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Has AlphaBlend to do with IDirect3DSurface9?

Started by jiangcaiyang Feb 27, 2011 at 2:35 AM 1 replies 2.2k views

Original Post

Feb 27, 2011 at 2:35 AM

I am recently build up my own Game engine using DX 9,Now I've switched to render system, and I planned to have two versions, one for 2D and the other for 3D.
For 2D rendering. I wonder that whether AlphaBlend has to do with IDirect3DSurface9? I used the following code:


 // ???????
 if ( FAILED( g_pDevice->CreateOffscreenPlainSurface(
 clientWidth, // ?
 clientHeight, // ?
 D3DFMT_X8R8G8B8, // D3D??
 D3DPOOL_SYSTEMMEM, // ?????
 &g_pSurface, // ??????????
 NULL/*????*/ ) ) ) return;
 
 // ????????
 if ( FAILED( D3DXLoadSurfaceFromFile(
 g_pSurface, // ????
 NULL, // ?????
 NULL, // ????
 "?????.png", // ?????
 NULL, // ???
 D3DX_DEFAULT, // ???
 D3DCOLOR_XRGB( 0, 0, 0 ), // ????????
 NULL/*?????*/ ) ) ) return;
 
 // ??Alpha??
 g_pDevice->SetRenderState( D3DRS_ALPHABLENDENABLE, TRUE );
 g_pDevice->SetRenderState( D3DRS_SRCBLEND, D3DBLEND_SRCALPHA );
 g_pDevice->SetRenderState( D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA );

But when comes to rendering, the alphablend doesn't work. It seems that alphablend has not to do with IDirect3DSurface9.

How could I solve the problem?

jiangcaiyang

Mar 2, 2011 at 5:45 AM

Keep my thread up!

Hodgman

Mar 2, 2011 at 6:00 AM

Enabling the alpha blending render-state will cause the next draw-call to be blended with the back buffer, based on the alpha value outputted by that draw-calls pixel shader or fixed-function texture combiner settings.

What is that surface used for? Is it used as a texture in a draw-call that follows the SetRenderState calls?

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