ENenos_feedler·May 13, 2014Submission
Embree ray tracing kernels repository.
2 points · Open discussionRenderKit
embree
C++2013–2014
RenderKit / embree
embree
Embree ray tracing kernels repository.
2Distinct people
2Mentions
0Explicit recommenders
2.8KGitHub stars
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What it is
Embree ray tracing kernels repository.
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This week on Hacker News
Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 11:56:56 AM UTC.
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Mentions over time
HN mentions by month2 dated mentions
Observed mentions: 2013-10-06 07:30:40 UTC to 2014-05-13 05:40:18 UTC.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| Oct 2013 | 2013-10-01 00:00:00 UTC | 2013-11-01 00:00:00 UTC | 1 | 0 | 1 |
| Nov 2013 | 2013-11-01 00:00:00 UTC | 2013-12-01 00:00:00 UTC | 0 | 0 | 0 |
| Dec 2013 | 2013-12-01 00:00:00 UTC | 2014-01-01 00:00:00 UTC | 0 | 0 | 0 |
| Jan 2014 | 2014-01-01 00:00:00 UTC | 2014-02-01 00:00:00 UTC | 0 | 0 | 0 |
| Feb 2014 | 2014-02-01 00:00:00 UTC | 2014-03-01 00:00:00 UTC | 0 | 0 | 0 |
| Mar 2014 | 2014-03-01 00:00:00 UTC | 2014-04-01 00:00:00 UTC | 0 | 0 | 0 |
| Apr 2014 | 2014-04-01 00:00:00 UTC | 2014-05-01 00:00:00 UTC | 0 | 0 | 0 |
| May 2014 | 2014-05-01 00:00:00 UTC | 2014-06-01 00:00:00 UTC | 1 | 1 | 0 |
What Hacker News says
2 sourcesHi there, speaking of autovectorization, I actually tried it on this last night. After seeing kid0man's post, I decided to try optimizing it and selected that same loop as my target. (When I wrote the original C++ program, I was favoring conciseness and portability over performance, naturally.)
I made many of the same transformations as you did: switching the object's data to a structure of arrays, splitting out the computation of the normal from the loop, etc. (even an int hit = -1.) My goal was to coax Intel's compiler into autovectorizing that loop, without directly using vector intrinsics. I succeeded, but the result turned out to be noticeably slower than just compiling kid0man's with -fast. Part of that, I suspect is that it generated suboptimal code for the reduction over the minimum, where a human programmer would have used a
Read the rest
movemask as you did.
That said, I'm fairly curious to experiment with seeing how it would perform with the kernel compiled via ispc [1].
Regarding direct use of SIMD intrinsics in inner loops, I have to agree with you that it's still reasonably common for this type of thing. I've certainly done it before in ray tracing contexts [2], and I've seen many others do it as well, e.g. [3] and [4]. Autovectorization and things like Intel's array notation extension [5] seem to be getting better all the time, but I don't think it's generally as performant yet as direct use of intrinsics. In the cases where it is, it usually seems to have taken a fair amount of coaxing and prodding.
[1] http://ispc.github.io/
[2] http://www.cs.utah.edu/~aek/research/triangle.pdf
[3] https://github.com/embree/embree
[4] http://visual-computing.intel-research.net/publications/pape...
[5] http://software.intel.com/en-us/blogs/2010/09/03/simd-parall...