After seeing Johnny Chung Lee’s wildly popular Wii head tracking video we were highly motivated to add this technology to our iRT ray tracer so colleague Joaquin Madruga quickly coded this function and we hit the road for GDC 2008.

Left to Right, Joaquin Madruga (IBM), Johnny Chung Lee (CM), Barry Minor (IBM) 

At the show we demonstrated two infrared (IR) LED tracked displays. The first was a target scene, similar to Johnny’s, that we created in 3dsMax and the second was a 7 million triangle China town scene created in Maya by our partners at Threshold Studios (Thanks Threshold!!). The target scene was easily ray traced on a single Linux Playstation3 but the China town scene required some real horsepower so we deployed six QS21 Cell blades and rendered it remotely using a GigE connected blade center.

Head tracking produces a very unique virtual window effect where the monitor appears to be a portal into a virtual world. The user wears a pair of IR LED equipped safety glasses which are tracked using an IR camera attached to the Playstation3. As the user moves, the view relative to the screen is computed and ray traced in real-time producing a strong motion parallax 3D effect. The next step for this technology will be passive head tracking using face tracking technology like that demonstrated by Richard Marks in the Sony booth at GDC 2008. What we need now is a passively head tracked 150” plasma with ray traced visuals at 120 frames/sec!!

iRT Head Tracking Video (YouTube)

iRT Head Tracking Video (Quicktime 28MB) 

The Boeing 777 was the first airliner to be 100 percent digitally designed using 3D computer graphics. The resulting digital mockup is 23,000x more complex than today’s typical digital game assets and therefore requires some serious muscle to render at interactive frame rates. Every subsystem including wiring harnesses, hydraulics, air-conditioning, and fuel delivery are modeled in excruciating detail. Prior research has shown that this is truly a supercomputer class problem which is why we have unleashed a prototype piece of LANL’s Roadrunner system on it at this years SC07 conference.

In the IBM booth at SC07 the 350M triangle Boeing digital mockup will be rendered real-time at 1080p resolution using a hybrid cluster of Cell processor based QS21 blades and a Ridgeback (AMD Opteron) memory server. The Ridgeback holds the 25GB digital model in its memory and services blade data request via NFS RDMA over 2GB/sec InfiniBand.  Each blade is responsible for a dynamic region of the screen and therefore only requires a fraction of the digital model to be cached in its local 2GB memory. These regions are further subdivided among the local SPEs which DMA via software caches from the address space of the Opteron forming a memory hierarchy that's transparent to the programmer.

                          128GB                   2GB                      256KB

(x86 disk) –> (x86 memory) –> (Cell memory) –> (SPE local store) –> (SPE register file)

          120MB/sec            2GB/sec              25GB/sec                 50GB/sec

IBM’s software ray-traced solution (iRT) has several key advantages:

1) Completely scalable renderer (Frame rate scales linearly with number of blades)

2) Much higher image quality using ambient occlusion

3) Ability to scale to very larger scenes while maintaining interactive frame rates

4) High compute density (no power hungry GPUs in the server racks)

 Sample frames: 

Many thanks to The Boeing Company and David Kasik for providing us with the 777 digital model. 

I recently ran across an interesting paper, Stackless KD-Tree Traversal for High Performance GPU Ray Tracing, which documented the strides made by GPU based ray-tracing over the last decade and introduced a new way of mapping acceleration structure traversal to modern GPUs, namely Nvidia's new G80. The paper was authored by Philipp Slusallek's talented computer graphics group at Saarland University in Germany. Our own Cell iRT ray-tracer was based on papers written by Philipp's students so we have great respect for their work. It was interesting to see the great lengths researchers are willing to go through in order to harvest a fraction of the floating point potential locked away in these black boxes.   

From 10,000 feet here's how the Cell processor stacks up to Nvidia's new G80 GPU:

Both parts are compared at 90-nanometre.  

As you can see the G80 is twice as big, which is a good indication it requires twice the power, and produces twice the floating point power on paper.  However when we ran one of the benchmarks discussed in the paper, the Stanford Bunny, we found that the Cell processor when combined with the iRT produces significantly better performance (we don't have access to the other datasets listed in the paper):

Left to Right:  

2.6 GHz AMD Opteron - Saarland Ray-tracer

Nvidia GeForce 8800 GTX - Saarland Ray-tracer

Sony Playstation3 (partial 3.2 GHz Cell processor running Linux) - IBM iRT

3.2 GHz Cell Processor - IBM iRT

IBM QS20 Blade (Two 3.2 GHz Cell Processors) - IBM iRT  

In fact one Cell processor is four to five times faster at ray-tracing the Stanford Bunny than the G80 and the Cell QS20 blade, which has comparable floating point power on paper, is eight to eleven times faster.  Both the G80 and Cell crush the AMD Opteron at ray-tracing which is arguably the most popular production rendering processor today. It's also interesting to note that secondary rays are less costly on Cell which is where ray-tracing becomes interesting.  Primary ray cast is only interesting from an academic perspective. The real issue is secondary rays and GPUs have traditionally had problems with these do to their incoherent nature. When you factor power into the equation it gets even more interesting, given that Cell is half the size of the G80 and produces five times the ray-tracing performance.  

Things are starting to get interesting and Intel is hot on the trail with their Larrabee part which is said to be designed for ray-tracing.  

Only time will tell….

We have now released a standalone version of the iRT for the Cell processor.  The downloadable Linux binary runs on both the Sony Playstation3 (PS3) and the IBM QS20 blade.

http://www.alphaworks.ibm.com/tech/irt

This demonstration program shows both the ray-tracing potential of the Cell processor and the scalability of code written using the Cell SDK.  Under Linux, the PS3 only has access to 6 of Cells 8 SPEs and has no access to the RSX graphics processing unit. Despite this the iRT can software ray-trace a 333,000 triangle car at interactive frame rates and can spin the 69,000 triangle Stanford bunny around in 720p at better than 40 frames per second. The iRT is also highly scalable, the IBM QS20 blade runs 2.5 time faster than the Linux PS3 and performance continues to scale linearly as additional QS20 blades are added.
 
On the alphaWorks site you will find the demonstration program plus two data sets, have fun!

The open side of the PS3 is a good way to get access to Cell technology as a programmer. Just head down to Toys-R-Us and toss 200 gigaflops into your cart. Programs like Stanford’s PS3 version of Folding@home are showing that today’s game consoles can form very potent compute clusters. In the video below (sorry about serpent like sound track) we show our IBM developed iRT ray-tracer running on a small PS3 cluster. This car model is 75x more complex than those used in today's games and ray-tracing is a class of rendering algorithm only deployed by the film industry, yet PS3s when clustered together handle this problem with ease. Our code was written using the Cell SDK so the same binary that was developed for the QS20 blade runs fine on the PS3, no changes. We just grabbed our Yellow Dog DVD, installed Linux on the PS3s, copied over the iRT binaries, and in minutes we had a very low cost 600 gigaflop cluster. While it's no match for LANL's massive Roadrunner system the same code can be run on both clusters.

A source at Sony’s invitation-only PlayStation3 media day (now underway at a gallery in SoHo) phones in with an update:

• 15 titles are being previewed, from both Sony and 3rd-party developers
• The titles are being shown on 42″ HD plasma screens, at 1080p
• Some of the most striking titles include Resistance: Fall of Man, NHL 2K7, NBA 2K7, and Lair
• Great media buzz at the event
• When asked how the titles looked on the HD screen, my source simply said (speaking of the NBA game) “I swear, it looks like live television.”

Sounds like a tough assignment!

Technorati tags: PlayStation 3, Sony

Via PS3land.com…

“According to an IGN report, Sony has signed a partnership with the Folding@home distributed computing project which will allow the development of a client to “allow idle Cell Processors to turn their considerable computational power from crunching the polygons that makeup curvaceous videogame breasts to crunching the math of folding proteins hold the secret to curing cancer”. And instead of purchasing surper-computers which run on the Cell, Folding@home will be using 10,000 PlayStation 3s.

According to the IGN article, “The Cell Processor is expected to perform calculations for Folding@home on the scale of 100 gigaflops”, which translates to a quadrillion floating point operations a second- “enough so that project leaders are now considering expanding their simulations to study Alzheimer’s and Huntington’s Diseases and other forms of cancer.”

Tags: PS3 , PlayStation , Cancer , Sony , Cell