Since the ompf.org forum (the one and only forum for ray tracing aficionados) has been down for over a week, and only the administrator can bring it back online, Jacco Bikker has set up a server with a temporary replacement for the forum (see comments in the previous post) and asked me to point the readers of this blog who frequented ompf (and who are -like me- craving for a daily dose of ray tracing news with accompanying withdrawal symptoms) to the new address at:
The developers behind the Brigade path tracer (Jacco Bikker and Jeroen van Schijndel) have released two very impressive videos on Youtube and the jump in quality and performance is quite huge. The scene in the video runs smoothly on just one GTX 470 at 8spp and 640x360 render resolution (1280x720 display resolution) with very little noise:
This latest version of the Brigade path tracer contains at least two major improvements compared to previous versions: multiple importance sampling and a Blinn shader for glossy materials (e.g. the floor) which greatly enhances the realism of the scene (and seems to converge very fast). The kernel now runs on the GPU only.
Very impressive what they have achieved so far. With an extra GPU, the noise should almost vanish and become imperceptible after playing a while. And with Nvidia's Kepler and AMD's compute-focused GCN (HD7000) on the horizon, this path tracer is going to become very interesting (when the code will be ported to OpenCL in AMD's case). Something like real-time photorealistic chess rendered on the GPU is very close now. Jacco also mentions in the comments under the video that a new game is in the works with support for animated objects (including skeletal animation).
The mere thought of having truly real-time, photoreal global illumination in games is the most exciting thing that has happened in computer graphics over the past ten years. The last time I was this excited was with the introduction of real-time lighting and shadowing with normal mapping in Doom 3, first shown to the world on the MacWorld Expo 2001:
I can't wait to get my hands dirty and experiment with the new Brigade code.
A paper about the out-of-core GPU ray tracer CentiLeo, entitled "Out-of-core GPU ray tracing of complex scenes" is available at ACM here: http://dl.acm.org/citation.cfm?id=2037826.2037854(behind a paywall).
If you don't have an ACM subscription, you can still read a free version of the paper by downloading the file "Supplemental files" under the tab "Source Materials" on the same page.
The paper contains an interesting analysis of the overhead of the out-of-core GPU ray tracing algorithm compared to the in-core Aila/Laine GPU ray tracing algorithm.
Details about the scene and system used are in the video description (average rendertime 2.5 min at 720p HD resolution with only 1 GTX580).
Besides the fact that it looks so unbelievably real, the most interesting part about this animation is that it was rendered from within 3ds Max, using an in-development plug-in version of Octane Render that is completely integrated with the Max software. This will enable users to edit, move, add and delete geometry and lights in the scene and see the results instantly rendered in the viewport with Octane Render's photorealistic quality. It also eliminates the lengthy per-frame export times (in some cases longer than the actual rendertime of the frame itself) which will do wonders for animation rendering. I think this integration is going to become Octane's new killer feature which will take insanely fast photorealistic rendering on the GPU to the next level.
There is now a stable release of Exposure Render, the open source direct volume renderer with physically based lighting on the GPU: http://code.google.com/p/exposure-render/
It now even runs on a laptop with a 8600M GT (and all the example datasets fit in the GPU memory). The photoreal lighting makes this renderer stand out when compared to other volume renderers. And it converges surprisingly fast. Some pictures (rendered for only 20 seconds on the ultraslow 8600M GT):
Awesome news!!! In addition to the partnerships with Refractive Software (makers of Octane Render) and the development team behind the Brigade path tracer (which I blogged about here), OTOY now announced a partnership with Autodesk to integrate Octane Render into the viewport of Autodesk's 3D Studio Max 2012 and stream real-time path traced visuals for animations, movies and games from remote GPU clusters in the cloud to the client. Real-time GPU path tracing is big business, and the best part is that it's going to bring game graphics up to ultrarealistic levels in the not too distant future.
Some quotes from the article and official press release:
Real Time Path Tracing in the Viewport - A New Level of Photorealism
OTOY's 3D rendering tools, including Octane Render™ and Brigade™, are the premier rendering solutions for next generation 'path traced' games and films.
Path tracing significantly reduces the cost and complexity of high quality rendering by automatically generating effects traditionally handled through manual post processing – including spectral rainbows, lens flares, unbiased motion blur and depth of field.
“A year ago, path tracing was considered too expensive to be used even in high-end Hollywood blockbusters. Today, thanks to advances in GPU rendering, OTOY is bringing real time path-tracing technology to millions of artists by leveraging GPU hardware that costs only a few hundred dollars. This is a game-changer on any budget,” said Jules Urbach, CEO of OTOY.
“Autodesk is the leader in 3D design software for film and video game production. We are incredibly excited about our partnership and proud to be bringing their industry leading tools to an ever-expanding market through our cloud solutions,” said Alissa Grainger, President of OTOY.
Another test in my never relenting quest for real-time photorealistic graphics. This time I was inspired by one of the first animations rendered with unbiased Monte Carlo path tracing. The animation was made by Daniel Martinez Lara from Pepeland in 1999 and can be seen here:
It’s one of the first animations that uses Arnold, the Monte Carlo path tracing based production renderer developed by Marcos Fajardo, that is currently taking Hollywood VFX by storm: it was used in e.g. Cloudy with a Chance of Meatballs, 2012, Alice in Wonderland and the Assassin’s Creed: Brotherhood and Revelations CG trailers and is giving PRMan and mental ray a run for their money (probably making them obsolete soon, mainly because of ease of use and huge artist time savings). The animation shows a very lifelike clay figure coming to life. Despite the simplicity of the scene, the whole looks very believable thanks to physically accurate global illumination and materials and an extensive use of depth-of-field and camera shake.
In an attempt to reproduce that particular scene, I’ve used the animated Ogre model from a ray tracing demo developed by Javor Kalojanov which can be found at http://javor.tech.officelive.com/tmp.aspx. The Ogre model (which was created by William Vaughan) consists of 50,855 triangles and was also used in the excellent paper “Two-level grids for ray tracing on GPUs” by Javor Kalojanov and Philipp Slusallek (really great people btw, whom I've had the pleasure to meet in person recently. The conversations I've had with them inspired me to finally try triangles as primitive for my real-time path tracing experiments (instead of just spheres), which led to this Ogre demo. To my surprise, triangle meshes are not that much slower to intersect compared to spheres. I think this is due to the fact that the cost of primitive intersection is becoming increasingly smaller compared to the cost of shading).
The following videos show an animated Ogre path traced in real-time with real-time, per frame update of the acceleration structure of the Ogre’s 50k triangle mesh (watch in 480p):
Path tracing is performed entirely on the GPU, in this case a GTS 450 (a low-end GPU by today’s standards). The framerate of the walk animation is about 4 fps max on my card but should be around 15-20 fps on a GTX 580. The image converges extremely fast to a very high quality result (in about 1-2 seconds). The movement of the Ogre (translation, rotation, animation) is actually much more fluid in real life without Fraps, the overhead of the video capturing software almost halfs performance.
The images below were each rendered at 20 samples per pixel in under 2 seconds on a GTS 450 (it would take less then 0.5 seconds on a GTX 580):
Note the very subtle color bleeding from the ground plane onto the Ogre:
With a glossy floor:
If you’re interested in trying this scene out yourself, send me an e-mail at sam [dot] lapere [at] live [dot] be. A CUDA enabled GPU is required (minimum compute capability 1.1).
I’m planning to build a (very) simple game with this tech. The possibilities are really endless. We're on the cusp of having truly photorealistic games.
Another experiment: no spheres this time, but a real-time animated triangle mesh (the hand is from the Utah 3D Animation Repository, a textured mesh containing 15,855 triangles). The goal was to create a simple animated scene and achieve a look as close to photorealism as possible with completely dynamic, physically accurate global illumination in real-time using path tracing.
The following animation was rendered in real-time on a GTS 450 (stretching the compute capabilities of my GPU to the max):
The image below was rendered with path tracing at 26 samples per pixel in 0.8 seconds on a GeForce GTS 450 (192 cuda cores at factory clocks, it would render 3 to 4 times faster on a GTX 580, which has 512 cuda cores and is clocked higher):
Two new great looking videos of Exposure Render, the real-time CUDA-based volume path tracer have appeared on Youtube. It's quite cool to see these anatomical volume datasets being rendered with physically based shading in near real-time:
Wow, the developers behind Octane render never cease to amaze. After being the first GPU renderer to implement Population Monte Carlo (a more complex rendering method than plain path tracing which borrows concepts from Metropolis light transport and energy redistribution path tracing to handle scenes with difficult lighting more efficiently), Octane render is now adding unbiased subsurface scattering along with other features such as instancing. Here's the announcement post from radiance (Octane's main developer) over at the Octane forum:
"We have fully working and VERY fast SSS ready for release in the next test version. It renders about as fast (a tiny bit slower) as a glossy specular material. And, it's unbiased/bruteforce SSS, eg no bias introducing photon grids or other precomputed approximations. [...] This is the prime new feature in the next test release, along with instancing support and FAST voxelisation, and another suprise feature, aswell as the soon to be publically released first of a series of new products, OctaneRender for 3DS Max."
Surprise feature? Refractive Software knows how to keep their audience hyped ;-)
Some screenshots with the new SSS method can be seen in this thread.
I think it will eventually be possible to implement every feature found in traditional CPU renderers on the GPU and make it an order of magnitude faster. For example, Radiance hinted at bidirectional path tracing + PMC:
"Bidirectional pathtracing (and PMC) should make renders like this one converge MUCH faster and bidirectional pathtracing + PMC is something we will be starting work on next, after 2.5 is out. PMC + bidirectional will be ideal, it will be as efficient as the popular standard in CPU based unbiased engines (MLT+bidir), and this combined with the power of GPUs should really take things to a new level."
GPU rendering is going to redefine every area of rendering from movies, animation, visualization and design to games, simulation and virtual reality. Truly the most exciting time for rendering in decades. I'm very happy that this paradigm shift is in full swing and that things are evolving at nauseating speed :-)
The video shows an eerily realistic representation of a person scanned with CT (computed tomography), where anatomical layers of skin, muscle, cartilage, connective tissue and bone can be peeled away and rendered with photorealistic quality global illumination in real-time. This could be an extremely useful training tool for medical students and aspiring surgeons. The physically based photorealistic 3D renders of skull, bones and soft tissue could also benefit radiologists in diagnostic decision making.
Most medical volume rendering software uses ray casting, which is fast but provides very unrealistic looking lighting. With volumetric path tracing finally being feasible in real-time thanks to the GPU, this will hopefully change soon. I think we will see an implementation of real-time path traced sparse voxel octrees pop up sometime in the very near future.
Anyone interested in OpenGL and micropolygons should definitely check out the following 1-hour-long video presentation by Kayvon Fatahalian, "Evolving the OpenGL Graphics Pipeline in Pursuit of Real-Time, Film-Quality Rendering":
12 samples per pixel, max path length = 4, 584x266 render resolution, Stanford Bunny with 69k triangles (rendered in about 0.4 seconds on a low-end GTS450):
This will eventually become a full-fledged game inspired by this video:
A few days ago, an article appeared on the Japanese website 4gamer.net about an in-development PowerVR GPU, the PowerVR RTX, which is said to have integrated ray tracing hardware from Caustic Graphics (acquired by Imagination Technologies in December 2010). The article is in Japanese, and the Google translated version is barely understandable:
The following two videos of "Unbiased FPS" were rendered on a GTS 450 and demonstrate mouse look, shooting mechanics and how adjusting the number of averaged frames affects the amount of noise and blurring. Youtube has a terrible video compression algorithm for videos containing fine-grained noise (such as Monte Carlo noise), so these came out much worse than expected:
The frame averaging technique (implemented by Kerrash) significantly reduces the amount of noise without affecting the framerate, but the resulting blurring of fast moving objects is of course less than ideal. At the upcoming Siggraph Asia 2011, a paper entitled "Image-space bidirectional scene reprojection" will be presented which could potentially solve the blurring issue by reconstructing additional frames without distracting blurry artefacts (there are two versions, a raster based version and an image-based one). The video accompanying the paper shows a lot of promise and is definitely worth checking out: http://research.microsoft.com/en-us/um/people/hoppe/proj/bireproj/
On a sidenote, I found a new, short video of the Brigade path tracer, showing a real-time pathtraced animated character: http://www.youtube.com/watch?v=RbxoZK6Apj8 (no details on the hardware used)
The video shows very nice soft shadows and path traced ambient light coming from the skydome (calculated in real-time contrary to the constant ambient term which is used by many games to approximate indirect lighting).
Another small experiment to see how a path traced first person shooter game might look like (all screenshots rendered on a 8600M GT):
4spp, reusing samples from the previous 6 frames, 720p resolution:
720p resolution, 4spp with 12 averaged frames (reusing samples from the previous 12 frames, resulting in heavy blur for moving objects, but crisp image quality for the rest of the scene):
Some features:
- a first person "gun" sticks to the camera and shoots chrome balls with physical weight
- mouse look is semi-functional, you can move the mouse cursor up to the borders of the screen
- the car can be controlled with the arrow keys
- the robot has an initial angular momentum, but essentially does nothing
- the camera is controlled with mouse + WASD keys (the classic FPS controls)
- the number of averaged frames can now be set with a slider (from 0 to 12). It regulates the amount of "blur" caused by reusing samples from previous frames and is very useful for comparison purposes. Setting the slider to 1 or higher greatly reduces the amount of noise at the expense of a more blurry image and doesn't have any impact on the framerate. You can for example quadruple the number of samples per pixel (thereby halving the amount of noise) for free and if the framerate is high enough, the blurring isn't even that distracting. Setting the slider to 12 with just 4 spp results in a very high quality image (effectively more than 100 spp) at high framerates, but at the expense of lots of motion blur when the car or camera are moving
There are no acceleration structures used (not even a bounding box around the car or the robot). Implementing those should give a nice ray tracing performance boost.
I just saw a very impressive video on Youtube, showing real-time rendering of a complex interior scene with Octane Render using eight GTX 580s. Octane Render has very recently improved its "direct lighting/AO" kernel which includes a new ambient occlusion preset and a diffuse indirect lighting option (there are now separate sliders for specular, glossy and diffuse path depth and a slider for AO distance) so that it is now capable of rendering very realistic looking interior scenes extremely fast:
- in contrast to the type of scenes that is usually used to show off unbiased renderers (wide open outdoor scenes with shiny cars and lots of direct lighting from a skydome or sun/sky) this is an interior scene that is mostly lit by indirect lighting with many glossy surfaces
- the scene in the video contains more than 1.3 million triangles
- rendered at very high resolution (1500x1000 pixels)
- perfect scaling with number of GPUs (99-100% extra performance per additional GPU)
- while navigating through the scene, the image remains remarkably clear and recognizable without ever degenerating into a pixelated mess of big, blocky (and often black) pixels
- convergence to a noise-free image is extremely quick
It's not hard to imagine that this renderer will be truly real-time with the upcoming generation of GPUs (according to Nvidia, Kepler will be more than twice as fast at path tracing as Fermi, just like Fermi is 2-4x as fast as Tesla (GT200) thanks to caches and other improvements (see http://www.youtube.com/watch?v=0IC2NIogWR4) and AMD's Graphics Core Next will be much more focused on GPGPU computing than previous architectures). These graphics can be rendered noise-free in real-time at high resolution with techniques like adaptive sampling, image reconstruction, compressed sensing (a hot topic in medical imaging currently), edge-aware filtering of indirect lighting (e.g. the a-trous wavelet noise filter), extraction of spatiotemporal coherence with reprojection, path regeneration, reusing samples with frame averaging and frameless rendering. Rendering complex, 100% photorealistic scenes in real-time is much closer than commonly believed and cloud rendering will play a key role in accelerating this process.
UPDATE: another interior animation rendered on a Nvidia GTX 590 with Octane Render's new indirect diffuse lighting/AO kernel: http://www.youtube.com/watch?v=O2Aufjr44g4Hi Rendertime per frame: ~1 minute, 1024 samples per pixel (see screenshot in this thread). This is absolutely amazing...
I've changed the 'Unbiased Stunt Racer' demo a little bit: I've added the buildings from my Futuristic Buildings demo to the scene and also added a function to adjust the speed of the physics simulation at runtime with the N and M keys. The platform and sphere are also moving at a speed that's independent of the framerate, so the game is still playable on high-end cards like the GTX 480 and higher. The new executable contains 480p and 720p executables. I find it mindblowing that real-time path tracing is feasable today at HD resolutions using only one GPU.
Below is a 720p image of the new demo, rendered on a 8600M GT at 8 samples per pixel:
Some 480p screenshots (all captured on a 8600m GT):
A video will follow soon and the source code will also be uploaded. The code is very messy with lots of obsolete comments and there are heaps of global variables, which isn't good programming practice but it does the job. :)
This will be one of my last demos involving only spheres and boxes as primitives. The limitations on the number of objects and shapes are starting to outweigh the benefits of these cheap-to-intersect primitives, so I'm moving to the wonderful world of triangles and BVHs soon.
There is also a new paper and video on reducing Monte Carlo rendering noise called "Random parameter filtering" with amazing results (thanks to ompf.org forum): http://agl.unm.edu/rpf/ The video is definitely worth the download and shows great potential for real-time path tracing.
For the last couple of days, I've been busy creating "Unbiased Stunt Racer", a new real-time path traced demo involving physics, a vehicle and a shooting robot. It's actually a mix of a platformer and a stunt driving game. First you have to reach a platform by driving the vehicle over a ramp, then you have to reach another platform with a robot which is shooting at you, by driving over two rails where a nasty chrome sphere hinders the passage. The final goal is to push the robot off of his cosy place. The sunlight is constantly changing position and color, casting nice soft shadows over the scene. Below is a walkthrough video (rendered on GTS450) and some screenshots:
The number of samples per pixel can now be altered at runtime with the O and P keys. Pressing space resets the car. I've converted some of the stratified sampling in the original code back to purely random sampling, resulting in a slightly noisier but more realistic image.
The biggest advantage of using real-time ray tracing/path tracing for these "games" (besides having higher quality graphics) is that almost anyone can immediately start creating simple games without worrying about lighting, shadows, multiple reflections, refractions and all combinations of these effects. Everything just works as expected and without any effort on the artist side. It's like a "push button" game engine: just create the scene and the renderer takes care of everything else.
Changed the ground color and brightened up the sky in preparation for an upcoming demo called "Unbiased Stunt Racer" (courtesy of Anonymous blog reader :). It looks a little bit more realistic now (480p video on GTS 450):
