level of detail

All of the hoopla regarding the game LittleBigPlanet has reminded me of the excellent talk that Alex Evans, co-founder of game creator Media Molecule, gave last year at the Advanced Real-time Rendering for 3D Games course at SIGGRAPH 2006. There are good presentation slides in PDF form at the ATI Developer site: here. If you look at the slide pictures you can see early renders of LittleBigPlanet characters, with unfortunate spheres places on their heads so as not to spoil the game (this was about nine months before the game was announced).

Anyway, he discusses a few techniques that he tried in achieving global illumination-like effects in a “small world” type of environment, all of which were implemented on a Radeon mobility 9800; nothing is too high tech.

Christer Ericson at the realtimecollisiondetection blog put up a well-written little post about why it’s ok to totally fake everything. In his case, he is referring to AI, but I like to this think this way about graphics (specifically, lighting) too. Recommended reading!

Appear smarter by moving in the right circles 

Abstract

This thesis will examine how a large water surface can be rendered in an efficient manner using modern graphics hardware. If a non-planar approximation of the water surface is required, a high-resolution polygonal representation must be created dynamically. This is usually done by treating the surface as a height field. To allow spatial scalability, different methods of “Level-Of-Detail” (LOD) are often used when rendering said height field. This thesis presents an alternative technique called “projected grid”. The intent of the projected grid is to create a grid mesh whose vertices are even-spaced, not in world-space which is the traditional way but in post-perspective camera space. This will deliver a polygonal representation that provides spatial scalability along with high relative resolution without resorting to multiple levels of detail.

This thesis was written in 2004 but never ended up getting published anywhere. I’ve seen it referenced a few times on message boards, etc. and in fewer papers, most recently the Wave Particles paper at SIGGRAPH 2007. It’s a great idea that I’ve come back to a few times, but I always have trouble dredging up the paper because of the vague title “Real-time Water Rendering”. For my own reference, and maybe yours too, I’m posting the link here.

Johanson, C. “Real-time Water Rendering” Paper + images + demo + source

John Carmack from id recently brought his virtualized texture technology back into the spotlight at QuakeCon 2007 (videos 1 2 3). Personally I think the concept of rolling your own texture virtualization and swapping in and out 80+GB of textures is immensely interesting. Especially when you factor in ideas like only fetching lower mip levels when you’re moving quickly and applying motion blur. There is a thread on gamedev.net right now that has lots of speculation and interesting ideas regarding how exactly to go about doing such a thing.

Also, the same thread linked to an interesting paper (“Unified Texture Management for Arbitrary Meshes”) from 2004 exploring some similar ideas.

Obviously my daily reporting of SIGGRAPH did not work out as planned. There were way too many things going on for me to be updating the blog daily. I am now home and will be pulling highlights from the conference for discussion here. In the meantime, you can check out what Leo Hourvitz had to say about the last few SIGGRAPHs. Very detailed notes make for an interesting read.

This blog will take a more personal slant for the next few days. I want to try and do daily updates on SIGGRAPH. It’s early in the morning of Day 1. I’m preparing to go register and attend the first course of the day. I believe I will attend the Pixar course “Anyone Can Cook”. It looks to cover lots of tidbits about food rendering and lighting techniques/choices they used in the movie. I was also interested in the Photon Mapping course by Wann Jensen but offline techniques are probably less applicable to me in everyday work. In the afternoon I think I will catch the last half of “State of the Art in Massive Model Visualization” or “Practical Least-Squares for Computer Graphics”.

I believe I’ll update this evening after the Fast Forward session and encourage anyone at the conference who happens to read this to post their 1st day experience too!