Imagination pushes ray tracing

Imagination pushes ray tracing

Technology News |
By Nick Flaherty

History has a way of repeating itself, especially in the electronics industry.

Back in the day, Imagination Technology came up with a smart way to reduce the computing power required for rendering 3D images using a two dimensional tile. However, this was very different from other 3D rendering approaches. The company struggled to persuade the industry that the 2D tile was a more effective approach. It did in the end, with IP deals with ARM and Apple for mobile phones and ST Microelectronics for desktops, but it was a long process educating the games industry.

The same thing is happening again with ray tracing. Instead of drawing lots of polygons, this technique traces the rays of light. This provides higher quality reflections to boost the image, but needs a lot more processing power and so is the domain of power hungry Graphics Processing Units (GPUs) from companies such as Nvidia and AMD.

Again, Imagination has come up with some core IP, with 200 patents dating back to 2014, that dramatically simplifies the processing required. This means the thousands of billions of operations (TFLOPS) from a GPU put Imagination at a disadvantage when it can achieve the same quality with a fraction of the processing power.

So this time, with ray tracing becoming increasingly important for a wide range of graphics applications including mobile, Imagination has developed a Ray Tracing Levels System.

This is to give developers and OEM an insight into the capability of solutions for ray tracing acceleration available now and in the future, it says.

“Real-time ray tracing is the most exciting development in 3D graphics of the last 10 years. It’s a technology that everyone wants but not everyone understands, especially when it comes to the benefits on mobile. We want to change that. By creating the Ray Tracing Levels System, we’re helping to bring clarity to the industry about the confusing range of different ray tracing offerings,” said Kristof Beets, Senior Director of Technical Product Management at Imagination.

How the architectures handle ray tracing matter, he says.

“GPUs love coherent processing, so with rays all travelling in the same direction, that’s great for processing. Divergent rays, that’s not good for GPUs, they traverse the memory in different ways and that gives inefficiencies in memory and execution,” he said.

“Just like with tile rendering, we introduced a new box that looks at all the rays and bundles coherent rays together to identify hidden coherency to group for processing and memory access, eg different reflections from same object. It’s the same as tile rendering, we are doing it in 3D now rather than 2D images.”

To highlight these differences, the Ray Tracing Levels System identifies increasingly advanced stages of ray tracing acceleration, across a range of architectures, not just Imagination’s PowerVR Ray Tracing, with each level providing higher performance and better hardware utilisation. This translates to greater real-world ray tracing performance with better efficiency for more complex effects and higher resolutions.

The system has six levels:

  • Level 0: Legacy solutions (used in architecture and graphics workstations)
  • Level 1: Software on traditional GPUs
  • Level 2: Ray/box and ray/tri-testers in hardware
  • Level 3: Bounding Volume Hierarchy (BVH) processing in hardware
  • Level 4: BVH processing and coherency sorting in hardware
  • Level 5: Coherent BVH processing with Scene Hierarchy Generation (SHG) in hardware

Analysist agree the hierarchy could help. “The Ray Tracing Levels System is exactly what is needed to understand and reap the benefits of ray tracing across a range of products,” said Jon Peddie, Principle, Jon Peddie Research. “Ray tracing has long been considered the utopia of 3D graphics, but the proliferation of solutions makes it far from clear whether people are even referring to the same

Beets points out that Imagination had a level 5 system back in 2015. “Everyone is focussed on tracing the rays in L4 and the BVH comes from CPU or GPU coming from shader programmes but with full ray tracing acceleration you could move that into hardware as well. In our Plato hardware in 2015 we had a dedicated hardware for more detailed and dynamic 3D schemes, particularly with an animated character,” he said,

However the other key lesson was the role of the application programming interface (API) for developers to use without having to worry about the underlying hardware. Imagination has been a key part of developing the DXR and Vulkan APIs

“DXR has been a key influence on Vulkan, and there the BVH is not specified, that’s up to the hardware,” he said. “The APIs give us an enormous amount of freedom for optimisation so the developer doesn’t need to worry about  it. Where they will see a difference is what they will achieve, the utilisation out of the performance budget.”

Imagination is of course developing designs for IP for ray tracing, set to launch later this year. This is aimed at the mobile gaming market where there this a chip power budget of 2W, but can also be scaled up to streaming servers in data centres. Here, the games run on the servers with the displays compressed and sent over a broadband link. Again, power consumption is vital to allow more servers to operate in a data centre rack. “We could upgrade those GPUs for higher image quality – cloud gaming is one of the target markets,” said Beets.

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