[REQ] Inverse Tone Mapping

[Caronte]

This new technique use standar LDRI images to get a kind of HDRI illumination.
It's very cool, because a huge amount of environment maps are simply jpg
http://www.banterle.com/Francesco/itmo.html
Would be nice if Indigo could use a panorama JPG (from photos) to illuminate the scene

[Kram1032]

-> also an idea to get kinda-HDR-textured Emitters
I already wondered,why such a thing doesn't exist.

[mrCarnivore]

You could also convert the ldr into hdr using hdrshop or photoshop and then simply use it in indigo....

[Kram1032]

yes, that's what I meant. but theefore, you first need to convert your jpg to ldr

[StompinTom]

yes, that's what I meant. but theefore, you first need to convert your jpg to ldr

ldr=low dynamic range
which is basically any 8 bit image (jpg, png, bmp, etc etc) because you cant have much of a dynamic range within 8 bits.

hdr=high dynamic range=way more bits per pixels(=bigger file size)

that conversion technique is cool, but as you see in one of the test images, any smooth transition is lost and instead you end up with a bunch of hard shadows. its easier to get rid of unneeded data than to try to interpolate data from nothing.

[Kram1032]

oh, ok... hum... But this converts ldr to more accurate (not entirely accurate) hdr.
it bleaches out bright spots, makes dark spots brighter and reverse.
In the three pics, you can see, that the only problem is, that the shadow is too hard, but else, it's just great.
You can't do that with simply renaming (more or less) a jpg to exr...

[StompinTom]

true, cuz AFAIK all it does is 'stretches' the 8 bits into something higher like 32, thereby creating those stepped transitions. its like taking a really dark image into photoshop and clipping its levels real low.

[Zom-B]

Hereanother interesting Paper.

[banty]

Hello everybody!
I'm the first authour of the first paper.

true, cuz AFAIK all it does is 'stretches' the 8 bits into something higher like 32, thereby creating those stepped transitions. its like taking a really dark image into photoshop and clipping its levels real low.

It's true the inverse tone mapping is a kind of strechting, however the interpolation using the exand map is meant to avoid big step transitions. Using a larger radius (25%) in the density map for creating the expand map you can attenuate hard shadows, it's not 100% perfect as in using an HDRI but it's quite near. I've just updated my website with new results if you want to check it out:
http://www.banterle.com/francesco/itmo.html

[Kram1032]

@banty:
do you think, it would be possible, to use an adaptive radius, to get even better results?

(No idea, how to, but maybe, the brighter, the wider, or something, like that...)