# DX11 Adapting Luminance Map - No adaptation according to my eye

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Migi0027    4628

Hi guys.

so I'm currently having a minor issue here. I generate my luminance map, then attempt to adapt it and then use it for other purposes, such as the bloom pass. But the problem is that theres no visible adaptation for some reason. Someone might find the shader code familiar, well thats because I based it on a sample from MJP (Thanks btw. Great samples you have there.)

Logic in the high level render when rendering & adapting the luminance map, DX11 is my own small wrapper, it should work as intended:

void CE_NAMESPACE::CEPostLuminance::Render(DX11 *pD3D11, float dTime, DX11Resource *p, DX11RenderTarget *pOut)
{
// Set DTIME
Buffer.fTimeDelta = dTime;

// Map Data
pD3D11->BufferConstantMap(m_vBuffers[0]->p, &Buffer);

SetData(pD3D11);

// Calculate new luminance
{
pD3D11->RTVSet(&m_pLum->pRTV, 1, false);

ApplyPost(pD3D11, &m_pPasses[0]);

pD3D11->Bind(p, 0);

pD3D11->Render(3, 0);

// Unbind
pD3D11->Unbind(PS, 0);
}

{
pD3D11->RTVSet(&m_pTemp->pRTV, 1, false);

ApplyPost(pD3D11, &m_pPasses[1]);

pD3D11->Bind(m_pLumLast, 1);

pD3D11->Bind(m_pLum, 2);

pD3D11->Render(3, 0);
}

// Swappy Times!
m_pLumLast = m_pLum;
m_pLum = m_pTemp;
m_pTemp = m_pLumLast;

.... Some more unrelated stuff


...
Texture2D<float> lum_old : register(t1);
Texture2D<float> lum : register(t2);

...

{
float lastLum = exp(lum_old.Sample(ss, input.Tex));
float currentLum = lum.Sample(ss, input.Tex);

// Adapt the luminance using Pattanaik's technique
float adaptedLum = lastLum + (currentLum - lastLum) * (1 - exp(-TimeDelta * Tau));

}


The mistake is most likely obvious but theres no change in the luminance map according to my eyes.

Thank you for your time. I appreciate it.

-MIGI0027

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Juliean    7068

float adaptedLum = lastLum + (currentLum - lastLum) * (1 - exp(-TimeDelta * Tau));

Probably this line. Just quessing, but thats what caused problems at my end more than once. try to replace the exp()-statement with a constant, like

float adaptedLum = lastLum + (currentLum - lastLum) * 0.75f;

and see if it works.

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Migi0027    4628

Tried replacing the exp with 0.75f, still, no change, its most likely a simple mistake, which are the worst.

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Juliean    7068

Visualize the content of your render-targets then. How does the current/last/blended luminance looks like?Try to see if there is any change here at all first, maybe the luminance isn't even calculated properly to begin with.

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joeblack    303

Hi, can you show how are you computing luminance ?

and also your bloom pass ?

Log and exp should be used during generation of luminance, so instead of :

float lastLum = exp(lum_old.Sample(ss, input.Tex));
float currentLum = lum.Sample(ss, input.Tex);

// Adapt the luminance using Pattanaik's technique
float adaptedLum = lastLum + (currentLum - lastLum) * (1 - exp(-TimeDelta * Tau));

return log(adaptedLum);

you should have :

float lastLum = lum_old.Sample(ss, input.Tex);
float currentLum = exp(lum.Sample(ss, input.Tex));

// Adapt the luminance using Pattanaik's technique
float adaptedLum = lastLum + (currentLum - lastLum) * (1 - exp(-TimeDelta * Tau));



and use Log during generation of luminance.

Or first you can try you luminance without any log/exp and see if it works.

Edited by joeblack

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Migi0027    4628

Thanks for all the valuable help, the problem lied deeper due to a flaw in my logic and naive assumptions.

The problem was the swapping part. Im not sure when or how or why I did it like that.

WRONG: (I must have been under some sort of hallucinating drug  )

// Adapt it, no effect
{
pD3D11->RTVSet(&m_pTemp->pRTV, 1, false);

ApplyPost(pD3D11, &m_pPasses[1]);

pD3D11->Bind(m_pLumLast, 1);

pD3D11->Bind(m_pLum, 2);

pD3D11->Render(3, 0);
}

// Swappy Times! Like wtf is this!?
m_pLumLast = m_pLum;
m_pLum = m_pTemp;
m_pTemp = m_pLumLast;


The solution was two have an array called m_pLumLast of 2 elements, then casually swap them after usage:

	// Blend it
{
pD3D11->RTVSet(&m_ppLumLast[1]->pRTV, 1, false);

ApplyPost(pD3D11, &m_pPasses[1]);

pD3D11->Bind(m_ppLumLast[0], 1);

pD3D11->Bind(m_pLum, 2);

pD3D11->Render(3, 0);

// Unbind
pD3D11->Unbind(PS, 0);
}

// Swap Old Luminance Maps
DX11RenderTarget *pRCPY = m_ppLumLast[0];
m_ppLumLast[0] = m_ppLumLast[1];
m_ppLumLast[1] = pRCPY;


Ohh, and for anyone wondering, its a good idea to clear the last luminance textures after youve created them to a value, might be 0.

And thanks joeblack + juliean. But the problem was on my side, I apologize for the trouble. But thanks for the awesome help.

Perhaps someone will find this valuable at some point.

EDIT: Sorry for the long delay, but its hard finding time to test...

-MIGI0027

Edited by Migi0027

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