HDRI - Page 2 - Simply Maya User Community

# 16 19-02-2003 , 12:34 PM

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Join Date: Aug 2002

Posts: 1,135

I wouldn't associate it with global illumination per se user added image

, 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.

I do not support Bush! Nor Saddam! Long live UN!

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# 17 19-02-2003 , 02:44 PM

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Join Date: Jan 2003

Location: Denmark

Posts: 338

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... -->
https://www.rendermania.com/HDRI/index.shtml

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

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

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

"Faking HDRI in Maya"... -->
https://www.3dluvr.com/pixho/tutorial...HDRI_index.htm
"HDRI The Cheap And Nasty Way "... -->
https://www.andrew-whitehurst.net/hdri_tut.html
"Image Based Illumination - High Dynamic Range Imagery"... -->
https://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

Strarup

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# 18 01-03-2003 , 04:27 AM

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Join Date: Nov 2002

Location: Australia

Posts: 28

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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