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seb69

Screen is darkened after post processing

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Hi everyone I am new here smile.png (in DirectX at the same time).

So, I have done some post processing but I get something strange at the output, the screen is darkened.

My HLSL code is basic :

texture g_txSrcColor;
sampler2D g_samSrcColor = sampler_state
{
Texture = <g_txSrcColor>;
AddressU = Clamp;
AddressV = Clamp;
MinFilter = Linear;
MagFilter = Linear;
MipFilter = Linear;
};
float4 PostProcessPS( float2 Tex : TEXCOORD0 ) : COLOR0
{
return tex2D(g_samSrcColor, Tex);
}
technique PostProcess
{
pass p0
{
VertexShader = null;
PixelShader = compile ps_3_0 PostProcessPS();
}
}


And the other side :


#define CUSTOMFVF (D3DFVF_XYZRHW | D3DFVF_TEX1)

struct PPVERT
{
float x, y, z, rhw;
float tu, tv;
const static D3DVERTEXELEMENT9 Decl[4];
};

const D3DVERTEXELEMENT9 PPVERT::Decl[4] =
{
{ 0, 0, D3DDECLTYPE_FLOAT4, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_POSITIONT, 0 },
{ 0, 16, D3DDECLTYPE_FLOAT2, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 0 },
{ 0, 24, D3DDECLTYPE_FLOAT2, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 1 },
D3DDECL_END()
};



D3DXSaveTextureToFile("texture_in.bmp", D3DXIFF_BMP, g_pSceneTexture, NULL);
UINT nbPasses = 0;
pEffect->Begin(&nbPasses, 0);
for(UINT i = 0 ; i<nbPasses ; i++)
{
pEffect->BeginPass(i);
d3device->SetStreamSource( 0, g_pVertexQuadBuffer, 0, sizeof(PPVERT) );
d3device->SetFVF( CUSTOMFVF );
d3device->DrawPrimitive( D3DPT_TRIANGLESTRIP, 0, 2 );
pEffect->EndPass();
}
pEffect->End();
D3DXSaveSurfaceToFile("surface_out.bmp", D3DXIFF_BMP, g_pRenderSurface, NULL, NULL);


I have saved the input texture and the output surface (please have a look on the screenshots). Have I missed something? The thing is that I have no information of the scene (how the device has been initialised at the beginning, and there is three render passes) so I can not find where is the problem sad.png . If you have any ideas go ahead.

Thanks in advance,

Sébastien

texture_in : http://hpics.li/1dbe6d0

surface_out : http://hpics.li/2d85644

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this can happen if you haven't generated mip maps and sample between them (as they might be black). You can force sampling the first mip map stage by using the tex2DLod method.

This is just a guess as i think you are doing a fullscreen pass with the same resolution as the source texture (where it should sample the first mip map stage automatically) but its worth a try.

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So, I have tried tex2Dlod, unfortunately it's still the same output. Otherwise I use a screen aligned quad so it is the same resolution.

Edit: before discarding the solution, when do I have to use the tex2Dlod? I have tried this (both in VS and PS methods) :


float4 color = tex2Dlog(g_samSrcColor, float4(Tex,0.0f,0.0f));

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Just set MipFilter to None if you don't want to use mip maps.

tex2Dlod is usually used if you want to explicitely select a mip level from the sampled texture.

If the input texture has the same dimensions as the output texture, mip levels aren't used anyway.

PS: Maybe it's caused by some blending options? try setting alphablendenable to false.

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Hi froop,

I have tried :


technique PostProcess
{
pass p0
{
AlphaBlendEnable = false;
VertexShader = null;
PixelShader = compile ps_3_0 PostProcessPS();
}
}


with :


d3device->SetRenderState(D3DRS_ALPHABLENDENABLE, FALSE);


But it's still the same result sad.png. But it looks like an alpha issue... I also tried this :


float4 color = tex2D(g_samSrcColor, Tex);
return float4(color.rgb, 1.0f);


But nothing...

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Try to return a specific color, without reading the texture:

return float4(1.0f, 0, 0, 1.0f);

If you get a clean and 100 % bright red color, you'll know that the problem is somewhere in the texture lookup.
If you get a dark red color, you'll know that the problem is somewhere in the part where you render the quad.

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Try to return a specific color, without reading the texture:

return float4(1.0f, 0, 0, 1.0f);

If you get a clean and 100 % bright red color, you'll know that the problem is somewhere in the texture lookup.
If you get a dark red color, you'll know that the problem is somewhere in the part where you render the quad.


I get a clean red color..

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Maybe the sRGB flag is set it wrong.
I don’t know how to set it in DX9. You have to find out by yourself. Sorry.


It works ! Thanks, It was a gamma issue. I have to disable the gamma correction (http://msdn.microsof...v=vs.85%29.aspx).

So, it can be done both in HLSL or Direct3D.

HLSL :


sampler2D g_samSrcColor =
sampler_state
{
Texture = <g_txSrcColor>;
AddressU = Clamp;
AddressV = Clamp;
MinFilter = Linear;
MagFilter = Linear;
MipFilter = Linear;
SRGBTexture = false;
};

technique PostProcess
{
pass p0
{
VertexShader = null;
PixelShader = compile ps_3_0 PostProcessPS();
SRGBWriteEnable = false;
}
}


or Direct3D :


d3device->SetSamplerState(0, D3DSAMP_SRGBTEXTURE, 0);



Sébastien

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