Issue: Volume 36 Issue 5: (July/August 2013)

Graphic Cards Grow Up


Gavin Greenwalt

The Return of PowerVR

PowerVR is not a name that has come up often in CG circles in recent years; the last time 3D artists were considering the merits of a PowerVR product it was probably in a shootout with a 3dfx Voodoo or Nvidia GeForce 256 at the "turn of the century." For those who have forgotten the GPU wars of the '90s, Imagination Technologies' PowerVR chips were known for their efficiency and economy; however, when pitted against Nvidia's or 3dfx's offerings, inevitably came up short in raw power.

Not finding a solid market with frame-rate-obsessed PC gamers, Imagination refocused its efforts on the emerging mobile and integrated graphics markets, where its efficiency and economy were key metrics, eventually even providing the GPU that powers both the Apple iPhone/iPad and Samsung Galaxy line of phones. As a result, Imagination Technologies and its PowerVR brand have mostly disappeared from the attention of the average 3D artist who relies on power-hungry, cutting-edge technology.

However, following a number of acquisitions and a newfound interest in raytracing, Imagination Technologies hopes to make its new Caustic Professional group and PowerVR brand household names in the CG industry once again by making raytracing interactive and fast.

If the name "Caustic Professional" sounds vaguely familiar, it's because it very well could be to many. Caustic Graphics was a start-up founded several years ago by several ex-Apple engineers who had come up with a novel solution for how to efficiently accelerate raytracing and overcome the limitations imposed by traditional GPU renderers. They developed a prototype card and a low level raytracing API, but had no software to prove its potential. This would be like ATI having a GPU but no games to run on it.

To fulfill this omission, Caustic acquired Splutterfish, developers of the Brazil R/S production renderer used on numerous feature films, from Star Wars to Avatar, to port its rendering technology to what is now PowerVR OpenRL, Caustic's raytracing API.

Caustic's combined hardware and software capabilities caught the eye of Imagination Technologies several years ago, and Imagination acquired Caustic Graphics (now called Caustic Professional), integrating Caustic's technology into its product line and road map. The newly released Caustic Series2 hardware and Visualizer Plugins are the fruition of this partnership between Imagination's experience in hardware development, Caustic's innovative raytracing chip design, and the Brazil team's production-proven photorealistic Brazil raytracer.

A Competing Standard is Born

By this point in time I'm sure you're familiar with OpenGL, CUDA, and OpenCL. CUDA being Nvidia's proprietary GPGPU standard, and OpenCL being the Khronos group's open alternative. Well, as is the nature of this industry, you're going to keep track of one more: PowerVR OpenRL. As with CUDA and OpenCL, any renderer that has OpenRL support will run on OpenRL hardware. OpenRL, unlike CUDA and OpenCL, however, is not a general-purpose API - you aren't going to be accelerating H264 compression or running PhysX physics simulations.

Imagination and Caustic are calling their chip an RTU, which stands for "Ray Tracing Unit" to distinguish it from a GPU. What this means for artists is that just like iRay will only be accelerated by Nvidia's CUDA GPUs, OpenRL applications will only be accelerated by OpenRL-supported RTUs (or default to an optimized CPU-only implementation). And conversely, until V-RayRT or iRay add support for OpenRL as they have for CUDA, neither will be hardware-accelerated by the only chips that currently accelerates PowerVR OpenRL: Caustic's Series 2 raytracing cards.

At this point I can hear your inevitable question through the ether of the Internet. "So what you're describing is a new standard, purpose-built hardware that promises improved performance - created by a start-up that is acquired by a large international GPU design company…isn't this just Ageia's PhysX all over again?" This is a fair question and I think probably the concern that will be one of the largest hurdles to the success of Caustic in the near term.

As an artist, I would argue that the similarities are superficial. Most importantly, the two products are competing in very different markets. PhysX was targeted at gamers who ultimately are hobbyists and, therefore, don't "need" a physics accelerator. Physics are also somewhat tangential to the gaming experience. They enrich the gaming experience, but they don't define it. Contrast that to a professional artist who both financially benefits from better performance and the ubiquity of raytracing in a 3D artist's work, and the cost/benefit ratio is quite different. If, hypothetically, Ageia had accelerated FumeFX or RealFlow, for instance, instead of Crysis, I think history may have played out very differently.

The last thing I would contrast is that while Nvidia acquired and discontinued Ageia's physics hardware division to protect its GPGPU efforts, Imagination Technologies appears to be embracing OpenRL and has committed substantial resources to developing the Caustic 2 RTUs and integrating PowerVR OpenRL acceleration into its product road map. Imagination tells me it intends to integrate OpenRL into tits entire lineup - bringing real-time raytracing to every platform, from the professional workstation to smartphones.

On top of the low-level OpenRL standard, Caustic has also developed the PowerVR Brazil SDK. The Brazil SDK in relation to OpenRL can be thought of much like the Unreal Engine to OpenGL or Direct3D. It takes the low-level OpenRL raytracing API and creates a more developer-friendly and feature-complete platform. The Brazil SDK is a from-the-ground-up rewrite of the Brazil R/S production renderer but built this time with interactivity and hardware acceleration in mind. It's on top of this higher level rendering tool kit that Robert McNeel and Associate's Neon raytracer for Rhino 5.0 is based, as are Caustic's own Visualizer plug-ins.

Gavin Greenwalt is a VFX supervisor and senior artist for Straightface Studios in Seattle. He can be reached at Gavin@SFStudios.com.

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