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.