Pixar is a lot more than a money-making box office powerhouse. It’s an innovative artistic studio that’s coming up with very cool solutions to new problems. One of those problems is figuring out how to realistically render certain things using a computer. One of the most difficult things has been the rendering of hair. From fur to human hair, it’s not easy to render millions of fibers that each have their own look, feel, transparency, and characteristics.
The art class of tomorrow will likely include computers. Since Pixar’s RenderMan is one of the best rendering tools on the market today, it’s worth seeing how this next-generation software is shaping the art classroom of tomorrow. In short, it’s making it so all a creative-minded student would need to do is come up with an idea, point, click, and render. Pretty crazy.
While it’s unlikely that all art classrooms will soon have access to a multi-million dollar rendering farm along with best-in-class software…it can’t hurt to see what’s happening on the bleeding edge of digital art these days. Here are a few creative new tools that Pixar has dreamed up to solve both old and new problems (and also tools that you might someday see in your school’s art classroom):
Note: these are tools from the Pixar Online Library and the descriptions may be a bit technical for those of us who are less art-inclined. Even so, it’s great to see how Pixar is tackling problems that never even dawned on me until now. Know of another cool artistic tool that would be in the art classroom of tomorrow? Let me know by tweeting @edudemic or responding in the comments. Thanks!
Drawing Hair / Fur
Hair is hard. Well, drawing hair is hard. If hair were actually hard, it’d probably be much easier to render. Since that’s not the case, the brilliant minds at work at Pixar have been coming up with innovative solutions to rendering hair on the big (and small) screen.
Their rendering software, RenderMan, works with the Autodesk program Maya that lets artists digitally add hair by basically pointing and clicking.
How does it work? Here’s the geeky technical description if you’re interested: RenderMan has a feature called Sigma Hiding, which may sound mysterious, but essentially it is an option that can be enabled to render small sub-pixel geometry, like fur, using smart techniques that Pixar has developed during its own productions. With Sigma Hiding images can be rendered more efficiently and have fewer artifacts, a direct example of a production driven feature.
Deep Shadows are special type of shadow map that can capture translucency, motion blur, and also be filtered to create smooth shadows. When used with fur and hair, Deep Shadows can create highly realistic results for a low cost (compared to ray tracing shadows on fur).
In Pixar’s feature animation, WALL•E, a key challenge was creating hundreds of shots for a world covered in debris. The trick was to add visual complexity as easily as possible. One solution was a displacement shader that could generate small garbage. This one shader was used in many scenes and could generate many types of looks.
The Tools of Tomorrow
Per H. Christensen
This course note describes a fast point-based method for computing diffuse and glossy global illumination, area light illumination and soft shadows, HDRI environment map illumination, multiple diffuse reflection bounces, final gathering for photon mapping, ambient occlusion, reflection occlusion, and volume scattering. [more] Additional materials: [Slides.pdf]
Per H. Christensen
This technical memo describes a fast point-based method for computing diffuse global illumination (color bleeding). The computation is 4-10 times faster than ray tracing, uses less memory, has no noise, and its run-time does not increase due to displacement-mapped surfaces, complex shaders, or many complex light sources. [more] Additional materials: [SlidesFromAnnecy09.pdf]
Oscillatory motion is ubiquitous in computer graphics, yet existing animation techniques are ill-suited to its authoring. We introduce a new type of spline for this purpose, known as a “Wiggly Spline.” The spline generalizes traditional piecewise cubics when its resonance and damping are set to zero. [more]
Detailed descriptions of the ray-tracing and photon-mapping algorithms for rendering complex scenes with indirect illumination, caustics, participating media, and subsurface scattering. The emphasis is on the practical insight necessary to use and implement these algorithms in production of high-quality image in movies, games, architecture, etc.
The passion for cooking and food are the central theme of Pixar’s recent film – Ratatouille. This complex and multi-faceted problem posed many challenges that were solved using diverse computer graphics and production techniques. In this course we will comprehensively cover all aspects including modeling, dressing, shading, lighting and effects.
An illustration of Gusteau comes to life and introduces a new facet of the film Ratatouille. To do this, a technique was needed to convert an animated 3D character into a 2D illustration. Existing renderman shaders based on normal and depth maps were difficult to control. [more]
In Pixar’s Ratatouille, a key story point involves a rat being swept through the sewers of Paris, plummeting down waterfalls and along steeply sloping tunnels, through a series of high-speed S- bends which cause the torrent of water to bank up sharply on each turn. [more]
This paper describes how we extended Pixar’s RenderMan renderer with ray tracing abilities. In order to ray trace highly complex scenes we use multiresolution geometry and texture caches, and use ray differentials to determine the appropriate resolution. With this method we are able to efficiently ray trace scenes with much more geometry. [more]
We present a new method for the efficient simulation of large bodies of water, especially effective when three-dimensional surface effects are important. Similar to a traditional two-dimensional height field approach, most of the water volume is represented by tall cells which are assumed to have linear pressure profiles. [more] Additional materials: [movie.avi]
We present a system for animating an articulate figure using a physical skeleton, or armature, connected to a workstation. The skeleton is covered with sensors that monitor the orientations of the joints and send this information to the computer via custom-built hardware. [more]
We present a solution to the aliasing problem for shadow algorithms that use depth maps. The solution is based on a new filtering technique called percentage closer filtering. In addition to antialiasing, the improved algorithm provides soft shadow boundaries that resemble penumbrae. [more]
A new reflectance model for rendering computer sythesized images is presented. The model accounts for the relative brightness of different materials and light sources in the same scene. It describes the directional distribution of the reflected light and a color shift that occurs. [more]
We propose a numerical method for modeling highly deformable nonlinear incompressible solids that conserves the volume locally near each node in a finite element mesh. Our method works with arbitrary constitutive models, is applicable to both passive and active materials (e.g. muscles), and works with simple tetrahedra without the need for multiple quadrature points. [more]
Local image histograms contain a great deal of information useful for applications in computer graphics, computer vision and computational photography. Making use of that information has been challenging because of the expense of computing histogram properties over large neighborhoods. Efficient algorithms exist for some specific computations like the bilateral filter, but not others. [more]