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authordan miller2007-10-19 05:15:33 +0000
committerdan miller2007-10-19 05:15:33 +0000
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1
2> Hi John,
3>
4> I know I'll forget to tell you this if I don't write it right now....
5>
6> >(2) How is the receiving geometry for the shadow decided?
7>
8> I wrote about an LSS-test but actually performing a new VFC test (from the
9> light's view) is the same. In both cases, here's a trick to take advantage
10> of temporal coherence : test the world against a slightly larger than
11> necessary LSS or frustum. Keep the list of touched surfaces. Then next
12> frame, if the new volume is still contained within the previous one used
13for
14> the query, you can reuse the same list immediately. Actually it's a bit
15> similar to what you did in your sphere-tree, I think. Anyway, now the
16O(log
17> N) VFC is O(1) for some frames. It's not worth it for the "real" VFC, but
18> when you have N virtual frustum to test to drop N shadows, that's another
19> story.
20>
21> Two downsides:
22> - You need more ram to keep track of one list of meshes / shadow, but
23> usually it's not a lot.
24> - By using a larger volume for the query you possibly touch more
25> faces/surfaces, which will be rendered in the shadow pass. Usually it's
26not
27> a problem either since rendering is simply faster than geometric queries
28> those days. But of course, "your mileage may vary".
29>
30> Happy new year !
31>
32> Pierre