July 2011

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I think I need to pop my head out of my gopher-hole more often and see what my company’s doing. It turns out Autodesk software – including Maya, 3DS Max, Mudbox, AutoCAD, and everything else – is now free to students and educators. Just register and you’re good to go. Wow, this is a big change from the old system, and is definitely great to see.

There are also a number of betas from Autodesk free to anyone: one is 123D, a modeler that is aimed to help out the Maker crowd and 3d printing. I’ve installed this but haven’t played with it yet.

Another project is Photofly 2.0, where you upload a number of images and it makes a 3D model from the data (i.e., photogrammetry). This is similar to My3dScanner. I tried these two out on a set of photos of a bunch of bananas, some taken with a flash and some without, a hard test case. I definitely didn’t follow the guidelines. My3dScanner threw up its hands, Photosynth’s point cloud was incomprehensible, Photofly gave it a sporting chance, getting a cloud and making a mesh – no magic bullet yet, but fun to try. I’m now even tempted to RTFM, as results were better than I thought.

Photosynth (examine set of photos here):

Photofly’s cubist rendering – it did output an interesting Wavefront OBJ model:

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The SIGGRAPH 2011 papers were recently made available in the ACM Digital Library (see here). Although I recommend using Ke-Sen’s excellent papers links page when possible (it links to the freely accessible author copies and often to additional information provided by the authors), not all authors have chosen to make their papers available in this way. The Digital Library itself is pretty expensive (unless you’re a full-time student – see below), but if all you want is the SIGGRAPH stuff (including other conferences sponsored by SIGGRAPH), then a SIGGRAPH membership can get you access. SIGGRAPH memberships are only $42 ($30 for students, but students can get full Digital Library access with an ACM student membership for $42, which looks like a better deal).

In addition, for the first time ACM has published a document which includes the first page of each paper – kind of a paper version of the SIGGRAPH Papers Fast-Forward. This document is freely accessible here, and should be useful for people who just want to skim the papers program and see which papers to read in full. Be warned that the document is a bit large though (184MB). The video preview of the papers program might also be of interest (note that it only covers a few of the papers).

[Eric chiming in: here’s the link for how to access the Digital Library if you’re a SIGGRAPH member. Note that you can access all issues of ACM TOG as well as all SIGGRAPH-sponsored conference material and journals, not just SIGGRAPH, which is just about everything you’d want for graphics conferences: I3D, HPG, EGSR, NPAR, etc. Also, remember that the cool kids say SIG-GRAPH, not SEE-GRAPH.]

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The harddrive on my main computer died, which has the odd effect of making me have more time for blogging (and less for screwing around on random stuff). So, seven things:
  • First, if you’re going to HPG 2011, I’ll save you five minutes of searching for where it is: it’s at the Goldcorp Centre for the Arts, Google map here. Note also that things don’t start until 1:30 on Friday.
  • SIGGRAPH parties? I know nothing, except that the official SIGGRAPH reception is 9 to 11 PM Monday at the convention center, and the ACM SIGGRAPH Chapters Party is 8:30 PM to 2 AM on, oh, Monday again. Odd scheduling.
  • Timothy Lottes cannot be stopped: FXAA 3.11 is out (with improvements for thin lines), and 3.12 will soon appear. Note that the shader has a signature change, so your calling shader code will have to change, too.
  • At the Motorola developer site there’s a quick summary of various image compression types used for mobile phones and PCs.
  • Sebastien Hillaire implement the God Rays effect from GPU Gems 3, showing results and problems. Code and executable available for download.
  • I’ve been enjoying some worthwhile articles on patents and copyrights lately, both new and old. Worth a mention: Myrhvold madnessa comic (a bit old but useful) on copyright – a good overview; The Public Domain, a free book by a law professor who helped establish Creative Commons; the July 2011 CACM (behind the paywall, though) had a nice article on why the U.S. dropped “opt-in” copyright back in 1989 (blame Europe). Best idea gleaned, from The Public Domain: the length of copyright is meant to motivate people to create works for payment, so a retroactive increase in the length of copyright  (e.g., to protect Mickey Mouse) makes no sense – it creates no motivation for works already created.
  • Polygon Pictures’ office corridor would be a bad place to be if you worked way too many hours. Otherwise, nice!

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Eric has done these until now, but I now find myself with a few small things that fit well into such a post.

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The call for participation for the “OpenGL Insights” book ends in a month. If you have a good tutorial or technique about OpenGL that you’d like to publish, please send on a proposal to them for consideration.

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This is the third and last in a series of posts about the SIGGRAPH 2011 Talk program – see Part 1 and Part 2. If you found these useful you may also want to check out my previous series of posts about the SIGGRAPH 2011 Courses program (see Part 1, Part 2, Part 3, and Part 4). These posts are not intended as a general SIGGRAPH survey – they are focused on content related to real-time rendering and game development.

Show Me The Pixels

Three of the talks in this session have possibly relevant content:

  • Slow Art With a Trillion Frames Per Second Camera – I guess this one stretches the definition of “relevant” somewhat, but I just find it extremely cool and interesting. The talk describes some research done at MIT (in collaboration between the Media Lab and Department of Chemistry) in which a “trillion frames per second camera” captures how pulses of light travel within a scene, including bouncing off surfaces and scattering inside objects. Besides the general coolness factor, this may impart some insight into light behavior which could be useful when working on shading and lighting models.
  • Device-Independent Imaging System for High-Fidelity Colors – color management (including display calibration, color space management of data, etc.) is important for both game and film production. It turns out that getting good device-independent color reproduction is far from simple. This talk covers some advances in this field by SHARP Corporation and Shizuoka University.
  • Who Do You Think You Really Are? – augmented reality is becoming an important technology for handheld games (see examples on the Nintendo 3DS and iPhone); this talk discusses an interactive media installation at London’s Natural History Museum (in partnership with BBC Television) which includes augmented reality elements.

Hiding Complexity

This entire session is comprised of game industry talks:

  • Occlusion Culling in Alan Wake – occlusion culling is a key technology for many games, especially first-person shooters. This talk discusses the occlusion culling system (developed by Umbra Software) used in the game Alan Wake by Remedy Entertainment. Topics include visibility culling as well as shadow-caster culling for dynamic light sources.
  • Increasing Scene Complexity: Distributed Vectorized View Culling – another talk on visibility culling, this time focusing on the technical issues involved in parallelizing culling computations on current game platforms. The talk is given by Electronic Arts Blackbox.
  • Practical Occlusion Culling in Killzone 3 – the third occlusion culling talk of the session focuses on the implementation used by Guerrilla Games for the game Killzone 3. This implementation uses PlayStation 3 SPUs to rasterize a conservative depth buffer, against which occlusion queries are performed.
  • High-Quality Previewing of Shading and Lighting for Killzone 3 – another Killzone 3 talk but unrelated to occlusion culling, this talk by Guerrilla Games covers a content creation framework which supports high-fidelity previews of assets in Autodesk Maya.

Smokin’ Fluids

The talks in this session (three from the film industry and one from the academic research community) cover topics related to smoke and fluid simulation. Such simulations are currently too costly to be feasible for most games, though games such as the LittleBigPlanet and PixelJunk Shooter series (both featured at SIGGRAPH this year) include two-dimensional versions. In VFX and CG animation work smoke, fluid and fire simulations are common, forming one of the key elements differentiating film and game visuals. I firmly believe that as game platforms increase in computational power, we will start seeing full 3D simulations of this kind in games.

  • DB+Grid: A Novel Dynamic Blocked Grid For Sparse High-Resolution Volumes and Level Sets – The author, Ken Museth, has a history of developing novel data structures for level set and volumetric data and applying them for VFX, first at Digital Domain and now at DreamWorks Animation. His data structures have been constantly improving, from DT-Grid to DB-Grid and now DB+Grid, which is described in this talk.
  • Capturing Thin Features in Smoke Simulations – In production simulation work, there is a constant tension between the need to speed up simulation times for faster iteration (which implies reducing the resolution of the simulation grid) and the desire to simulate finer detail (which implies increasing the resolution). This talk covers a system developed by Sony Pictures Imageworks that allows thin smoke features to be captured even with low resolution simulation grids.
  • Implicit FEM and Fluid Coupling on GPU for Interactive Multiphysics Simulation – typically distinct simulation methods are used for fluids, rigid objects, deformable objects, etc. This can pose problems when different types of objects can affect each other, which requires coupling different simulation methods. This talk from INRIA and Université de Grenoble covers a GPU-based method for coupled simulation of deformable objects and fluids – interestingly “screen-space collision” is mentioned as one of the techniques employed.
  • Correcting Low-Frequency Impulses in Distributed Simulations – production rendering is typically distributed over a large number of machines. It is desirable to do the same for simulations, but often this is difficult since the simulation domain is not easily separable – each part of the simulation affects all other parts. This talk from Side Effects Software (developers of Houdini) describes a method for distributing level-set fluid simulations while keeping them coupled via a shared low-resolution pressure projection.

Volumes and Rendering

All four talks in this session (three from the film industry and one from the academic research community) contain potentially relevant content:

  • Gaussian Quadrature for Photon Beams in “Tangled” – rendering lighting effects in participating media (often called “light beams” or “god rays”) is a common problem in games and film, typically solved with various hacks. A recent Transactions on Graphics (ToG) paper presented a comprehensive analysis of the problem as well as a new rendering approach called “photon beams” which is both physically correct and efficient – it appears potentially feasible for real-time implementation. This talk (with authors from the University of Central Florida, Disney Research Zürich, and Walt Disney Animation Studios – including the first author of the aforementioned ToG paper) presents an efficient implementation of the photon beams technique in Renderman, extending it to artist-specified non-physical light attenuation curves. A broader overview of the artist-driven volumetric lighting in Tangled (of which this work is a part) is given in a Technical Paper.
  • Importance Sampling of Area Lights in Participating Media – in principle, ray tracers like the Arnold rendering engine (developed by Solid Angle SL and used by Sony Pictures Imageworks, among others) solve the participating media lighting problem in a straightforward manner by sampling the underlying integrals. In practice, achieving noise-free images in reasonable time requires a lot of engineering effort, mostly relying on various forms of importance sampling. This talk (with authors from both Solid Angle and Imageworks) presents an importance sampling method for single scattering of light from arbitrary area lights in homogeneous participating media.
  • Decoupled Ray Marching of Heterogeneous Participating Media – after two talks on the relatively easy problem of lighting homogeneous participating media, this talk (also from Sony Pictures Imageworks) covers heterogeneous media such as smoke. It covers a method for speeding up ray marching by decoupling lighting calculations from the sampling of volume properties. Ray marching is amenable to real-time implementation since it is easy to scale down (albeit with reduced visual quality) by reducing the number of samples – several companies have demonstrated real-time implementations (though I’m not sure if any shipping games yet use it). The technique presented in this talk can make raymarching for volumetric lighting even faster, so is definitely of interest.
  • Demand-Driven Volume Rendering of Terascale EM Data -unlike the other talks in this session which focus on volumetric lighting, this talk (from King Abdullah University of Science and Technology and Harvard University) focuses on a different issue – rendering volumetric datasets which are too large to fit in memory. Given a good solution to this problem, games should be able to precompute volumetric effects in certain situations and stream them from disk, so this looks interesting.

Heads or Tails

Rigging game or movie characters for animation is a very tricky problem – the rig needs to be powerful enough to handle all needed motions and deformations, while also being easy to control either via hand-keying or motion capture. This session includes two CG feature animation talks and one research talk, all covering the rigging problem from different angles (note that the game industry talk Modular Rigging in Battlefield 3 has been cancelled). Character rigging is one of the areas where film and game production are quite similar – there are differences in scale and complexity, but even these are not so large as differences in say, triangle count or shader instructions.

  • Building the Birds of “Rio” – this talk covers the process and technology used at Blue Sky Studios to build control systems for the bird characters in the movie Rio – using the main character “Blu” as a case study.
  • “Kung Fu Panda 2″: Rigging a Peacock Tail – this talk describes the approach DreamWorks Animation used to create the tail rig for the peacock character in the film Kung Fu Panda 2.
  • Optimized Local Blendshape Mapping for Facial-Motion Retargeting -this talk from the Graphics Lab at the USC Institute for Creative Technologies details an automatic facial-motion retargeting method for blendshapes.

Speed of Light

Three of the talks in this session contain potentially relevant content:

  • Run-Time Implementation of Modular Radiance Transfer – Precomputed Radiance Transfer is a powerful rendering technique which has spun off many variations. This talk from Disney Interactive Studios, Disney Research Zürich, the University of Utah and the University of North Carolina at Chapel Hill covers a modular variant which enables warping and combining precomputed transport from a small library of simple shapes. The technique was implemented for platforms from mobile devices to high-end GPUs – the talk discusses various implementation issues involved.
  • Next-Generation Image-Based Lighting Using HDR Video – image-based lighting is becoming a key rendering technique in both film and games. This talk from Linköping University and Spheron VR describes a system for high-dynamic-range video capture, reconstruction, and modeling of real-world scenes for use in image-based lighting of synthetic objects placed in the scene.
  • Triple Depth Culling – real-time rendering applications such as games rely heavily upon hardware features such as hierarchical Z-culling for performance. However, this has some drawbacks – it requires either depth sorting or a previous depth prepass, and it doesn’t work well with shaders that modify depth. This talk proposes a technique to avoid these drawbacks – the authors show a pixel shader implementation, though for best performance they suggest that the technique be implemented in hardware. The talk abstract and video are both available online.

Capture and Construction

This session has one film talk of relevance: Building and Animating Cobwebs for Antique Sets. It describes a workflow used at DreamWorks Animation to model and animate cobwebs, including a specialized modeling tool, a physics-based solver, and a procedural-modeling engine. These types of specialized asset workflows can be extremely effective for games or movies which require many examples of a given kind of asset.

Light My Fire

This session has one game talk, as well as three relevant film talks:

  • Simulating Massive Dust in “Megamind” – in film production, there is a constant push for fluid simulations to continually increase in size and complexity, but the need for fine control by artists implies fast turnaround times. For this reason a lot of research and development is spent on making these simulations faster – research that I hope will eventually benefit real-time applications as well. This talk from t DreamWorks Animation covers a fast fluid simulation framework used for the movie Megamind. The presentation covers the specific numerical methods used to ensure efficiency and quality, as well as the setup and control framework that allowed artists to work efficiently.
  • “Megamind”: Fire, Smoke, and Data – another Megamind talk, this time focusing on the specific case study of an especially large and involved explosion effect. I like attending such “war story” talks – the most interesting film and game work is done when trying to push boundaries, and the solutions are often a mixture of technical cleverness and artistic inspiration.
  • Volumetric Effects in a Snap – grid-based simulation and volumetric rendering frameworks have become a staple of VFX and CG feature animation work; every studio has its own system with different strengths. I suspect similar systems will start cropping up in game studios when the hardware becomes a bit faster and memory capacities increase a bit more. This talk describes the creation of the “Snap” system developed at Animal Logic and used in the films Legend of the Guardians: The Owls of Ga’Hoole and Sucker Punch.
  • Fluid Dynamics and Lighting Implementation in PixelJunk Shooter 2 – games rarely incorporate fluid simulations – including 2D games, though current platforms can run two-dimensional simulations quite quickly. LittleBigPlanet notably incorporated 2D fluid simulations in its fire and smoke effects, but these did not affect gameplay. The game PixelJunk Shooter incorporated some very nice fluid-simulation-driven gameplay, including several types of fluids and gases that affected each other in different ways. The recent sequel expanded this gameplay element, adding some novel light/darkness gameplay as well. This talk from independent developer Q-Games covers the technical aspects of these elements.

Now that I’ve finished the courses and talks, my next few blog posts will cover the remaining SIGGRAPH 2011 programs.

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This is the second in a series of posts on the SIGGRAPH 2011 Talk program – Part 1 can be found here. These posts focus on talks with relevant content for real-time rendering researchers and practitioners, including game developers.

Building Blocks

One of the talks in this session looks relevant – KinectFusion: Real-Time Dynamic 3D Surface Reconstruction and Interaction describes the use of a Kinect camera to acquire real-time dense 3D models of an entire room and its contents, enabling some interesting augmented reality and interaction possibilities. The reconstruction appears to require a high-end GPU to achieve real-time performance so this isn’t something for current generation consoles, but it definitely could be feasible on future platforms. It may also be interesting in the context of digitizing real-world objects as part of the film or game modeling process. The authors are from Microsoft Research Cambridge, except for one from Imperial College London.

Walk the Line

Two academic research talks in this session are potentially relevant for games and other real-time applications that use stylized rendering or deformations:

  • Parameterizing Animated Lines for Stylized Rendering – this talk describes a paper from the 2011 NPAR (Non-Photorealistic Animation and Rendering) conference (which is co-located with SIGGRAPH this year). It shows a way to have details along an outline track the geometry cleanly as the scene animates in 3D. Material from the NPAR paper can be found here. The authors are from École d’Ingénieurs Télécom ParisTech, except for one from Adobe.
  • Multiperspective Rendering for Anime-Like Exaggeration of Joint Models – this talk describes a more unusual type of stylization, where the model deforms in a stylized way as it animates, inspired by anime visual conventions. The authors are from Hitachi, except for one from The University of Tokyo.

1000 Points of Light

This session contains one game talk, as well as two relevant CG feature animation talks:

  • Lighting Tokyo for Pixar’s “Cars 2″ – rendering cities at night is challenging (definitely for games, but even for CG feature animation) due to the extreme dynamic range and large number of lights. Tokyo, with its massive quantities of illuminated billboards and neon signs, is one of the most famous and extreme examples of this type of lighting situation. This talk covers the techniques used by Pixar Animation Studios to light a stylized version of nighttime Tokyo for the movie Cars 2 – note that the speaker will also present a Studio Talk on a similar topic.
  • “Megamind” – Lighting Metro City at Night – this task covers a similar challenge as the previous one, but with a distinct set of solutions from a different company (DreamWorks Animation) for a different film (Megamind).
  • Deferred Shading Techniques Using Frostbite in Need for Speed The Run – this talk will cover the tile-based deferred lighting architecture used in the Frostbite 2 engine, with emphasis on the PS3 implementation as used in the Electronic Arts game Need for Speed The Run (the talk was originally intended to cover the XBox 360 and Battlefield 3 as well, but has been refocused – the removed material will be covered in more depth in this course). It makes for an interesting combination with the previous two talks since it will show how the current state-of-the-art in game technology solves a similar problem as film (albeit at smaller scale) in real time.

Fur and Feathers

The three CG feature animation talks in this session cover fur and feather techniques which are too computationally costly to be feasible for most real-time applications today. They also don’t seem amenable to “animation baking” precomputation approaches since the resulting data would most likely be too heavy. However, these techniques should be able to run in real-time on future hardware platforms, making these talks of interest to forward-looking real-time researchers:

  • Quill: Birds of a Feather Tool – this talk describes a specialized pipeline developed by Animal Logic to procedurally model, animate and simulate feathers while avoiding intersections and rendering at various levels of detail.
  • Dynamic, Penetration-Free Feathers in “Rango” – somewhat similar to the previous talk, but focusing more narrowly on interpenetration avoidance and from the perspective of a different company (Industrial Light and Magic).
  • Accurate Contact Resolution for Interpolated Hairs – another ILM / Rango talk, but focusing on a different problem – handling collision between hairs and other geometry. The solution needed to be very fast and cheap since it was intended for use on interpolated hairs (it is common in CG feature animation and VFX to fully simulate a relatively small number of “guide hairs” and then interpolate a much larger number of cheap “interpolated hairs” between them).

Mixed Grill

This session contains two film talks, one game talk, and one academic research talk; all four are relevant:

  • The Power of Atomic Assets: An Automated Approach to Pipeline on “Legend of the Guardians: The Owls of Ga’Hoole” – games and movies share the challenge of structuring a production pipeline (software tools as well as workflow practices) to handle large numbers of assets. This talk will describe the system used at Animal Logic to handle the assets for the film Legend of the Guardians: The Owls of Ga’Hoole.
  • Animation Workflow in Killzone 3: A Fast Facial Retargeting System for Game Characters – handling facial motion capture data is tricky, especially retargeting to (possibly multiple) in-game models. This talk describes a technique used by Guerrilla Games to animate a large number of different faces for the extensive cut-scenes in the game Killzone 3.
  • Adaptive Importance Sampling for Multi-Ray Gathering – importance sampling (basically sampling a function more densely in areas that are estimated to have higher impact on the result) has recently become a key technology for production rendering. There was a whole SIGGRAPH course about it last year, and Pixar has added native support to the latest version of Renderman. Importance sampling is typically thought of as a ray tracing technique, but it is also important for image-based lighting (IBL) sources such as environment maps. Importance-sampled IBL is currently useful for game light baking tools, and is likely to be done in real-time on future platforms. This talk describes importance sampling improvements developed at Rhythm & Hues. Talk materials including an abstract and movie are available here.
  • High-Resolution Relightable Buildings From Photographs – efficient digitization of real-world scenes and objects is useful for both film and game development. Tools such as Crazybump are widely used in the game industry to infer relightable surface details from photographs, but do not always work as well as could be hoped. This research talk looks like it could offer some improvements in this area, making it of wide interest. The authors are from The University of Manchester, Loughborough University, and Dolby Canada.

From the Ground Up

All three CG feature animation talks in this session are relevant for game developers:

  • We Built This City: Big City Design and Implementation in “Kung Fu Panda 2″ – games and movies sometimes contain large urban environments, which are very difficult to construct within reasonable time and staffing constraints. This talk will detail how DreamWorks Animation solved this problem for the film Kung Fu Panda 2.
  • The Visual Style of “Legend of the Guardians: The Owls of Ga’Hoole” – finding a good visual style is another difficult task shared by film and games; my feeling is that films tend to have more established processes for look and style development. This talk will detail the visual style established by Animal Logic for the movie Legend of the Guardians: The Owls of Ga’Hoole. I saw a similar presentation at FMX 2011, and it was full of interesting and relevant content.
  • Clouds in the Skies of Rio – in most games and films, clouds are off in the distance and can be handled with straightforward methods. But sometimes the camera needs to get up close and personal with the clouds, which can pose some interesting modeling and rendering challenges. Although cloud rendering techniques used in film can rarely run in real-time on current platforms, the way in which the clouds are art-directed and authored can be of interest. This talk discusses how Blue Sky Studios handled cloud authoring and rendering for the movie Rio.

Directing Destruction

Mixing simulation with manual control to create large, physically-believable and art-directed effects is a tough challenge which VFX and CG feature animation professionals have been focusing on for some time. The techniques used rarely lend themselves to real-time computation on current hardware. However, in many cases these effects can be pre-computed, and on future hardware they are likely to run in real time (perhaps with some reduction in scale). The four talks in this session discuss various case studies of this type:

  • End of Line: Character Destruction in “Tron: Legacy” – this talk discusses the tools developed by Digital Domain for the character destruction effects in Tron: Legacy.
  • Kali: High-Quality FEM Destruction in Zack Snyder’s “Sucker Punch” – in this talk, The Moving Picture Company discusses a finite-element simulation toolkit developed in partnership with Pixelux, with examples of its use in the film Sucker Punch. It is interesting to note that the tool is based on the same Digital Molecular Matter technology used in the games Star Wars: The Force Unleashed and Star Wars: The Force Unleashed II.
  • Directing Hair Motion on “Tangled” – this talk discusses the system developed by Walt Disney Animation Studios to animate the main character’s hair (almost a character in itself) in the movie Tangled.
  • Choreographing Destruction: Art Directing a Dam Break in “Tangled” – another Tangled talk from Walt Disney Animation, this one describes the way in which a complex water and rigid body simulation was art-directed for the “dam break” sequence.

Crowds

Scenes with large crowds are another differentiating factor between film and games. Sufficiently large crowds pose authoring and rendering challenges even for film; the solutions to these may be of interest to game developers working with smaller real-time crowds on next generation platforms. The three talks in this session discuss crowd case studies from three CG animated feature films:

  • Crowds on “Cars 2″ – this talk discusses how Pixar Animation Studios improved their production pipeline to enable higher productivity when managing assets and controlling agent behaviors for Cars 2 crowd shots.
  • Synthesizing Complexity for Characters and Landscapes in “Rio” – this talk covers the systems used at Blue Sky Studios to procedurally generate large varied crowds of people and flocks of birds for the movie Rio, as well as the renderer enhancements done to efficiently ray-trace the resulting massive geometric detail.
  • Staging Carnival: Ray Tracing Crowds in “Rio” – another Blue Sky Studios talk about Rio, this time focusing on a specific case study (the carnival crowds).

There are eight more Talk sessions with relevant content, which I will cover in a subsequent blog post.

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After summarizing the course program, I’ll continue going over content in other SIGGRAPH 2011 programs which may be of interest to game developers or real-time rendering researchers. Next up is the Talks program; this post will also be a multi-parter, since there is a LOT of content to cover in this program.

Update July 16, 2011: Added link to “Coherent Out-of-Core Point-Based Global Illumination” EGSR 2011 paper.

Talks (which used to be called “Sketches” a few years ago) are short presentations – 20 minutes long (rare “long talks” are 40 minutes). Talks are a lot “leaner” than Technical Papers, which require detailed analysis, comprehensive citations of previous work, and comparisons to competing techniques. For this reason, SIGGRAPH Talks tend to be the venue of choice for industry practitioners, who often have limited time to spend on writing publications.

The SIGGRAPH Talk program has historically been dominated by talks from the fields VFX and CG feature animation – many of these contain relevant information for game developers, but the game industry itself has been under-represented. SIGGRAPH 2011 has a record number of game industry Talks, but there is still a lot to go before we match the film people (I hope to get a lot closer in future years!)

I will now summarize relevant Talks regardless of speaker affiliation. Since Talks are scheduled in sessions of four I will organize my summary along the same lines, skipping sessions without any relevant Talks and using the session order from the SIGGRAPH 2011 Talks page.

Pushing Production Data

This session contains four film talks, all of potential interest:

  • Coherent Out-of-Core Point-Based Global Illumination describes a system used at DreamWorks Animation for computing global illumination and ambient occlusion- the details may be of interest to game developers working on “baking” precomputation systems. There is also an EGSR 2011 paper by the authors on this topic.
  • Similarly, the information in Destroying Metro City: An Artist-Friendly and Efficient Demolition Pipeline for “Megamind” (also from DreamWorks Animation) could be relevant for precomputation of destroyed and fractured versions of game assets.
  • The efficient digital acquisition of real-world props is a problem facing games as well as film; PhotoSpace: A Vision-Based Approach for Digiziting Props describes an interesting system used at Weta Digital for this.
  • Games and film development are not “one size fits all” – individual games and films often require specific assets which can benefit from specialized authoring and rendering systems. Artistic Rendering of Feathers for Animated Films (yet another DreamWorks Animation talk) describes such a system.

Facing Hairy Production Problems

This session contains one game talk and three relevant film talks:

  • Extensive use of geometry instancing is important in both games and film to save on asset authoring time and memory. The talk Kami Geometry Instancer: Putting the “Smurfy” in Smurf Village describes an instancing pipeline developed by Sony Pictures Imageworks which allows for distinct deformation of individual instances.
  • The talk Making Faces: Eve Online’s New Portrait Rendering describes the impressive new avatar portrait system developed by CCP Games for the Eve Online space MMO.
  • SpeedFur: A GPU-Based Procedural Hair and Fur Modeling System describes a hair modeling system (developed by Fido). The procedural authoring system and the GPU-accelerated preview mode both appear relevant for hair and fur in games.
  • The talk GPU Fluids in Production: A Compiler Approach to Parallelism details a specialized CPU/GPU parallel compiler for fluid simulation developed by Double Negative Visual Effects. New parallelism approaches are always interesting, and I suspect fluid simulation will be a major differentiating feature for games on the next generation of platforms.

Eye on the Road

Two of the talks in this session (one by game developers, and one by academic researchers) appear relevant:

  • MotorStorm Apocalypse: Creating Urban Off-Road Racing – this talk by Evolution Studios presents rendering and tools advances which enabled adding large-scale dynamic events to MotorStorm Apocalypse, the latest entry in the MotorStorm racing game franchise (also showcased in The Sandbox).
  • Facial scanning has been a topic of heightened interest in the game industry since its highly publicized use in L.A. Noire. The talk R&D Facial Cartography: Interactive High-Resolution Scan Correspondence (by Paul Debevec’s graphics lab at the USC Institute for Creative Technologies) covers some interesting advances in this area.

Tiles and Textures and Faces Oh My!

This session contains talks by game developers, CG feature animation professionals, and hardware vendors; all four are relevant:

  • Artist-guided procedural authoring systems can help with the asset creation issues faced by both game and film production. The talk Procedural Mosaic Arrangement In “Rio” details Blue Sky Studios‘ art-directable procedural pipeline for sidewalk and street tile mosaics.
  • Programmable tessellation is one of the primary features of DirectX11, but authoring content for it can be challenging. NVIDIA‘s talk Generating Displacement From Normal Map for Use in 3D Games describes one possible solution to this problem.
  • The film industry has found the open-source Ptex (per-face texture mapping) technology developed by Walt Disney Animation extremely useful for getting rid of UV layout issues. The talk Per-Face Texture Mapping for Real-Time Rendering (jointly presented by an NVIDIA developer technology engineer and the first author of the original Ptex paper) presents a real-time implementation of this technology.
  • Skinning is one of the most fundamental technologies in game rendering and has not changed much in the last twenty years. The talk Spherical Skinning With Dual Quaternions and QTangents presents some skinning improvements achieved by Crytek during development of the Crysis franchise.

Let There Be Light

This session contains three CG feature animation case studies, all with interesting information for game  developers:

  • I find Rango to be an intriguing case of live-action and VFX methods being used by Industrial Light and Magic to make a CG animated feature with a unique photorealistic style. The talk “Rango”: A Case of Lighting and Compositing a CG-Animated Feature in an FX-Oriented Facility appears to have some interesting information on the methods used by the lighting and compositing artists.
  • Ocean Mission on “Cars 2″ – this talk describes how Pixar addressed several multi-disciplinary challenges involving the ocean in the opening sequence of Cars 2.
  • Hair is another area where games lag noticeably behind film, so learning about film methods is valuable. The talk Untangling Hair Rendering at Disney details technology, tools and workflow advances adopted by Walt Disney Animation for the film Tangled.

Out Of Core

The four talks in this session are all relevant for game developers or real-time rendering researchers:

  • Google Body: 3D Human Anatomy in the Browser – this talk describes how Google used the WebGL API in an innovative way to create an impressive in-browser application. Browser-based games are a rapidly increasing market, making APIs such as WebGL important to many game developers. The Google Body application is also showcased in The Sandbox.
  • As a possible future alternative to the traditional rendering pipeline, ray tracing sparse voxel octrees has attracted some interesting research work, including GigaVoxels (several publications on which can be found on Cyril Crassin’s webpage). The talk Interactive Indirect Illumination Using Voxel Cone Tracing: An Insight builds on the GigaVoxels work to compute indirect lighting and ambient occlusion for complex scenes in real time.  A preview was presented as an I3D 2011 poster, and various materials relating to the SIGGRAPH Talk can be found on a dedicated web page.
  • Rendering the Interactive Dynamic Natural World of the Game: From Dust – in this talk, Ubisoft Montpellier discusses the simulation and rendering techniques used for the dynamic world of the game From Dust.
  • Out-of-Core GPU Ray Tracing of Complex Scenes -  this talk covers the CentiLeo GPU ray tracer (based on Kirill Garanzha’s PhD research at the Keldysh Institute of Applied Mathematics), which can render models composed of several hundred million polygons in real-time. More information on CentiLeo (including a video of it in action) can be found here.

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This is the fourth and last of a series of posts on the SIGGRAPH 2011 course program; each describing several of the courses that will be presented at the conference. Links to previous posts in the series: Part 1, Part 2, Part 3.

Cinematography: The Visuals & the Story

Cinematography is the art of communicating a story via camera and lighting choices. As a game developer, I find it fascinating for several reasons. One is that it is such a well-established art; over a century old, and based upon many of the principles of still older arts such as photography and painting. The maturity of the field can be seen in the way that the practice is codified – there are clear roles in film production, everyone knows what a director of photography, first camera assistant, etc. do from film to film. The field’s most prominent professional organization, the American Society of Cinematographers, was created in 1919 and its magazine American Cinematographer has been discussing tips and tricks of the trade since 1920. It’s an interesting contrast to game development – an extremely young discipline where most of the fundamentals are still being figured out.

Another reason I’m interested in cinematography is its relevance to game visuals; the primary problem (turning three-dimensional scenes into compelling screen images that carry a narrative) is the same. While issues of camera placement may be less relevant for some game genres (e.g. first person shooters), lighting, color, and scene composition considerations are relevant for almost any game.

The third reason is that most game developers (including myself until fairly recently) are either unaware of this vast wealth of relevant knowledge, or are indifferent to it. CG animated features have made great strides by incorporating principles of live-action cinematography; not many videogames are doing the same.

For these reasons, I’m glad to see a SIGGRAPH course covering cinematographic fundamentals. The speaker, Bruce Block, has had a lot of experience working in film (albeit not in the camera department) and has written a well-regarded and influential book (The Visual Story) about how visual structure is used to present story in film.

Storytelling With Color

The way in which color choices are applied throughout production is another area where I think games have a lot to learn from film. In film, the colors of almost every costume and piece of set decoration are part of a conscious choice to drive the narrative, establish a mood, or support character development. This was brought home to me last year when I visited Pixar and saw the “color script” for Toy Story 3 – a wall covered by postcard sized sketches, one for each shot in the film. Each rough sketch blocked out the shapes and colors in the shot, and when they were put together, you could clearly see how the carefully chosen color palette helped drive the story and emotional tone of the movie. Two of the Toy Story 3 color script images can be seen here, and the entire color script for a different Pixar film (Up) can be seen here.

This course will cover exactly these kinds of color choices, and will be presented by Kathy Altieri (Production Designer, Dreamworks Animation) and Dave Walvoord (Digital FX Supervisor, Dreamworks Animation). Kathy’s career in TV and film spans three decades; after working on backgrounds for multiple animated TV shows as well as classic animated feature films such as The Little Mermaid, Aladdin and The Lion King, she moved to Dreamworks, where she was Art Director on The Prince of Egypt and Production Designer on Spirit: Stallion of the Cimarron, Over the Hedge, and How to Train Your Dragon. Dave has 15 years of experience in VFX and CG feature animation, working at Blue Sky on films such as Fight Club and Ice Age before joining Dreamworks, where he was CG Supervisor on Shark Tale, Over the Hedge and Kung Fu Panda and Digital FX Supervisor on Kung Fu Panda 2.

Applying Color Theory to Digital Media and Visualization

This is another course on color, but focused more on theory and on non-entertainment applications, such as scientific visualization. The course is presented by Theresa-Marie Rhyne, a prominent visualization expert with three decades of experience as a researcher, educator, designer and artist. She has taught several courses on this topic, most recently at IEEE Visualization 2010 (a video of her slides from that talk is available online), and has a blog on the topic as well. Interestingly, she has already put up a video of the slides from the upcoming SIGGRAPH 2011 course.

Liquid Simulation With Mesh-Based Surface Tracking

While most fluid rendering and simulation work over the years has focused on level-set approaches, an important recent trend in this area consists of tracking a mesh over the surface of the fluid, thus enabling more detailed surfaces. This advanced course (prior knowledge of fluid simulation techniques is assumed) covers the current state of the art in this important area, and is presented by Chris Wojtan (Assistant Professor, Institute of Science and Technology Austria), Matthias Müller-Fischer (Research Lead, NVIDIA), and Tyson Brochu (PhD Candidate, University of British Columbia). Having performed much of the leading research in this area, the speakers are uniquely qualified to speak about the topic.

Although complex fluid simulations are used extensively in film VFX and animated features, they are currently too computationally expensive for games. As game platforms become more powerful, I believe this will change. There are already some impressive real-time demonstrations, for example the Raging Rapids Rides demo which will be shown at the SIGGRAPH 2011 Real-Time Live! program and the SIGGRAPH 2011 paper Real-Time Eulerian Water Simulation Using a Restricted Tall-Cell Grid, which has an impressive video here (check out the lighthouse part at the end). Note that one of the course speakers (Matthias) was involved with both of these examples.

Introduction to Modern OpenGL Programming

Dave Shreiner (co-author of the famous OpenGL Red Book, which has a new edition coming out this November) has taught an introductory course on OpenGL (almost) every year at SIGGRAPH since 1998. He was accompanied by various co-lecturers – most often Edward Angel – and evolved the course content to keep up with changes in the OpenGL API. The only two years Dave didn’t do this course were 2003 (when he  did a “performance OpenGL” course instead of an introductory course – in some other years he did both), and 2010 (when there was no OpenGL course for the first time since 1992). Dave and Edward are back this year with an updated course, which should be of great interest to beginning graphics programmers, OpenGL programmers who have been using older versions of the API, or experienced graphics programmers with plans to start working with OpenGL.

An course on this topic couldn’t hope for better speakers. Besides his highly influential books and courses, Dave Shreiner also had an important role in the development of OpenGL (and its spinoff OpenGL ES) in the 15 years he worked at SGI (where OpenGL evolved from the proprietary IRIS GL library) and since, as Technical Advisory Panel Chair for The Khronos Group and Director of Graphics Technology at ARM. Edward Angel has taught at the University of New Mexico for over 30 years; he holds the positions of Professor Emeritus of Computer Science and Founding Director of the Art, Research, Technology and Science Laboratory (ARTS Lab). Edward has written several influential books on computer graphics, most notably the OpenGL Primer and Interactive Computer Graphics.

Modeling 3D Urban Spaces Using Procedural and Simulation-Based Techniques

As scene complexity increases, the amount of artist work (and thus the expense) required to create these scenes increases commensurately, a problem that afflicts both film and game production. Audience expectations are always increasing, and budgets cannot keep pace – more efficient ways to model large, complex scenes must be found. While most natural scenes are very complex, techniques for procedurally modeling them have been used in production for some time; see off-the-shelf products such as Vue and Speedtree, or in-house tools such as were used to model trees in Tangled. Urban scenes can be as complex, but tools for modeling them procedurally have been less widely used (the creation of 1930′s New York City in the 2005 remake of King Kong is a notable example – more details here). The last few years have seen a flourishing of research into procedural modeling of buildings and cities, and the fruits of this research are finding their way into production. This course will cover procedural as well as image-based and simulation-based modeling techniques, and is targeted at applications including computer games, movies, architecture, and urban planning.

This course will have five speakers, each extremely well-suited to teach a course of this type: Peter Wonka (Associate Professor, Arizona State University), Daniel Aliaga (Associate Professor, Purdue University), Carlos Vanegas (Research Assistant, Purdue University), Pascal Mueller (Founder & CEO, Procedural Inc.), and Michael Frederickson (Technical Director, Pixar).The first four speakers have, between them, performed or led most of the notable academic research in this area. Pascal Mueller has founded a company (Procedural Inc.) based on his research, which sells a commercial software package (CityEngine) for procedural urban modeling (Peter Wonka serves on Procedural’s advisory board). The last speaker, Michael Frederickson, was responsible for modeling the 40,000 buildings in the city of London as seen in the movie Cars 2, and it appears that this will be the topic of his presentation. Presumably (given his participation in this course, and also given the magnitude of the task) this was done procedurally. While watching Cars 2 (story issues aside) I was struck by the visuals in the film – the urban environments, especially London, in particular; I look forward to finding out how this was done.

3D Spatial Interaction: Applications for Art, Design, and Science

This course will be taught by Joseph LaViola (Assistant Professor, University of Central Florida) and Daniel Keefe (Assistant Professor, University of Minnesota). Last year at SIGGRAPH 2010, Prof. LaViola taught (with Richard Marks, the primary researcher behind Sony’s EyeToy and Move peripherals), a course about spatial interaction with videogame motion controllers. This year’s course, judging by its abstract, appears to be focused on applications other than videogames. These novel interfaces surely have interesting applications in many fields, and this course will be of interest to many. Both Prof. LaViola and Prof. Keefe have done important research in this field, and Prof. LaViola has authored a book on the subject.

Build Your Own Glasses-Free 3D Display

Last year, two of this course’s speakers, Douglas Lanman (Postdoctoral Associate, MIT Media Lab) and Matthew Hirsch (PhD Student, MIT Media Lab), taught a SIGGRAPH 2010 course called Build Your Own 3D Display. This year, they are joined by Gregg Favalora (Principal, Optics for Hire) and are focusing the course specifically on autostereoscopic displays, which do not require glasses. Douglas and Matthew have done important research into this area – most notably this SIGGRAPH Asia 2010 paper, and have taught versions of this course not only at SIGGRAPH 2010 (as mentioned), but also at SIGGRAPH Asia 2010. Gregg has 15 years experience as an entrepreneur, inventor and researcher and has authored multiple key publications and patents relating to autostereoscopic display design.

Advances in New Interfaces for Musical Expression

This course is presented by Michael Lyons (Professor, Ritsumeikan University) and Sidney Fels (Professor, University of British Columbia) who in 2001 organized the first workshop on New Interfaces for Musical Expression (NIME). This workshop, dedicated to scientific research on the development of new technologies for musical expression and artistic performance, has since blossomed into a full-fledged international conference. This course will summarize the content of the last several years of NIME, including both theory and practice, and presenting several case studies.

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So there are those people out there that punch other people’s punchlines. Someone’s three quarters of the way through telling a joke, and a listener says, “oh, right, this one ends ‘to get to the other side’”. You don’t want to be that guy, but that’s a little bit how I feel writing about FXAA, given that there’s a whole course at SIGGRAPH next month about these sorts of antialiasing techniques. I blame Morgan McGuire’s Twitter feed, as he (and 17 others) retweeted Timothy Lottes’ posting that he had released shader code for FXAA. I’d seen FXAA mentioned before, NVIDIA put it in their DirectX 11 SDK. Which, frankly, is sadly misleading – the implication is that it works only on GTX 200-level hardware and above, when in fact it works on DirectX 9 shader model 3.0 hardware, GLSL 1.20, XBox 360, and Playstation 3, to name a few, and is optimized in various ways for newer GPUs. Anyway, seeing this shader code available, I was interested to try it out. Morgan mentioning that he liked it a lot got me a lot more interested. A few hours later…

So what the heck am I blathering about? To start, there are a number of these ??AA methods that are based on post-processing a color (and sometimes, also normal and depth) buffer. MLAA, morphological antialiasing, was the first used for 3D images, back in 2009. The basic idea is “find edges and smooth them”. The devil’s in the details, which is what the SIGGRAPH course will delve into (and I’ll certainly attend): how wide an area do you search to try to find a straight edge? how do you deal with curves and corners? how do you avoid oversmoothing thin edges, blurring them twice? how does it look frame to frame? and, most important if you want to use it interactively, how do you do this efficiently?

I’ve wanted an MLAA-like solution for two years, since before HPG 2009 when I noticed the MLAA paper on Ke-Sen’s pages and talked to Alexander Reshetov about it (who was very helpful and forthcoming). I even got a junior programmer to attempt to implement it in a shader, but the implementation was quite slow (due to a very wide search area) and ultimately flawed, and we didn’t have time to get back to it. Last year at SIGGRAPH there was a talk by a group in France, led by Venceslas Biri and Adrien Herubel, about implementing MLAA on the GPU, and they released source code. I spent a bit of time with their code, but it was developed on Linux and I had some problems getting it to work on Windows properly. My “I’ll just take a few hours and see where I get” time was gone, and still no easy solution. There were some other interesting bits out there, like the article in GPU Pro 2, Practical Morphological Anti-Aliasing, with even a github project, but there were different versions for DX9 and 10 (and not OpenGL), lots of files involved, and I didn’t want to get involved. Even Humus had a code sample, but I was still a bit shy to committing more time. (Also, his needs geometric information, and I wanted to antialias NPR edges formed by dilation, i.e., image processing, which have no underlying geometry).

Then the FXAA shader code was released: well-commented, with clear integration instructions, just needs a color buffer, and all in one shader file. FXAA is not the solution to all of life’s problems (or is it?), but for me, it’s wonderful. It took me all of an hour to fold into our system as a shader (and then another three debugging why the heck it wasn’t registering properly – our shader system turns out to be very particular about path names). The code runs on just about everything and has extensive comments. There are control knobs for the fiddlers out there, but I haven’t messed with these – it looks great out of the box to me.

So, after all that breathless buildup, here’s the punchline:

On the left is your typical jaggy image, on the right is FXAA. Sure, it’s not perfect – nearly-vertical lines can look considerably better with a wider edge search area (as seen in MLAA), dropouts could be picked up by supersampling or MSAA, thin lines can have problems – but this shader gives a huge improvement with no extra samples, and just one pretty-quick pass (plus – full disclosure – a preprocess of computing the luminance/luma (grayscale) and shoving it in the alpha channel). Less than 1 millisecond cost per frame on a GTX 480? Works on sRGB and linear? Code’s in the public domain? Sign me up!

See lots more examples on Timoty Lottes’ page. Read his whitepaper for algorithm details and his newer posts for tweaks and improvements. An easy-to-use demo of an earlier version of his shader can be downloaded here - just hit the space bar to toggle FXAA on and off. Enjoy!

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