What made HDRI make sense to me was the idea/fact that it was "invented" to
allow artificial 3D objects to be placed into a "real" scene.

Have you ever watched a program with CGI in an "real" scene where the CGI
just didn't look quite right, but you couldn't quite put your finger on why?
The likely cause was the improper lighting.  HDRI samples light differently
than, say, a single exposure on a digital camera.  From what I understand,
it does this by having multiple exposures of different lengths.  By doing
this, it can approximate the "real" intensity of the light.  By using this
light data, you can then place 3D objects into a "real" scene and have much
better lighting.

A good example is simply sunlight coming trough a window into a dark room.
On a normal photograph, the window may simply look "white".  However, having
a white piece of paper hanging on the wall does not begin to have the same
effect on lighting as sunlight coming through a window.  If you consider
all-white to be rgb<1,1,1>, then sunlight would be something like
rgb<1000,1000,1000>, but a normal digital photo can only show things in the
range rgb<0,0,0> to rgb<1,1,1>, so you'd lose all of that extra light.

I'm not sure if that made sense or not.  If you're like me, you'll be
driving down the road and suddenly go, "Hey, that makes sense now!"

Good Luck,

Slash

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