Friday, December 30, 2011

Videos and executable demo of Brigade 2 GUI and animation test

Some videos of the GUI that I developed for Brigade 2, showing real-time changing of materials with simultaneous animation and physics simulation. The GUI is still a work in progress, but being able to tweak any material on the fly is so much more easy to get the look right.

480p (320x240 render res, 4 spp, max depth 4)

480p (640x480 render res, 4 spp, max depth 4)

The Ogre (model from here) is just simply rotating for now. The mesh consists of 51k triangles of which the BVH is dynamically updated every frame (as are the BVHs of the car and the stack of blocks which are physics driven). 

The executable demo is available at 

Further experiments will include: 
- skeletal animation
- first person camera and gun
- cam following the vehicle
- architecture 

Thursday, December 29, 2011

GUI test in Brigade 2

I've been working on a IMGUI (immediate mode GUI) for Brigade 2 based on SDL, which is working pretty well and is quite responsive when the framerate is more than 5 fps. There are sliders for specularity, transparency and RGB values of the diffuse color of the material. Every material in the scene can be picked and updates in real-time + you can navigate the scene, control the vehicle and let a physics simulation run, all simultaneously while chaning materials. I will upload an executable demo and some videos of the GUI in action tomorrow.

Screenshot of the GUI while tweaking a glossy Ogre (almost 50k triangles, model from Javor Kalojanov's real-time raytraced animation demo):

szczyglo74 (CG artist/architect) also provided me with a modern half-open architectural structure (Altana model from Januszowka) which is great to test indirect lighting and which I will turn into a demo soon (screen rendered on 8600M GT): 

Paper + video of "Real-time bidirectional path tracing via rasterization"

Available here:  (thanks to selfshadow)

It looks pretty damn good and the technique seems to be a very likely candidate for implementation in next-gen games because it fully exploits the rasterization hardware. One of the limitations (as mentioned in the paper) is that it doesn't work well for highly glossy and perfectly specular surfaces (sharp reflections) for which ray tracing is proposed as an alternative.

Monday, December 26, 2011

Real-time bidirectional path tracing via rasterization

This is the title of an upcoming I3D 2012 paper by Yusuke Tokuyoshi and Shinji Ogaki, see

The title reminds me of "High-quality global illumination rendering using rasterization" by Toshiya Hachisuka from 2005, which described a technique to obtain photorealistic images on a typical 2005 GPU (like the Radeon 9700) in mere seconds, extremely impressive for that time. Shinji Ogaki is also a co-author on the Progressive Photon Mapping paper by Hachisuka and Jensen, so this new paper is definitely going to be interesting.

If the paper lives up to the title, this could be quite interesting. Both researchers work at Square Enix and there seems to be a connection with the recently unveiled photorealistic Luminous engine which uses high quality offline baked lightmaps (see this page for more details). A paper about the rasterization-based lightmap baking in Luminous can be found here and the real-time bidirectional PT technique probably works very similarly (i.e. ray bundles computed with rasterization by parallel visibilty tests):

Quote from the "Fast global illumination baking via ray bundles" paper (describing the tech behind the Luminous engine):
7 high-quality light maps are rendered in 181 seconds with NVIDIA GeForce GTX 580. The resolution of ray-bundle is 2048x2048 pixels, and 10000 directions are sampled. The performance of our renderer is over 200 M rays per second on a commodity GPU.
Assuming everything scales linearly, this means that it would take about 16 milliseconds (60 fps) on a GTX 580 to compute a GI lightmap with ray bundles of 512x512 pixels and 100 ray bundle directions (= 100 directional samples) which should still yield great quality real-time global illumination. This tech could potentially be used for making real-time photorealistic games on current GPUs. It doesn't work however for objects with highly glossy and perfectly specular materials.

Wednesday, December 21, 2011

Executable for Brigade 2 vehicle physics test available

An executable demo of the scene in the previous post is available at

I've recompiled the cuda binaries on my laptop for every possible CUDA GPU architecture (compute capability 1.0, 1.1, 1.2, 1.3, 2.0 and 2.1). Since the binaries were not natively compiled on their respective architecture and use a fixed maxregistercount of 63, higher end GPUs like the GTX 560 and up are not used to their fullest potential (a member of the Beyond3D forum reports only 35% GPU load on a GTX 460 with this demo). But at least it works on all CUDA architectures :-)

UPDATE: Roeny (one of Brigade's developers) has posted an explanation of why the GPU is not fully loaded here:

UPDATE 2: szczyglo74 has posted a cool video on Youtube of the 480p demo on a GTX 590 + GTX 460 (3 GPUs in total!)

Tuesday, December 20, 2011

Brigade 2 Glossy test 480p and 720p videos on GTS 450

Some videos of the scene in the previous post:


- rendered on just one GTS 450, no CPUs involved (hybrid CPU/GPU rendering is actually slower than pure GPU rendering (due to synching) besides being more complex)
- 640x480 render resolution (first video)
- 1280x720 HD render resolution (second video)
- extremely fast convergence: great image quality with only 4 samples per pixel per frame (when the camera is non-stationary) which is sufficient for scenes with skydome lighting
- max path depth 4
- floor, blue boxes, vehicle wheels and chassis are partially glossy to create a plastic look
- containers, mirror ball and flat mirror are perfectly specular
- orange ball is perfectly refractive in first video
- walls are perfectly diffuse (Lambertian)
- almost 3800 triangles (not that many but it's a lot less restrictive than the spheres and boxes from TOKAP and actually not that much slower thanks to BVH acceleration) 

The framerate would be a lot smoother on a GTX 580, or better yet a pair of them :-)

Monday, December 19, 2011

Glossy test in Brigade 2

Some screenshots of a new Brigade 2 powered demo that I'm working on (rendered with a 8600M GT at 640x360). The floor is textured and slightly glossy and almost every object in the scene is fully or partially specular e.g. the blue boxes in the stack and the wheels and body of the vehicle now have a plastic look. The scene looks great in motion. Videos on a GTS 450 will follow tomorrow. 

Sunday, December 18, 2011

480p and 720p videos of Brigade 2 physics and UI tests on the GTS 450

The following videos demonstrate some Bullet physics tests that I've been working on and which were rendered in real-time with the Brigade 2 path tracer on a GeForce GTS 450. All the rendering is pure GPU path tracing with CUDA, the CPU doesn't take part in the rendering process except for recalculating the dynamic BVH of the car and the boxes every frame. All the light in the scene is coming from a skydome. The code for the car physics is essentially the same as what was used in the "Unbiased Stunt Racer" demo. The physics simulation can be paused and resumed and the image converges (extremely fast) when nothing moves (physics simulation paused + stationary camera). There is also a short demo of a work-in-progress material UI (only diffuse to glossy/specular for now, the final version will have sliders for transparency, specularity, diffuse color and emissive color).

480p physics test (640x480 screen resolution, 320x240 render resolution):

480p UI test (640x480 screen resolution, 320x240 render resolution):

480p UI test (640x480 screen and render resolution) watch on youtube in 480p:

720p UI test (1280x720 screen resolution and render resolution!) watch on Youtube in 720p:

Wednesday, December 14, 2011

Physics tests in Brigade 2

Jeroen van Schijndel, one of the developers of the Brigade path tracer, has posted a cool video showing off the physics inside Brigade:

During the last several days, I have been working on implementing vehicle physics in a new simple demo that uses the Brigade 2 path tracer. The scene in the demo is only lit by a sky texture and consists of a vehicle with mass, a few perfectly specular containers and a stack of boxes (more than 2800 triangles in total). The maximum path depth is 4 to make the reflections more interesting.

The following screenshots and videos were all rendered in real-time on a mobile GPU, the 8600M GT, which is extremely low-end by today's standards and is about 30 times slower than a GTX 580. Nevertheless, despite its very low "CUDA core" count and clocks, it can still produce some pretty amazing footage, path-traced in real-time at 4 samples per pixel and a max path depth of 4 (allowing for reflections of reflections). Better videos with much higher framerate (captured on a GTS 450) will follow soon.

Somewhat better quality, but lower framerate

4 spp, 480x360

Glossy floor, 4 spp

24 spp, 480x360:

Some ideas that I want to work on next:

- frame averaging, which greatly reduces the noise at the expense of slight blurring
- a camera that follows the vehicle automatically
- a first-person gun which can shoot projectiles with physical mass
- (low-poly) animated enemies (with cheap-to-update BVH)
- investigate the use of bump mapping to further increase realism (Dade's Sfera demo has shown that bump mapped surfaces converge almost as fast as non-bump mapped ones)
- more interesting scenes, using a greater variety of materials (Brigade supports diffuse, glass, glossy and perfectly specular) and textures. I'm still aiming to replicate this path traced animation in real-time

The Brigade 2 path tracer is just great fun to play with and the speed and quality in a well-lit environment (on a high end GPU) are truly amazing. Seeing a real-time animated character with perfectly photoreal lighting while orbiting the camera around it is so damn rewarding...

Saturday, December 10, 2011

Sfera, the first real-time path traced game based on OpenCL!

This is very cool: there is a new game called Sfera, it's using only spheres and is rendered with real-time path tracing on the GPU and CPU using OpenCL. The developer of the game, Dade (David Bucciarelli), is a LuxRender developer who is the first to make a working implementation of OpenCL-based unbiased path tracing on ATI cards. He created SmallptGPU, SmallLuxGPU and LuxRays.

Youtube video of the Sfera game:

The demo features HDR image based lighting, bump mapping, multiple physically accurate materials, Bullet physics and multi-GPU support. I think it is absolutely awesome to see more developers using the power of the GPU (I'm glad that this time OpenCL and GPUs from ATI are used) to create amazing looking simple games with real-time photorealistic lighting. This game is a very nice proof-of-concept to show that real-time photorealism is very close. I hope this is the beginning of a paradigm shift for game graphics from rasterization to real-time ray tracing. The code is also open source and can be found at (includes executables for Windows and Linux).

More info about the game Sfera can be found at

Btw, thanks Dade for mentioning Tokap and my blog on Sfera's project page ;-)

Friday, December 9, 2011

Vehicle test in Brigade 2

Another test with the Brigade 2 path tracer: this time I've added a user-controllable vehicle (included in Brigade) to the scene from the previous post. The truck consists of 1953 triangles and uses a dynamic BVH which is updated (BVH refitting as there are only translations and rotations) every frame when the truck moves.

There is also some variation in the materials (all objects are no longer diffuse): the horse has a glass material applied to it (no Beer's law, although the engine supports it), the green sphere is glossy and the truck's trailer is perfectly specular. The following video and screenshots were rendered at 320x240 with 12 spp per frame on a low-end GPU (GeForce GTS 450):

The shadows and refraction are awesome:

640x480 render resolution:

Some ideas for upcoming tests:

- recycle the vehicle physics code from the Unbiased Stunt Racer demo
- move to an outdoor environment with skydome lighting. From early trials I've found out that the convergence in such a setting is extremely fast and 8 spp are often enough
- make a real-time Bullet physics demo of a collapsing structure, e.g. something like this or this

Wednesday, December 7, 2011

Bullet physics test 1 in Brigade 2

I've made a very simple real-time, interactive Bullet physics simulation of a bouncing light-emitting cube, rendered using the Brigade 2 path tracer with 8 spp per frame on a low-end GTS 450 (render resolution is 320x240 to keep the framerate acceptable). The simulation can be paused and resumed and the image converges when nothing moves. The scene contains 12733 triangles.


Thursday, December 1, 2011

Real-time path traced outdoor scene with Brigade 2 engine

Jacco Bikker has just posted a gorgeous looking new video of a WIP game oozing with atmosphere, which is running on the real-time path tracer Brigade 2:

A downloadable direct feed version (strongly recommended) can be found here:

The video description says it all:
"This is some early footage from the student game "It's About Time", created by students of the IGAD program of the NHTV university of applied sciences, Breda, The Netherlands. This game uses the Brigade 2 path tracer for rendering. Although this results in a noisy image, the lighting is very realistic. A proof-of-concept demo of the game will be ready in January 2012. After that, the team intends to continue working on the project until the end of the academic year."

Some screengrabs from the video:
Note the ambient occlusion under the cylindrical stones and the greenish color bleeding on them

Sun + Sky lighting:

The lighting in the video is of the same quality as a precomputed lightmap, but is completely real-time. Obviously there is still some noise, most visible in indirectly lit parts of the scene, but I personally think it adds a special touch to the image, while at the same time attesting to the "real-timeness" of the lighting. The Brigade engine will truly shine when moving objects and animated characters will be added, which will both receive and radiate the same "perfect" physically based lighting as their environments. Moreover, this scene is just showing diffuse materials, but Brigade 2 can handle materials such as glass (with physically based light attenuation according to Beer's law), glossy (Blinn shader) and perfectly specular effortlessly, as proven in the videos in this post.

In the image below, notice the indirect lighting with brownish color bleeding under the wooden roof.

Today's games use a variety of tricks to approximate indirect lighting, such as high quality precomputed lightmaps (e.g. RAGE from id Software, Mirror's Edge from D.I.C.E.), instant radiosity (e.g. Geomeric's Enlighten technology in Battlefield 3, Lightsprint in Rockstar's L.A. Noire), cascaded light propagation volumes (LPV) with screen space GI (Crysis 2) and point based color bleeding (Danger Planet tech demo from Fantasy Labs, based on Michael Bunnell's surfel technique which was also used in Pixar's Up and in Pirates of the Caribbean). Each of these techniques has its own drawbacks:

- full or partial precomputation of lighting,
- limited scene destructability,
- real-time hard shadows superimposed over high quality, prebaked soft shadows resulting in an ugly shadow mix (RAGE and Mirror's Edge are nice examples)
- limited number of bounces
- crudely approximated, diffuse only indirect lighting
- no influence from the color of dynamic objects on the environment (e.g. a red wall will cast a reddish glow on a nearby white barrel, but a red explosive barrel near a white wall will do nothing)
- time consuming artist intervention (e.g. manual light probe placement in areas of interest)

While it's great to see that some games are finally implementing real-time GI approximations, they are still hacks that start to break when mirrors, glass and highly glossy objects are added to the scene. Real-time path tracing solves all these issues in one breath. While the performance on one current high-end GPU is still not sufficient, very nice looking real-time path traced prototypes (with animation) are already possible, giving a glimpse of where game graphics are headed when GPU clusters in the cloud come into play.

Right now, I'm busy working on some Brigade 2 powered real-time demo's (with Bullet physics) which I hope to show very soon.

Monday, November 28, 2011

Temporary solution for Ompf forum

Since the 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:

UPDATE: there's an interesting discussion and technical details on the improvements in the Brigade path tracer in this topic

Friday, November 25, 2011

New videos of Brigade!

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.

Thursday, November 17, 2011

CentiLeo paper available

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: (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.

Friday, November 4, 2011

Photorealistic animation rendered with Octane Render from within 3ds Max UPDATE: new video of Octane/3ds Max integration

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.

UPDATE: a new video appeared on the Octane Render forum, showing fully integrated Octane in the 3ds Max environment:

Wednesday, October 26, 2011

Update 2 on Exposure Render

There is now a stable release of Exposure Render, the open source direct volume renderer with physically based lighting on the GPU:

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):

Friday, October 21, 2011

OTOY partners with Autodesk to stream real-time path traced graphics from the cloud

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.

VentureBeat article (includes an image of Octane's subsurface scattering implementation):

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.

One of the images in the VentureBeat article looks like the Kajiya scene (which can now be rendered at more than 10 fps with the Brigade engine, including caustics) in an IBL environment:

Very cool!

Tuesday, October 18, 2011

Real-time path tracing of animated meshes on the GPU (2): OGRE

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 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.

Friday, October 14, 2011

Real-time path tracing of animated meshes on the GPU (1)

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):

Details will follow.

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):

Thursday, October 13, 2011

Update on Exposure Render

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:

Someone has also put the video from the paper "On filtering the noise from the random parameters in Monte Carlo rendering" on Youtube, making it more convenient to retrieve and watch:

The results for filtered images using only 8 input samples per pixel are extremely impressive.

Tuesday, October 4, 2011

Unbiased subsurface scattering on the GPU in next version of Octane Render

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 :-)

Saturday, October 1, 2011

Real-time physically based volume rendering with CUDA

Just saw a very impressive video of "Exposure Render", an open source CUDA based volumetric path tracer which will be presented at EuroGraphics 2012:

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.

An executable and source code (Oct 3rd) are available at

Thursday, September 29, 2011

In-depth video on micropolygons in OpenGL

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":

Lots of interesting insights in the future of GPU hardware.

Tuesday, September 27, 2011

Real-time dynamic GPU path tracing

A small teaser of something I'm working on, rendered in real-time on a GeForce GTS 450:

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 details on Imagination's PowerVR GPU with Caustic Graphics hardware ray tracing

A few days ago, an article appeared on the Japanese website 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:

Saturday, September 24, 2011

Video of Unbiased FPS + a new video of Brigade!

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:

On a sidenote, I found a new, short video of the Brigade path tracer, showing a real-time pathtraced animated character: (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).

Wednesday, September 21, 2011

Unbiased FPS

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.

Monday, September 12, 2011

Video of Octane Render rendering in real-time on 8x GTX580s

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:

Screengrab from Youtube:

Some observations:

- 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 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:
Rendertime per frame: ~1 minute, 1024 samples per pixel (see screenshot in this thread). This is absolutely amazing...

Wednesday, September 7, 2011

Unbiased Stunt Racer in HD!

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. :)

The executable "Unbiased Stunt Racer HD Final" is available at

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.

UPDATE: source code is online at

UPDATE 2: sneak peek at an upcoming demo (robot and car will be user controlled and "shootable")

UPDATE 3: Finally found some time to make an HD video of Unbiased Stunt Racer HD:

720p "fly-through":

480p gameplay:

Executable and source can be found at

There is also a new paper and video on reducing Monte Carlo rendering noise called "Random parameter filtering" with amazing results (thanks to forum): The video is definitely worth the download and shows great potential for real-time path tracing.