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AliasBinman

Member Since 07 Oct 2007
Offline Last Active Oct 16 2014 10:10 AM

Topics I've Started

Standard expansion of DXTn colors?

21 January 2013 - 03:06 PM

Is the way the 5.6.5. colors expanded into 8 bits or normalised floats documented/standardized anywhere. Specifically for DX9 and DX11.

So this could be done a few different ways. For Red and Blue the binary values can be divided by 31.0f to give a color in the range 0.0 to 1.0.

Alternatively the color could be expanded into 8 bits and then divided by 255. A common way of expanding bits to large word sizes is to replicate high order bits to the low order bits. So to expand 5 bits in the work ABCDE to 8 bits is ABCDEABC. Is this what occurs for DXTn?

Explanation for the Toe in Filmic Tonemapping

28 November 2012 - 11:31 AM

I've been trying to come up with why there is a toe in some tonemapping operators. Specifically a filmic type.

What I mean by this is that typically the film response starts off slowly, then becomes a close to linear response in the the middle and and then tails off at the shoulder.

I can understand the reasoning for why the shoulder happens. In the case of film the chance of a photon hitting a non exposed film element tails off as more of it is already exposed. In the case of a digital sensor then again the number of discharged CCD elements gets larger the higher the exposure.

However I cannot understand why this would happen for the toe. I would expect film to behave like a Reinhard operator which is virtually linear at the bottom

Thanks

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