January 2009

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Daniel Pohl has a new article at his site about his efforts to ray trace the game Quake Wars at interactive rates. This article is not heavy-duty, and has some interesting tidbits and visualizations. For example, it turns out that cut-out textures (used for making trees, for example) are pretty expensive for his ray tracer. The problem is that a new ray must be spawned after each intersection is detected. The headache for ray tracing (at least in this system) is that the texture itself is not accessed at the time of intersection – deferred shading, essentially. So the ray tracer does not know that the ray has, in fact, not hit anything (i.e., hit a fully-transparent texel) and could continue unaffected. He also talks about other optimizations that have helped and might help in the future.

What I find exciting about Daniel’s work is that he’s working with data that was optimized for rasterization, not for ray tracing. If ray tracing was suddenly 10x faster than GPU rasterization with existing hardware in, say, DirectX 11 (keep dreaming), it wouldn’t matter that much in the short-term. For most companies there’s a lot of investment in training, workflows, and tools for producing games. For example, look how long it took normal mapping to become a mainstream feature, well after all new GPUs could support it (around 2002 with SM 2.0). So, ray tracing existing models I see as useful for determining whether ray tracing is feasible for current games, while also finding pain-points (such as cutout textures) that will be present in artist-generated content for some time to come.

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I Get Your Fail

This is great, a blog dedicated to strange and amusing bugs seen by game developers: http://igetyourfail.blogspot.com/

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Time to clear the collection of links and tidbits.

First, two new graphics books have come to my attention: Essentials of Interactive Computer Graphics and Computer Facial Animation, Second Edition. The first is an introductory textbook for teaching, well, just that. Real-Time Rendering was never meant as an introduction to the field of interactive graphics, we’ve always seen it as the book to hit after you know the basics. The Essentials book is squarely focused on these basics, and is more event-oriented and application-driven: GUIs and MFC, instancing and scene graphs, the transformation pipeline. It’s truly aimed at computer graphics in general, not 3D lit scenes. Shading is barely mentioned, for example. The book comes with a CD of software libraries developed in the latter half of the book. See the book’s website for much more information and supplemental materials (e.g. Powerpoint slidesets for teaching from the book!).

Computer Facial Animation is an area I know little about. Which makes this book intriguing to page through -how much there is to know! The first few chapters are dedicated to anatomy and early ways of recording facial expressions. The rest covers all sorts of areas: speech synchronization, hair modeling, face tracking, muscle simulation, skin textures, even photographic lighting techniques. This is one I’ll leave on my desk and hope to pick up at lunch now and again (along with those other books on my desk that beg to be read, like Color Imaging - I need more lunches).

Which reminds me of this nice talk by Kevin Bjorke: Beautiful Women of the Future. The first half is more aesthetic with some interesting fact nuggets, the last half is a worthwhile overview of interactive skin and hair rendering techniques.

It’s worth noting that there are many computer graphics books excerpted on Google Books. Our portal page, item #6, lists a few good ones.

Game Developer Magazine’s Front-Line Award Winners have been announced. Our book was nominated, but to be honest I’m not terribly upset it didn’t win (our second edition won it before); instead, a new book on (video)game design got the honors in the book category, The Art of Game Design. The rest of the award winners are (almost) no doubt deserving, but the winner list provides little new information. It’s the usual suspects: Photoshop CS3, Havok, Torque, Visual Studio 2008 (really? I’d go with Visual Assist X, which adds a bunch of useful bits to VS 2008 to make it more usable). I haven’t seen the Game Developer article itself, which should be more interesting to see the list of runner-ups.

Update: it’s a day later, and the Front Line awards article is available online. Good deal!

I just noticed that Jeremy Birn has been having lighting contests for synthetic scenes. Meant more for the mental ray users of the world, I like it just because there are some nice models to load up in my test applications.

We mentioned SIGGRAPH Asia before; see the papers collection here and some GPU-specific presentations here.

A fair bit going on in the blogosphere:

  • Christer Ericson has an article on optimizing particle system display. I hadn’t considered some of these techniques before.
  • Bill Mill has a worthwhile rant on publishing code along with research results. This often isn’t done, because there’s little benefit to the author. Some researchers will do it anyway, for various reasons (altruism, fame, etc.), but I wish the research system was structured to require such code. It’s certainly encouraged for the journal of graphics tools, for example, but even then the frequency is not that high.
  • Wolfgang Engel has lots of posts about programming for the iPhone & Touch; I was more interested in his comments about caching shadow maps.

Everyone should know about the Steam Hardware Survey. The cool thing is that they recently started adding a history for some stats and, dare I dream it?, pie charts to the site. Much easier to grok at a glance.

Tutorials galore:

Need a huge (or medium, or small), free texture of the whole earth? Go here.

Google’s knol project collects short articles on various topics. Here’s a reasonable sample: a short history of theories of vision. To be honest, though, the site overall seems a bit of a dumping ground. This sort of lameness is proof why editorial supervision (either a single person or a wiki community) is a good thing.

DirectX 10 corrects a long-standing “feature” of previous versions of DirectX: the half-pixel offset. OpenGL’s always had it right (and there really is a right answer, as far as I’m concerned). I was happy to find this full explanation of the DirectX 9 problem on Microsoft’s website.

Our book had a little review in the February 2009 issue of PC-Gamer, by Logan Decker, executive editor, on page 80. I liked the first sentence: “I don’t know why I didn’t immediately set fire to this reference for graphics professionals the moment I saw all the equations. But I actually read it, and if you skip the math bits as I did, you’ll get brilliantly lucid explanations of concepts like vertex morphing and variance shadow mapping—as well as a new respect for the incredible craftsmanship that goes into today’s PC games.”

This one’s made the rounds, but just in case: the Mona Lisa with 50 semi-transparent polygons, evolved (sort-of). Here’s a little eye candy (two links). Plus, panoramas galore.

Finally, guard your dreams.

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So I had such plans for all the things I’d get done during the holiday break. Well, at least I fixed our bathtub faucet, and kept the world safe from/for zombies in Left4Dead versus mode.

In contrast, Wolfgang Engel, Jack Hoxley, Ralf Kornmann, Niko Suni, and Jason Zink did something nice for the world: gave us a DirectX 10 book for free online. There’s more information about it at the site hosting it, gamedev.net. To quote Jack Hoxley, “It’s more of a hands-on guide to the API at a fairly introductory/intermediate level so doesn’t really break any new ground or introduce any never-seen-before cool new tricks, but it should bump up the amount of D3D10 content is available for free online.”

There are some great topics covered, including a thorough treatment of shading models, lots about post-processing effects, and an SSAO implementation (which I disagree with their specific implementation a bit in theory – convex objects shouldn’t really have self-shadowing ever, that’s why you usually ignore half the samples that are obscured, as a start – but SSAO is so hacky that it should be considered an artistic effect as much as photorealistic one). Lots of chewy stuff here.

Don’t be fooled because the book is only on the web, by the way. This is a high-quality effort: well-illustrated, the sections I sampled were readable and worthwhile, and there are solid code snippets throughout. The authors didn’t work out a print deal that they liked, so released the book to the web. You can see its original listing on Amazon. To quote Jack again, “We’re all glad it’s now out … for everyone to use.”

If you find errors or problems in the book, please let the authors know – the whole book is on a wiki, so you can add discussion notes (note: I found the wiki doesn’t work well with Chrome, but Internet Explorer worked fine). As the gamedev.net article notes, this release may form the basis of a book on DirectX 11, so could be considered something of a free beta. Please do reward the authors for their hard work by contributing feedback to them.

Update: Do keep in mind that this is a first draft (i.e., cut them some slack). Reading more bits, quality varies by section. I trust the authors will read and fix each others’ work as time goes on. I do like the wiki element. For example, there are some comments from Greg Ward in the corresponding discussion page for the implementation of the Ward shading model that should help improve their text.

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