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RenderMan for Maya

Nov 1, 2005 12:00 PM, By John Monos

Alias Maya Gains Top-end Rendering Plug-in

In the late 80s, the RenderMan standard was born, describing a series of rules and specifications for creating a 3D scene. Through the RenderMan Interface Specification, a renderer is self-sufficient from modeling or animation software; just give the required inputs (camera, geometry, light sources, and shaders), and let the renderer worry about creating the image. Once it faithfully lives up to the specification, a renderer is dubbed “RenderMan-compliant.” The first and most evolved of such renderers is Pixar's implementation, PhotoRealistic RenderMan (PRMan).

This simple distinction of a renderer from a modeling or animation package gives rise to great flexibility in rendering and image control. It's also the reason so much technical overhead is necessary to get a RenderMan-compliant renderer configured for production. RenderMan for Maya aims to bring the flexibility of this paradigm into the hands of a Maya artist.

There are good reasons why PRMan has long been the renderer of choice among large effects houses and animation companies. Scalability, or the ability of handling complex scenes, is among the most important attributes of the renderer. PRMan has endured the abuse of film after film attempting to break it. This durability, coupled with the ingenuity of the REYES (Render Everything You Ever Saw) algorithm, which deals best with parametric surfaces (subdivision, NURBS, and patches), is what users depend on. Reliable texturing, motion blur, depth-of-field, and image filtering round out the core feature set of PRMan.

Programmable shading gives the ability to define the “look” of a scene by allowing one to carefully define surface characteristics, light interaction, and texture of an object. A programming language called RenderMan Shading Language handles this. There have been many tools that aim to take the inherently difficult task of shader creation and put it into the hands of the artist. Alias Maya artists use a Graphical User Interface (GUI) called Hypershade to create original shaders and material layering.

Most artists of off-the-shelf 3D packages take the integration of the renderer with the rest of the package for granted. Adding a third-party renderer to the mix in an intuitive way, is a job of shoe-horning the features of one into the other.

Enter RenderMan for Maya. This past August, I had the chance to visit with the folks at Pixar for a hands-on demonstration of RenderMan for Maya. Having used that standalone version of the renderer for many years, it was exciting to see an implementation of the renderer nested into Maya. Pixar has taken PRMan and combined it with Maya in a way where an artist can use his existing skill set and gain the benefits of RenderMan. Unlike other integration solutions, including Pixar's RenderMan Artist Tools, RenderMan for Maya does not sit atop of Maya, or run in parallel with the application: It's a plug-in that is loaded directly within the package, renders into the existing Render View/framebuffer, and leverages the existing interface.

Pixar's integration with Maya is well thought out. Much of the work necessary to get the scene to RenderMan is carefully managed behind the scenes. Multiple render passes are also handled intuitively with a mechanism for specifying dependencies. The basic Maya shaders have corresponding RenderMan versions, and for creating novel shaders, RenderMan for Maya translates Maya shading networks at render time. As with most software integration tasks, there is not necessarily a one-to-one correlation of features. Decisions must be made to as to how to give accessibility to the features in a workflow that is familiar to the users of the product. Pixar developers used existing Maya attributes, or, when this was not possible, added tabs and menus to existing interfaces.

In addition to integration tasks, many advanced features, such as Image Based Illumination, ambient occlusion, and subsurface scattering, have been pre-packaged. In previous RenderMan distributions, only the nuts and bolts are provided for these features, because users are expected to create their own implementations. RenderMan for Maya features a special case light shader, which drives global illumination techniques. Also included is a subsurface scattering method, which makes use of brick maps, PRMan's 3D point cloud format.

How does RenderMan for Maya differ from RenderMan Pro Server, the product the large studios are using? The core renderer is the same, though there are some features that aren't available in RenderMan for Maya. There is no command-line version of the shader compiler; you'll be limited with what you can dream up using Maya's shading utilities. There is also no support for DSOs (dynamically shared objects): These are plug-ins, which can extend the capabilities of the renderer. The limitations are not deal-breakers, because most people using the RenderMan for Maya product would not likely venture deep into the coding world.

The addition of RenderMan for Maya to the renderers already included with the distribution of the Maya invites comparisons. While comparing any two renderers is a difficult task, artists accustomed to the native Maya renderer will be impressed by the workhorse performance, speed, and scalability of PRMan. There will be some learning involved as the intricacies of the renderer are significantly different than Maya's.

Aimed at smaller shops, RenderMan for Maya is an approachable solution for those looking to expand their rendering capabilities. The software will be available in the third quarter of 2005 at a price of $995 via the Internet. While not the first product to attempt to integrate RenderMan into Maya, it's the most embedded solution to date. Film effects and animation have depended on the engineering found in PRMan for decades; RenderMan for Maya makes the same technology accessible for boutiques and individual artists.

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John Monos is a CG supervisor at Sony Pictures Imageworks, which is currently in production on Superman Returns.

© 2008 Penton Media, Inc.