Oculus Rift and eye tracking

People on twitter are starting to mention that their Oculus DK2 are being shipped or are arriving. Exciting.

Meanwhile some people have mentioned how eye tracking could be a great addition to a VR set, and some have even started hacking their headset. See for example:

So what’s the point? One use is explained in this paper: Foveated Real-Time Ray Tracing for Virtual Reality Headset. In this excerpt from AMD Developer Summit 2013, the rendering architect of the Frosbite engine, Johan Andersson talks briefly about foveated rendering.

Long story short: Oculus and eye tracking could really mean real-time ray tracing in a matter of years.

Exciting. But I’m repeating myself.

The rendering tools in the film industry

Here is a list of articles published by fxguide, giving fascinating insights into the tools used by the film industry in terms of rendering.

  • Ben Snow: the evolution of ILM’s lighting tools (January 2011)
    A presentation of the evolution of the technology and tools used at Industrial Light and Magic, over the course of the years and movies, from the mid-90s to nowadays.
  • Monsters University: rendering physically based monsters (June 2013)
  • The Art of Rendering (April 2012)
    A description of the different techniques used in high end rendering and the major engines.
  • The State of Rendering (July 2013): part 1, part 2
    A lengthy overview of the state of the art in high end rendering, comparing the different tools and rendering solutions available, their approach and design choices, strengths and weaknesses as well as the consequences in terms of quality, scalability and render time.

(Brace yourselves for the massive tag list hereafter.)

A list of important graphics research papers

This is an announcement that got all my attention. Since Twitter is a mess to find anything older than a day, here is the list so far:

  1. A Characterization of Ten Hidden-Surface Algorithms, Sutherland et al., ACM Computing Surveys, 1974
  2. Survey of Texture Mapping, Paul Heckbert, IEEE Computer Graphics and Applications, 1986
  3. Rendering Complex Scenes with Memory-Coherent Ray Tracing, Matt Pharr et al., proceedings of SIGGRAPH, 1997
  4. An Efficient Representation for Irradiance Environment Maps, Ramamoorthi & Hanrahan, proceedings of SIGGRAPH, 2001
  5. Decoupled Sampling for Graphics Pipelines, Ragan-Kelley et al. ACM Transactions on Graphics, 2011
  6. The Aliasing Problem in Computer-Generated Shaded Images, Franklin C. Crow, Communications of the ACM, 1977
  7. Ray Tracing Complex Scenes, Kay & Kajiya, proceedings of SIGGRAPH, 1986
  8. Hierarchical Z-buffer Visibility, Greene et al., proceedings of SIGGRAPH, 1993
  9. Geometry Images, Gu et al., ACM Transactions on Graphics, 2002
  10. A Hidden-Surface Algorithm with Anti-Aliasing, Edwin Catmull, proceedings of SIGGRAPH, 1978
  11. Modeling the Interaction of Light Between Diffuse Surfaces, Goral et al., proceedings of SIGGRAPH, 1984
    “The first radiosity paper, with the real physical Cornell box (which I’ve actually have seen in real life!)”
  12. Pyramidal Parametrics, Lance Williams, proceedings of SIGGRAPH, 1983
  13. Rendering synthetic objects into real scenes: bridging traditional and image-based graphics with global illumination and high dynamic range photography, Paul Debevec, proceedings of SIGGRAPH 2008
    “Influence on gfx proportional to title length!”
  14. A parallel algorithm for polygon rasterization, Juan Pineda, proceedings of SIGGRAPH, 1988
  15. Rendering from compressed textures, Beers et al., proceedings of SIGGRAPH 1996
    “This one (out of 3) of the 1st texture compression papers ever! Uses VQ so probably not something you want today, but major eye opener!”
  16. A general version of Crow’s shadow volumes, P. Bergeron, IEEE Computer Graphics and Applications, 1986
    “Generalized SV. Nice trick”
  17. Reality engine graphics, Kurt Akeley, proceedings of SIGGRAPH 1993
    “Paper describes MSAA, guard bands, etc etc”
  18. The design and analysis of a cache architecture for texture mapping, Hakura and Gupta, proceedings of ISCA 1997
    “Classic texture $ paper!”
  19. Deep shadow maps, Lokovic and Veach, proceedings of SIGGRAPH 2000
    “Lots of inspiration here!”
  20. The Reyes image rendering architecture, Cook et al., proceedings of SIGGRAPH 1987
    “Sooo good & mega-influential!”
  21. A practical model for subsurface light transport, Jensen et al., proceedings of SIGGRAPH 2001
  22. Casting curved shadows on curved surfaces, Lance Williams, proceedings of SIGGRAPH 1978
    “*the* shadow map paper!”
  23. On the design of display processors, Myer and Sutherland, Communications of the ACM 1968
    “Wheel of reincarnation”
  24. Ray tracing Jell-O brand gelatin, Paul S. Heckbert, Communications of the ACM 1988
  25. Talisman: Commodity realtime 3D graphics for the PC, Torborg and Kajiya, Proceedings of SIGGRAPH 1996
  26. A Frequency Analysis of Light Transport, Durand et al., Proceedings of SIGGRAPH 2005
    “Very influential!!”
  27. An Ambient Light Illumination Mode (behind a paywall), S. Zhukov, A. Iones, G. Kronin, Eurographics 1998
    “First paper on ambient occlusion, AFAIK. Not that old…”

A GLSL version of smallpt

smallpt is a bare minimum path tracer written under 100 lines of C++, featuring diffuse, and specular reflection, and refraction. Using the detailed explanation slides by David Cline, I experimented porting it to GLSL on Shadertoy.

This proved to be an interesting experiment that brought a few lessons.

You can see the shader and tweak it here. By default it uses 6 samples per pixel, and 3 bounces, which allows it to run smoothly on average hardware. I found 40 samples per pixel and 5 bounces to give nice results while maintaining interactive framerate.

Path tracing, 40 samples per pixel, 5 bounces

Path tracing, 40 samples per pixel, 5 bounces

Update: since GLSL Sandbox has a feature, reading from the previous frame buffer, that Shadertoy is missing at the moment, I thought it’d be interesting try it to have the image converging over time. A little hacking later, a minute or so worth of rendering got me this kind of result: Given the effort, I am really pleased by the result.

Path tracing, 40 samples per pixel, 5 bounces

Path tracing, unknown number of samples per pixel, 7 bounces

A raytracer under a hundred lines of C++

On his website Kevin Beason presents a Monte Carlo ray tracer written with 99 lines of C++, generating a picture of a Cornell box with global illumination. Beyond the interesting experiment and the fact it can generate a binary of 4kB, I find very valuable the fact there are slides explaining all the code.