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Old 19-02-2003, 11:34 AM   #16
undseth
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I wouldn't associate it with global illumination per se , but it can act as a light source with final gathering.

And as a hdri file is a high dynamic range image, it is supposed to give off more accuratly light-intensities (if I remember correctly), in terms of contrast.
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Old 19-02-2003, 01:44 PM   #17
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Hi astroboii,

HDRI is not just for Maya... HDRI stands for "High Dynamic Range Images"... you can get some more information about HDRI on this site from RenderMania... -->
http://www.rendermania.com/HDRI/index.shtml

on 3d-Palace they have a Maya HDRI tutorial, in their video tutorail section... -->
http://www.3d-palace.com/modules.php...torial&sortby=

some of the things in the video tutorial are also mentioned on this site... -->
http://www.edharriss.com/tutorials/t...inxsi_eng.html
the tool "HDRI2XSI" that is used in the video, can be downloaded on this site... -->
http://www.edharriss.com/xsi/tools/tools.htm

you can also get a bit more information here...

"Faking HDRI in Maya"... -->
http://www.3dluvr.com/pixho/tutorial...HDRI_index.htm
"HDRI The Cheap And Nasty Way "... -->
http://www.andrew-whitehurst.net/hdri_tut.html
"Image Based Illumination - High Dynamic Range Imagery"... -->
http://www.accad.ohio-state.edu/~bst...6/ibi_hdr.html


how it specific works I don't know, I'm a newbie and haven't tried this things yet... but maybe some of the others can tell some more about it... :-)

regards

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Old 01-03-2003, 03:27 AM   #18
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With HDR images, each pixel isn't only represented by R G and B values ranging from 0 to 255, there's also a fourth value that stores light intensity and is a limitless float value (eg 0.48737838).

So while in a normal 'Low Dynamic Range Image' like a jpeg file, the sun may have pixels that are 255,255,255, (bright white) and a persons shoe may have a pixel that's 0,15,108, (dark blueish), the most brightness difference they can have is 255. Get it? Pure light is only 255 time brighter than pure darkness.

But with a HDR image the 'light intensity' value of a shoe pixel could be 0.0000000557 and the 'light intensity' value of the sun could be 78783934.995.

So basically, there is a very high range of intensity in a hdr image.

I hope that made sense.
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