High Dynamic Range question...

I saw in the ATI demo that you can produce HDR image and animation in

real time...My question is, how can you produce

the 4 different exposition of the same image in real time ?

I can produce an image with a range of color from 0-255

How do you produce the underexposed and overexposed image ?

And then what is the blend it does to combine them ?

Any people who use HDR in Game or real time ?

Here is some static image that do HDR image...

http://www.pixeltale.com/barriles.php

http://www.pixeltale.com/psycho.php

http://www.pixeltale.com/day.php

http://www.pixeltale.com/hangar.php

[1040 byte] By [Etienne2005] at [2007-12-24]