Search found 11 matches

by outofspace
Fri Sep 06, 2013 4:32 pm
Forum: Links & Papers
Topic: HLBVH performance etc.
Replies: 7
Views: 10810

Re: HLBVH performance etc.

mpeterson: just FYI, all my code is open source since years: http://code.google.com/p/slash-sandbox/wiki/NIH. there's both 32- and 64-bit LBVH builders, as well as binned-SAH and longest-axis sweep SAH builders in there (the latter having roughly the same quality and speed of the binned SAH builder ...
by outofspace
Mon Jan 23, 2012 12:29 pm
Forum: General Development
Topic: consistency and unbiasedness
Replies: 6
Views: 5390

Re: consistency and unbiasedness

The deeper problem is that you can construct scenes which are arbitrarily close to the SDS case, and in the limit local path sampling techniques will fail. This means that you can get arbitrarily close to failing, i.e. get arbitrarily high variance. In reality, if you try to model a real camera (wit...
by outofspace
Sun Jan 22, 2012 9:37 am
Forum: General Development
Topic: consistency and unbiasedness
Replies: 6
Views: 5390

Re: consistency and unbiasedness

Sure, as I said, unbiasedness gives the tools of probability theory to analyze convergence speed. Unfortunately variance is the square of the error though, which varies with O(N^1/2) - not that good in practice. ;) And I find it interesting that to attain a desirable convergence speed people have go...
by outofspace
Sat Jan 21, 2012 11:38 am
Forum: General Development
Topic: consistency and unbiasedness
Replies: 6
Views: 5390

consistency and unbiasedness

Just wanted to repeat an argument that we ended up discussing off-topic in another thread: Many in graphics seem to think that unbiasedness offers some great advantage over consistency. Well, it's not really the case - let me explain why in very simple terms. All that unbiased means in practice is t...
by outofspace
Sat Jan 21, 2012 11:25 am
Forum: GPU
Topic: Dissapointing building times from lbvh gpu based builder
Replies: 35
Views: 27613

Re: Dissapointing building times from lbvh gpu based builder

Yes - this is a fine point, that many in graphics don't seem to get. All that unbiased means in practice is that, thanks to the Central Limit Theorem, an infinite sum of finite runs will converge to zero error. (it also means that each run has an expected error of zero over infinitely many realizati...
by outofspace
Thu Jan 19, 2012 6:02 pm
Forum: GPU
Topic: Dissapointing building times from lbvh gpu based builder
Replies: 35
Views: 27613

Re: Dissapointing building times from lbvh gpu based builder

Sure - some care is needed in everything one does. ;)
by outofspace
Thu Jan 19, 2012 5:20 pm
Forum: GPU
Topic: Dissapointing building times from lbvh gpu based builder
Replies: 35
Views: 27613

Re: Dissapointing building times from lbvh gpu based builder

Way too much importance is given to unbiasedness. Consistency is completely fine if there is a way to control the error. Remember that "statiscally accurate" doesn't buy you anything if all you get is noise. In other words, if the amount of error you get in the form of bias+variance is the same or l...
by outofspace
Wed Jan 18, 2012 10:17 am
Forum: GPU
Topic: Dissapointing building times from lbvh gpu based builder
Replies: 35
Views: 27613

Re: Dissapointing building times from lbvh gpu based builder

Have I ever mentioned global illumination or full light transport simulation ? ;) I just said ray tracing . It's now possible to solve primary and a little secondary visibility on fully dynamic models at rates that were previously possible only with rasterization, that's it. The rest is pretty much ...
by outofspace
Mon Jan 16, 2012 4:45 pm
Forum: GPU
Topic: Dissapointing building times from lbvh gpu based builder
Replies: 35
Views: 27613

Re: Dissapointing building times from lbvh gpu based builder

spectral: I was not referring to Kirill's frustum paper (which however seems pretty clear to me), but to our joint work on HLBVH (and to his separate work on "Grid SAH", which I also plan to include in nih over time). As to SBVH: while it's certainly the algorithm which produces the best trees for a...
by outofspace
Mon Jan 16, 2012 1:20 pm
Forum: GPU
Topic: Dissapointing building times from lbvh gpu based builder
Replies: 35
Views: 27613

Re: Dissapointing building times from lbvh gpu based builder

Ethernal lack of time? The paper implementation was researchy code, and needed to be cleaned up before being ready to be published (as I think you well know for your own work stuff ;) But instead of just giving out a cleaned up implementation of hlbvh alone, I decided it was far better to build a wh...