How do I render from one render target to another?

Posted by Chaotikmind on Game Development See other posts from Game Development or by Chaotikmind
Published on 2014-08-17T07:57:57Z Indexed on 2014/08/19 22:35 UTC
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Filed under:

c++

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directx9

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rendertargets

I have two render targets:

a fake backbuffer; a special render target where I do all my rendering.
a light render target; where I render my light fx.

I'm sure I'm rendering correctly on both.

The problem arises when I overlay the light render target onto the fake backbuffer by drawing a quad covering it:

DxEngine.DrawSprite(0.0f, 0.0f, 0.0f,
    (float)DxEngine.GetWidth(), (float)DxEngine.GetHeight(),
    0xFFFFFFFF, LightSurface->GetTexture());

Regardless of what's in the light target, nothing is rendered onto the other target. I tried clearing the light target with full-white or full-black, but still get nothing.

Fake backbuffer created with

Direct3dDev->CreateTexture(Width, Height, 1, D3DUSAGE_RENDERTARGET,
    D3DFMT_X8R8G8B8, D3DPOOL_DEFAULT, &Texture, nullptr);

Light render target created with

Direct3dDev->CreateTexture(Width, Height, 1, D3DUSAGE_RENDERTARGET,
    D3DFMT_A8R8G8B8, D3DPOOL_DEFAULT, &Texture, nullptr);

I also tried to create both with D3DFMT_A8R8G8B8, again without difference. Both targets have the same width and height.

Only the fixed pipeline is used

DirectX setup for rendering :

Direct3dDev->SetSamplerState(0, D3DSAMP_MINFILTER, D3DTEXF_LINEAR );
Direct3dDev->SetSamplerState(0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR );
Direct3dDev->SetSamplerState(0, D3DSAMP_MIPFILTER, D3DTEXF_NONE );
Direct3dDev->SetSamplerState(0, D3DSAMP_ADDRESSU, D3DTADDRESS_WRAP );
Direct3dDev->SetSamplerState(0, D3DSAMP_ADDRESSV, D3DTADDRESS_WRAP );
Direct3dDev->SetRenderState(D3DRS_CULLMODE, D3DCULL_NONE);
Direct3dDev->SetRenderState(D3DRS_LIGHTING, false);
Direct3dDev->SetRenderState(D3DRS_ZENABLE, D3DZB_TRUE);
Direct3dDev->SetRenderState(D3DRS_ZWRITEENABLE,D3DZB_TRUE);
Direct3dDev->SetRenderState(D3DRS_ZFUNC,D3DCMP_LESSEQUAL);

Direct3dDev->SetRenderState(D3DRS_ALPHABLENDENABLE,  true );
Direct3dDev->SetRenderState(D3DRS_ALPHAREF, 0x00000000ul);
Direct3dDev->SetRenderState(D3DRS_ALPHATESTENABLE, true);
Direct3dDev->SetRenderState(D3DRS_ALPHAFUNC,D3DCMP_GREATER);
Direct3dDev->SetRenderState(D3DRS_SRCBLEND,  D3DBLEND_SRCALPHA );
Direct3dDev->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA );

Direct3dDev->SetTextureStageState(0, D3DTSS_COLORARG1, D3DTA_TEXTURE);
Direct3dDev->SetTextureStageState(0, D3DTSS_COLORARG2, D3DTA_DIFFUSE);
Direct3dDev->SetTextureStageState(0, D3DTSS_COLOROP, D3DTOP_MODULATE);
Direct3dDev->SetTextureStageState(0, D3DTSS_ALPHAARG1, D3DTA_TEXTURE);
Direct3dDev->SetTextureStageState(0, D3DTSS_ALPHAARG2, D3DTA_DIFFUSE);
Direct3dDev->SetTextureStageState(0, D3DTSS_ALPHAOP, D3DTOP_MODULATE);

Direct3dDev->SetTextureStageState(0, D3DTSS_RESULTARG, D3DTA_CURRENT);

Direct3dDev->SetTextureStageState(0, D3DTSS_TEXCOORDINDEX, D3DTSS_TCI_PASSTHRU);

//ensure the first stage is not used for now
Direct3dDev->SetTextureStageState(1, D3DTSS_COLOROP, D3DTOP_DISABLE);

How can I do this right?

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