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Pentagram
08-28-2003, 08:32 AM
Hello,

Does anyone have any ideas on the techniques used for the softshadowing in the Last Chance Gas demo
(http://www.nvidia.com/object/demo_lastchancegas.html)
There are some strange textures in the textures\softshadows subdirectory... horizon maps or something??

Charles

dorbie
08-28-2003, 11:17 AM
I'd bet it's prebaked in those shots. Basically a light map.

MZ
08-28-2003, 11:47 AM
http://www.cgshaders.org/forums/viewtopic.php?t=1716&highlight=gas+station

Nutty
08-28-2003, 11:48 AM
I thought the demo did a time advance of day to night? Surely pre-baked shadows wouldn't work for this.

Could be wrong tho. Best bet is to ask Simon Green.

dorbie
08-28-2003, 01:44 PM
Originally posted by Simon Green (on cgshaders.org):
I didn't work on the Gas Station demo but I can describe the basics. The light maps were done in Softimage XSI using Mental Ray. We experimented with ambient occlusion and bent normals, but in the end
used GI/final gathering. The soft shadows were done using a hybrid technique that precomputes the times at which each point enters and leaves shadow as the sun (modelled as a linear light source) moves across the sky in a line. This information is stored in multiple textures, and a custom fragment program interpolates between these values to determine the amount of shadowing given the current time. I believe Joe Demers will be describing this in more detail in our upcoming "GPU Gems" book.

Ysaneya
08-28-2003, 02:12 PM
Now that's what i call a Trick, with a big T.

Y.

SirKnight
08-28-2003, 02:41 PM
This demo to me is just plain frickin cool. I was very impressed by it. When I watched the video of it I found it hard to keep my mouth closed. http://www.opengl.org/discussion_boards/ubb/biggrin.gif It may not be doing all of the fancy GI calcs and all that on the card in real-time (not possible yet) but it sure as heck looked like it.


-SirKnight