS_DESTBLEND,

7、 D3DBLEND_INVSRCALPHA); g_d3d_device-DrawPrimitive(D3DPT_TRIANGLESTRIP,4,2); 完整源碼如下：/*PURPOSE: Alpha blending DemoRequired libraries: D3D9.LIB*/#include#include#included3d9.h#pragma comment(lib,d3d9.lib)#define WINDOW_WIDTH 400#define WINDOW_HEIGHT 400#define Safe_Release(p) if(p) (p)-Release();/ wi

8、ndow handles, class and caption text.HWND g_hwnd;HINSTANCE g_inst;static char g_class_name= AlphaClass;static char g_caption = Alpha Blending Demo;/ the Direct3D and device objectIDirect3D9* g_d3d= NULL;IDirect3DDevice9* g_d3d_device= NULL;/ The 2D vertex format and descriptortypedefstruct float x,

9、y, z; / 2D coordinates float rhw; / rhw D3DCOLOR diffuse; / diffuse color component VERTEX;#define VERTEX_FVF (D3DFVF_XYZRHW | D3DFVF_DIFFUSE)IDirect3DVertexBuffer9* g_vertex_buffer= NULL;IDirect3DTexture9* g_texture= NULL;/-/ Initialize d3d, d3d device, vertex buffer, texutre./-BOOL Do_Init()初始化d3d

10、設(shè)備 頂點(diǎn)緩沖區(qū) return TRUE;/-/ Release all d3d resource./-BOOL Do_Shutdown() Safe_Release(g_vertex_buffer); Safe_Release(g_d3d_device); Safe_Release(g_d3d); return TRUE;/-/ Render a frame./-BOOL Do_Frame() / clear device back buffer g_d3d_device-Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_RGBA(0,0,0,255),1.0

11、f,0); / Begin scene if(SUCCEEDED(g_d3d_device-BeginScene() / set the vertex stream, shader, and texture. / binds a vertex buffer to a device data stream g_d3d_device-SetStreamSource(0, g_vertex_buffer,0,sizeof(VERTEX); / set the current vertex stream declation g_d3d_device-SetFVF(VERTEX_FVF); / assi

12、gns a texture to a stage for a device g_d3d_device-SetTexture(0, g_texture); / disable alpha blending and draw 2 polygons g_d3d_device-SetRenderState(D3DRS_ALPHABLENDENABLE, FALSE); g_d3d_device-DrawPrimitive(D3DPT_TRIANGLESTRIP,0,2); / enable alpha blending and draw 2 polygons g_d3d_device-SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE); g_d3d_device-SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA); g_d3d_device-SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA); g_d3d_device); / end the scene g_d3d_device-EndScene(); / present the contents of the next buffer in the s