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Shadow Edge Map

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To restrict the expensive filters that create the soft penumbra I want to look into shadow edge maps. I would appreciate any pointer or explanation on how to create them. Thanks in advance, - Wolf

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Thanks for the help. I already found that paper, but I am not quite sure if this is feasible and usable. They seem to use a several passes approach that involves shadow volumes ... does not sound like a real-time approach to me from first sight.
So did you follow this paper to achieve the shadow edge map?

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No, I was actually unaware of it. I just read it, and it seems stupid -- a friend who did know about it agrees. Basically it might provide minor improvements in image quality over SVs, while considerably complicating things in the process. Additionally, it doesn't support soft shadowing because it's basically SV at the edges, which is totally useless.

It's real-time, but it just takes all the weaknesses of both maps and volumes and merges them.

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Quote:
Basically it might provide minor improvements in image quality over SVs,

If you've going to quote me, Promit, at least get it right [rolleyes]. It's performance gains a minor improvement (if any). Image quality of shadow silhouette maps are identical to SVs.

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I actually got the image quality thing from the paper...although tbh I was falling asleep at that point. Oh, and apparently in certain situations it manages to suffer from shadow map artifacts anyway.

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I remember an ATI presentation on GDC 2005, where Jason Mitchell talked about shadow edge maps. He outlined a few techniques to do it, but I really couldn't see how this works outside of the simple example program.
It seems that a shadow edge map technique is used in Dungeon Siege 2, but I did not find any useful data on it.
Another way to find a shadow edge is to run 4 or 8 samples upfront, look at the result and then run the expensive filter if it is a shadow edge or a cheap lookup if it is in the umbra.
I will check this out next ...

Thanks for all your help,
- Wolf

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