Fastest AABB-ray test today? back

(L) [2014/01/27] [tby toshiya] [Fastest AABB-ray test today?] Wayback!

I am currently using the "optimized version" of this method:
[LINK http://people.csail.mit.edu/amy/papers/box-jgt.pdf]
but I started wondering if it sill is an efficient approach today because of the number of conditional branches. For example, I've tried to add some early-outs based on the distance along the ray found so far, but it's slower than the original version.
I am also curious how a SIMD implementation for single-AABB and single-ray performs. My experience is that, for single-AABB and single-ray, using SIMD is actually a bit slower due to horizontal ops, which apparently would be different with today's architectures.
I am thus not sure what would be "the" fastest approach today. Can someone share your wisdom and experience on it?

(L) [2014/01/28] [tby patrickwalz] [Fastest AABB-ray test today?] Wayback!

While this isn't exactly a direct answer to your question (as it is not is not directly a RAY/AABB test), I assume you are using this with a tree structure. I recently came across the paper "Ray-Box Culling for Tree Structures" which claims to accelerate tree structures pretty well with just a simple modification. Hope this at least somewhat answers your question.
[LINK http://www.iis.sinica.edu.tw/page/jise/FILE/AcceptedList/110/110367-ERB.pdf]

(L) [2014/01/29] [tby graphicsMan] [Fastest AABB-ray test today?] Wayback!

Hi Toshiya -
I found that the for loop version referenced here
[LINK http://tog.acm.org/resources/RTNews/html/rtnv19n1.html#art7]
(the one that Eric discussed with Solomon) was quite fast.  I think I made some small tweaks to that version, but it was substantially the same.  It turned out to be the fastest mono-ray mono-box test that I could find.

(L) [2014/01/29] [tby patrickwalz] [Fastest AABB-ray test today?] Wayback!

Have you by chance looked at the paper "Ray-Box Culling for Tree Structures"?
[LINK http://www.iis.sinica.edu.tw/page/jise/FILE/AcceptedList/110/110367-ERB.pdf]

(L) [2014/01/29] [tby toxie] [Fastest AABB-ray test today?] Wayback!

The idea from the paper isn't so bad in itself (shift work from the tree construction to the actual traversal, and improve upon the number of intersection tests as a bonus), but the additional storage for the BBoxes of the triangles is a bummer.
Did anybody implement this already in a "modern" ray tracer (GPU or SIMD based)?

(L) [2014/01/30] [tby patrickwalz] [Fastest AABB-ray test today?] Wayback!

apologies for the double post - wasn't aware posts had to be approved and just couldnt figure out why nothing would go through

(L) [2014/01/30] [tby jbikker] [Fastest AABB-ray test today?] Wayback!

>> patrickwalz wrote:apologies for the double post - wasn't aware posts had to be approved and just couldnt figure out why nothing would go through
Just the first one or two posts, so the security will not bother you from now on. It's inconvenient, but it got the spam down to almost zero.

(L) [2014/01/30] [tby toshiya] [Fastest AABB-ray test today?] Wayback!

Thank you for the replies!
I managed to slightly speed up mine (whopping 2%...) by following this code:
[LINK http://tog.acm.org/resources/RTNews/html/rtnv21n1.html#art9]
which uses a fewer branches as I suspected it should be. The article posted by graphicsMan (which links to the above) concluded that one should not spend time on optimizing ray-AABB tests anymore, but in some renders that I wrote, ray-AABB tests end up taking non-negligible amount of computation time, so I really wanted to see if I can speed it up. Perhaps we need a completely different algorithm to achieve further speedup.
As for the paper pointed by patrickwalz, while I agree with toxie that the idea is good, I don't know if it improves the overall performance. It seems that the point of this paper is to make a tree with many triangles per leaf not that slow -  we wouldn't use such a tree to begin with for static scenes. I am also curious if it does something with a more modern ray tracer, such as those based on HLBVH.