Attila T. Áfra's blog about pixels, voxels and threads

Archive for the ‘AVX’ Category

Faster Incoherent Ray Traversal Using 8-Wide AVX Instructions

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Faster Incoherent Ray Traversal Using 8-Wide AVX Instructions
Attila T. Áfra
Technical Report


Efficiently tracing randomly distributed rays is a highly challenging problem on wide-SIMD processors. The MBVH (multi bounding volume hierarchy) is an acceleration structure specifically designed for incoherent ray tracing on processors with explicit SIMD architectures like the CPU. Existing MBVH traversal methods for CPUs target 4-wide SIMD architectures using the SSE instruction set. Recently, a new 8-wide SIMD instruction set called AVX has been introduced as an extension to SSE. Adapting a data-parallel algorithm to AVX can lead to significant, albeit not necessarily linear, speed improvements, but this is often not straightforward. In this paper we present an improved MBVH ray traversal algorithm optimized for AVX, which outperforms the state-of-the-art SSE-based method by up to 25%.

Paper: PDF
Citation: BibTeX

Any feedback is welcome!


Written by Attila Áfra

August 14, 2013 at 5:27 pm

Incoherent Ray Tracing without Acceleration Structures

with 6 comments

At Eurographics 2012, I presented an efficient incoherent ray tracing method that does not use any acceleration structures, and is optimized for AVX. It is based on the algorithm introduced in the HPG 2011 poster Efficient Ray Tracing without Auxiliary Acceleration Data Structure by Alexander Keller and Carsten Wächter.

Incoherent Ray Tracing without Acceleration Structures
Attila T. Áfra
Eurographics 2012 Short Paper

Recently, a new family of dynamic ray tracing algorithms, called divide-and-conquer ray tracing, has been introduced. This approach partitions the primitives on-the-fly during ray traversal, which eliminates the need for an acceleration structure. We present a new ray traversal method based on this principle, which efficiently handles incoherent rays, and takes advantage of the SSE and AVX instruction sets of the CPU. Our algorithm offers notable performance improvements over similar existing solutions, and it is competitive with powerful static ray tracers.

Paper (personal copy): PDF
Paper (definitive version): available at diglib.eg.org
Slides: PPTX (with notes, video), PDF

Written by Attila Áfra

April 24, 2012 at 1:51 am

Improving BVH Ray Tracing Speed Using the AVX Instruction Set

with 2 comments

Last week I’ve attended Eurographics 2011 in Llandudno, UK and I’ve presented my poster entitled Improving BVH Ray Tracing Speed Using the AVX Instruction Set. If you are interested, you can download a personal copy of the paper and the poster. My work, along with all the other posters presented at the conference, can also be found at the Eurographics Digital Library.

Update: now you can download an interactive demo of the methods described in the paper!

The beautiful town of Llandudno in Wales

Written by Attila Áfra

April 19, 2011 at 1:22 pm