Carmack excited about Nvidia's Project Denver, continues ray tracing research

Nvidia's recently announced move into CPU territory with Project Denver has been very well received by the general public. Game developers (who have known about this project for over a year) like John Carmack have also expressed interest. Most people are tired of the current x86 duopoly held by AMD and Intel, and for them this archaic 30+ years old legacy technology cannot die fast enough. Carmack is especially happy about Nvidia's choice for ARM because he is already familiar with coding for the ARM CPUs in mobile devices like Apple's iPhone and Google's Android.

From his twitter acount:

"I have quite a bit of confidence that Nvidia will be able to make a good ARM core. Probably fun for their engineers."

"Goal for today: parallel implementation of my TraceWorld Kd tree builder"

"10mtri model got 2.5x faster on 1 thread, 19x faster on 24 (hyper)threads."

"Amdahl’s law is biting pretty hard at the start, with only being able to fan out one additional thread per node processed."

As can be seen from his twitter entries, he also restarted his research on ray tracing. One specific thing to note is that he's talking about Amdahl's law. I first saw this law in a Siggraph 2008 presentation by Jon Olick on parallelism, and it is something that will be hampering traditional rasterization more than raycasting/raytracing. From wikipedia (Amdahl's law):

"The speedup of a program using multiple processors in parallel computing is limited by the time needed for the sequential fraction of the program. For example, if 95% of the program can be parallelized, then the theoretical maximum speedup using parallel computing would be 20 times faster, no matter how many processors are used. "

And a few thoughts related to Amdahl's law from Carmack's talk at QuakeCon 2010 in August (see http://raytracey.blogspot.com/2010/08/is-carmack-working-on-ray-tracing-based.html), implying that current GPUs, no matter how powerful, can only speed up the code to a certain extent and that scalability on multi-core CPUs is better (because contrary to the GPU, multi-core CPUs can speed up the serial code parts as well):

"so I’m going through a couple of stages of optimizing our internal raytracer, (TreeWorld used for precomputing the lightmaps and megatextures, not for real-time purposes) this is making things faster and the interesting thing about the processing was, what we found was, it’s still a fair estimate that the GPUs are going to be five times faster at some task than the CPUs. But now everybody has 8 core systems and we’re finding that a lot of the stuff running software on this system turned out to be faster than running the GPU version on the same system. And that winds up being because we get killed by Amdahl’s law there where you’re throwing the very latest and greatest GPU and your kernel amount (?) goes ten times faster. The scalability there is still incredibly great, but all of this other stuff that you’re dealing with of virtualizing of textures and managing all of that did not get that much faster. So we found that the 8 core systems were great and now we’re looking at 24 thread systems where you’ve got dual thread six core dual socket systems. It’s an incredible amount of computing power and that comes around another important topic where PC scalability is really back now "

Nvidia's project Denver is very important in this respect and will bring the theoretical maximum speedup (limited by Amdahl's law) much closer to reality, because CPU cores and GPU cores are located on the same chip and are not depending on any bandwidth restrictions. The ARM CPU cores will take care of the latency sensitive sequential parts of the code, while the CUDA cores will happily blast through the parallel code. For ray tracing in particular, this means that the ARM CPU cores will be able to dynamically build acceleration structures and speed up tree traversal for highly irregular workloads with random access, and that the plentiful CUDA cores will do ray-triangle intersection and BRDF shading at amazing speeds. This will make the Denver chip a fully programmable ray tracing platform which greatly accelerates all stages of the ray tracing pipeline. In short, a wet dream for ray tracing enthusiasts like myself :D! Based on the power-efficient ARM architecture, I think that Denver-derived chips will also be the platform of choice for cloud gaming services, for which heat and power inefficiency from the currently used x86 CPUs are creating a huge problem.

Watermelon

Working on lighting and texturing this scene of a watermelon on a picnic table...everything in the image is CG, the background is actually a photoshopped picture of a forest...

I have to finish the slice of watermelon, the plate, and the table cloth...

Please feel free to critique my texture...but please keep in mind I wasn't allowed to hand paint or use photo reference for the textures, this is all procedurally generated by maya...

Edit: Final render...calling it finished...

Arnold render to have full GPU acceleration in a few years

I've come across this very interesting interview about Arnold render, Sony Image Works' primary production renderer for CG feature films: http://www.3dworldmag.com/2011/01/07/pros-and-cons-of-gpu-accelerated-rendering/

Some excerpts from the interview:

"The first target for that backend is the CPU, and that’s what we’re using now in production. But the design goals of OSL include having a GPU backend, and if you were to browse on the discussion lists for OSL right now, you would see people working on GPU-accelerated renderers. So that could happen in future: that a component of the rendering could happen on the GPU, even for something like Arnold."

"it doesn’t make sense to cram the kinds of scenes we throw at Arnold every day, with tens of thousands of piece of geometry and millions of textures, at the GPU. Not today. Maybe in a few years it will."

Arnold render is a unidirectional path tracer, so it makes a perfect fit for acceleration by GPUs. "Maybe in a few years it will" could be a reference to Project Denver. When Project Denver materializes in future high-end GPUs from Nvidia, there will be a massive speed-up for production renderers like Arnold and other biased and unbiased renderers. The implications for rendering companies will be huge: all renderers will become greatly accelerated and there will no longer be a CPU rendering camp and a GPU rendering camp. Everyone will want to run their renderer on this super-Denver-chip. GPU renderers like Octane, V-Ray RT GPU and iray will have a headstart on this new platform. Real-time rendering (e.g. CryEngine 4) and offline rendering (e.g. Arnold) will converge much faster since they will be using the same hardware.

AMD and Intel will not sit still and recently launched Fusion and Sandy Bridge, which basically follow the same philosophy as project Denver, but coming from the other side: while Nvidia is adding CPU cores to the GPU, AMD and Intel are adding GPU cores to the CPU. Which approach is better remains to be seen, but I think that Nvidia will have the better performing product as usual. Eventually there will no longer be a distinction between CPUs and GPUs, since they will all be merged on the same chip: a few latency-optimized cores (today's CPU cores) which process the parts of the code that are inherently serial and are impossible to parallellize and thousands of throughput-optimized cores (today's GPU cores or stream processors), which handle the parallel parts of the code, all on the same chip using the same shared memory pool.

The coming years will be very exciting for offline and real-time graphics, in particular for raytracing based rendering. Photon mapping for example is a perfect candidate that could become real-time in a couple of years.