In article <3e205225$1@news.povray.org>,
 "Mark Hanson" <mar### [at] attbicom> wrote:

> I've been away from playing with Pov-Ray for a few years, so I haven't heard
> about this utility. Some of the pictures I've seen in p.b.i. are stunning --
> they look like photographs. I'm certainly not looking for advice on how to
> use it (I'm back up to the point where I can make a scene with spheres and
> boxes without screwing up :-) ), just a sort of basic explanation of what it
> is, and how it works. Thanks.

Basically, to make a really realistic scene, it helps for your objects 
to have realistic surroundings and lighting, especially for things like 
reflections. You can construct this environment entirely in the 
computer, having the computer actually simulate the entire scene, but 
this takes memory, computation time, and is difficult or just time 
consuming.

HDRI means High Dynamic Range Image. Usually, image color values are 
percentages, you can have 0%, 100%, and steps in between. Of course, in 
reality, there is no "100% brightness", it is just a compromise for what 
our display devices can show. High dynamic range images store 
intensities instead of percentages, and can store values brighter than 
"white".

An HDRI image can be used to store lighting values for a scene, either 
precomputed ahead of time or taken from a real-world sample. Since the 
lighting values already exist, it doesn't take as long as having the 
actual scenery there, it is easier to set up, and the lighting is more 
realistic than a background from an ordinary image, with color values 
clipped to a small range.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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