Merry Christmas to you all out there. Do you want to stress your computer a bit during the holidays.
Then please try our new Christmas path-tracing demo.
Cozy path tracing graphics from our lab.
Welcome to a day with talks on Accelerating Computations.
On 15 December 2011 the Computer Graphics Lab at the Alexandra Institute in Aarhus will host a conference on the core aspects of accelerating computations. This research conference will be divided into a technical part called Technical Talks in the morning and a business-oriented part called Applications Talks in the afternoon.
The conference is free and you can participate either in the Technical Talks, the Applications Talks or both. Keynote speaker will be David McAllister from NVIDIA.
The Computer Graphics Lab at the Alexandra Institute is working on realising efficient computations on massive data sets by using modern many-core processors and massive data algorithms. Subsequently
interactive information visualisation is crucial to analyse and understand massive data sets.
PROGRAMME
10:00- 10:15 Introduction
10:15 – 14:45 Technical Talks
10:15 – 11:00 How OptiX Makes the GPU Shine – a look inside NVIDIA’s Ray Tracing Engine, David McAllister, NVIDIA
11:00 – 11:45 MR reconstruction on GPU, Thomas Sangild, Computer Science, Aarhus University
11:45 – 12:30 Lunch
12:30- 13:15 Parthenon Renderer Revealed, Toshiya Hachisuka, Computer Science, Aarhus University
13:15- 13:45 Subsurface Light Propagation Volumes, Thomas Kim Kjeldsen, Computer Graphics Lab, Alexandra Institute
13:45 – 14:00 Coffee break
14:00 – 14:45 Accelerating Dense Linear Algebra on the GPU, Hans Henrik Brandenborg Sørensen, DTU Informatics
14:45 – 16:45 Applications Talks
14:45 – 15:15 Massive acceleration, Jesper Mosegaard, Computer Graphics Lab, Alexandra Institute
15:15 - 15:30 Coffee break
15:30 – 16:15 Dozens of Uses for Billions of Rays – a survey of ray tracing applications, David McAllister, NVIDIA
16:15 – 16:45 Scalable GPU computing service architecture: LEGO 3DServices, Henrik Høj Madsen, LEGO, Michael Schøler, Hinnerup.net.
16:45 – Networking and sandwiches
Venue: Alexandra Institute, Peter Bøgh Andersen Auditorium, building 5335, Finlandsgade 21-23, 8200 Aarhus N, Denmark
Registration: Online at http://cg.alexandra.dk/signup/
no later than 12 December
Abstracts
How OptiX Makes the GPU Shine – a look inside NVIDIA’s Ray Tracing Engine
David McAllister, Optix Manager, NVIDIA
I will briefly describe the OptiX programming model, then dive into the internals of how we exposed the
GPU’s computational power for ray tracing in an application programmable way.
MR reconstruction on GPU
Thomas Sangild Sørensen, Associate Professor, Computer Science, Aarhus University
A barrier to the adoption of non-Cartesian parallel magnetic resonance imaging for real-time applications has been the times required for the image reconstructions. These times have exceeded the underlying acquisition time thus preventing real-time display of the acquired images. We present a reconstruction algorithm for commodity graphics hardware (GPUs) to enable real time reconstruction of sensitivity encoded radial imaging (radial SENSE).
Parthenon Renderer Revealed
Toshiya Hachisuka, Assistant Professor, Computer Science, Aarhus University
Parthenon Renderer, initially released back in 2002, is one of the earliest publicly available rendering software that utilise graphics hardware for accelerating computation of high-quality offline rendering. I will talk about the inside of Parthenon Renderer in order to give you some examples of engineering choices and algorithm design that make (and made) sense for an offline rendering system using graphics hardware.
Subsurface Light Propagation Volumes
Thomas Kim Kjeldsen, Research and Innovation Scientist, Computer Graphics Lab, Alexandra Institute
We present the Subsurface Light Propagation Volume (SSLPV) method for real-time approximation of
subsurface scattering effects in dynamic scenes with changing mesh topology and lighting. SSLPV extends
the Light Propagation Volume (LPV) technique for indirect illumination in video games. We introduce a
new consistent method for injecting flux from point light sources into an LPV grid, a new rendering method
which consistently converts light intensity stored in an LPV grid into incident radiance, as well as a model for
light scattering and absorption inside heterogeneous materials. Our scheme does not require any precomputation
and handles arbitrarily deforming meshes. We show that SSLPV provides visually pleasing results
in real-time at the expense of a few milliseconds of added rendering time.
Accelerating Dense Linear Algebra on the GPU
Hans Henrik Brandenborg Sørensen, Post. Doc., GPU Lab, DTU Informatics
GPUs have already become an integral part of high performance scientific computing, since they offer
dedicated parallel hardware that can potentially accelerate the execution of many scientific applications.
In this talk, I will consider the automatic performance acceleration of dense vector and matrix-vector operations
on GPUs. Such operations form the backbone of level 1 and level 2 routines in the Basic Linear Algebra
Subroutines (BLAS) library and are therefore of great importance in many scientific applications. The target
hardware is the most recent NVIDIA Tesla 20-series (Fermi architecture). Most of the techniques I discuss
for accelerating dense linear algebra are applicable to memory-bound GPU algorithms in general.
Massive Acceleration at the Alexandra CG Lab
Jesper Bjerg Mosegaard, Head of Research and Innovation, Computer Graphics Lab, Alexandra Institute
The Computer Graphics Lab at the Alexandra Institute does research and development within the topic of
fast and accurate simulation and visualisation in high quality. This talk describes the role of the Alexandra
Institute in transferring research to application in Danish Industry as well as specific opportunities for
companies to benefit from the latest knowledge and technology.
Dozens of Uses for Billions of Rays – a survey of ray tracing applications
David McAllister, Optix Manager, NVIDIA
Since introducing OptiX in 2009, NVIDIA has been approached by engineers from industries as diverse as
geothermal exploration, cell phone antenna design, and automotive headlamp design that have one thing
in common – the need to intersect rays, usually billions of them, against a database of geometry. I will
survey many applications of ray tracing, within and beyond computer graphics, and show how accelerating
ray tracing using GPUs addresses many challenges in industry.
Scalable GPU computing service architecture: LEGO 3DServices
Michael Schøler, Hinnerup.net og Henrik Høj Madsen, Solution Architect, Lego
As LEGO is moving into the virtual playspace, a platform technology has been developed in-house primarily
based on NVIDIA technologies, featuring:
• CUDA, OptiX, OpenGL and general shaders
• 17 Quadro Plex in multiple environments, multiple datacentres
• Advanced shading techniques for approaching high-quality results in real-time
• On-demand asset generation
• CDN assets distribution
• A generic service-oriented interface
• A distributed rendering architecture
• Architectural patterns for distributed computing
• A plugin architecture supporting existing and future LEGO experiences
• A mentality shift from traditional ways of doing things on CPU vs GPU.
• General experiences from developing on NVIDIA tech in a large-scale Enterprise setup
The LEGO 3DServices system is designed to support diverse computational needs such as on-demand rendering, mesh optimisation, a Massive Multiplayer Online Game (MMO), product visualisations, 3D modeling and other current and future demanding computational tasks. Our aim with this session is to share our learnings and present LEGO’s vision of the future of distributed GPU accelerated computation as a business-driven platform technology.
We are proud to present a new release of our freeware surgical drilling simulator. That uses advanced volume ray casting and haptic force feedback to simulate a realistic drilling procedure in the temporal bone. This version has a complete drilling tutorial that guides the user through a whole masteodectomi.
Screenshot from VES showing the tutorial.
Notice the light green coloured bone structures, this indicates where the surgeon should drill. And the dark green coloured is used to display the bone that should have been drilled away in the previous steps.
More info can be found here http://ves.cg.alexandra.dk/
We are leaving for HPG and SIGGRAPH on Thursday. If you want to meet up with us, throw an e-mail at 
We have just had our paper on real-time subsurface scattering accepted for High-Performance Graphics 2011. The conference takes place August 5-7 in Vancouver. Here you can find a preprint of the paper which is titled SSLPV: Subsurface Light Propagation Volumes. Also we have provided a small demo along with the GLSL shader code.
Recently the Danish Ministry of the Interior and Health published a lot of key figures about Danish municipalities on a new web page ( http://www.noegletal.dk ). We put a little effort into making a pipeline capable of turning all those numbers into nice graphics. The figure seen above is an example of what our software can do. It is basically a bar diagram where each bar (or 'brick') is a municipality and the bar height and color encodes a quantity - here the population figure is shown.
Bunny rendered with area light, rendering time ca 8 min.
After Toshiyas visit we finally got around to implement a cuda version of his great progressive photon mapping.
It needs a lot of photons to converge, but it is really cool for caustics!
A teaser showing off our newest research project result on real-time subsurface scattering.
Steam shader effect
Feb 28
About a month ago we wrote about our shader-based heat shimmer effect. Another effect we developed for the Danfoss-experience project is illustrated in the video below. It tries to reproduce the effect of a window or mirror steaming up entirely as a shader.
Our method uses a gradient image 
which dictates the overall "growth" of the steam. A variable 
is animated over time from 0 to 2 and the amount of steam 
for a given position 
is then defined by a clamped linear interpolation over some range 
:
To make the growth more interesting, we modify with a noise texture. The color of the steam 
is determined from a lookup into a texture-rendered version of the scene which has been blurred by a Gaussian filter. To this value, we add some white noise to give the steam some texture. Finally, we add a value which can be tweaked to give the steam the desired amount of lightness.
The pixel color is then given by the unmodified color 
interpolated with the steam color:
The final touch to our effect, is the ability to interact with the steam by dragging the mouse around like a finger on the steamed up window. This is implemented by adding a mask texture and modifying the amount of steam by taking the minimum value of the mask and . The mask texture is updated by blending black lines into it where the mouse has been when it is being dragged around. Furthermore, a dark grey color is constantly blended into the entire mask in order to make the older strokes steam up again.
Our first Unity extension - Particle Director - just went live on the Unity Asset Store today. It is a tool for specifying custom particle velocities for particle systems. With it you are able to specify motion of the particles by placing control vectors, solids, sources, sinks, etc.
Check it out here.
