GPU Ray tracing

Award-winning PowerVR GR6500 ray tracing GPU tapes out

Last month I sent out a message on Twitter announcing that the latest PowerVR Wizard ray tracing GPU test silicon had taped out, based on Imagination’s reference design and the IC Compiler™ II place and route solution from Synopsys.

Given the enthusiastic response from developers, I thought I should write a short article about how we got here.


Firstly, I’d also like to take this opportunity to congratulate everyone in the engineering team; they have worked really hard to take the Wizard architecture from a theoretical concept to a mature, real-world implementation that can now be found in silicon.

For those who haven’t kept track of our ray tracing solution, the PowerVR GR6500 GPU is the culmination of eight years of effort from a global team of designers. The technology was originally conceived at Caustic Graphics, a startup with a vision for interactive ray tracing, going against twenty years of industry momentum.

I recently had a chat with Luke Peterson, Imagination’s director of research for PowerVR Ray Tracing, who revealed some details about the team’s beginnings in the semiconductor industry.


We approached the problem differently. While others in the industry were focused on solving ray tracing using GPU compute, we came up with a new approach leveraging on our prior expertise in rasterized graphics. This allowed us to challenge assumptions that the rest of the industry took for granted and cleared the way for some major breakthroughs.

Their incredible work was soon recognized by several high-profile peers working in graphics. Academy Award Honoree Matt Pharr, co-author of Physically Based Rendering, from Theory to Implementation, had this to say about our technology:

The [PowerVR] Wizard architecture offers the possibility of a quantum leap forward in image quality in mobile interactive graphics applications.

In addition, John Carmack, co-founder of id Software and current CTO of Oculus, declared the following about PowerVR Ray Tracing:


Overcoming the initial challenges

One of the first technical challenges the ray tracing team faced was that the memory bandwidth requirements were orders of magnitude higher than what available technologies of the time could offer. This prompted the engineers to cleverly invent an efficient scheduling and sorting algorithm to amortize data reads across many simultaneous queries into a spatial database.

A big business challenge came in 2009; during the global financial crisis, Caustic’s investors could no longer fund the company. The team however continued development, based on the strong belief in the potential of the technology that they were building.

Soon after, Imagination acquired Caustic and integrated the ray tracing group within the PowerVR Multimedia division, leading up to the launch of the PowerVR Wizard ray tracing architecture.

The road to tape out

One of the many advantages of PowerVR Wizard ray tracing GPUs lies in the power efficiency gains delivered by the architecture. Thanks to the innovative nature of the design, the majority of data can remain in a subset of the local cache, eliminating the need for any high bandwidth random access path between processing elements and internal cache memory.

This coherence gathering results in huge savings in memory bandwidth and power consumption, making Wizard ray tracing GPUs 100x more efficient compared to using GPU compute or other software-only ray tracing approaches on traditional graphics architectures. The approach has the added benefit of recollecting SIMD coherence, enabling graphics processors to tackle previously unapproachable challenges.

The success of the Wizard design team is based on a number of factors, including commitment to a long-term vision, ambition and tenacity.

Along the way, the PowerVR Ray Tracing team collected multiple nominations for high-profile awards; recent examples include Best Technology Innovation at The Inquirer 2015 Tech Hero Awards and Design Team of the Year at the 2015 UBM ACE Awards.

Having delivered the technology that will change the state of the art in mobile and embedded graphics, we can’t wait to put it in the hands of developers!

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