Computer Graphics
TU Braunschweig


Talk High Dynamic Range Imaging and Display

06.03.2007 14:00
Informatikzentrum, Seminarraum G30

Speaker(s): Wolfgang Heidrich

The human visual system's ability to process wide ranges of intensities by far exceeds the capabilities of current imaging systems. Both cameras and displays are currently limited to a dynamic range (contrast) of between 300:1 to 1,000:1, while the human visual system can process a simultaneous dynamic range of 50,000:1 or more, and can adapt to a much larger range.

High-dynamic-range (HDR) imaging refers to the capture, processing, storage, and display of images with significantly improved contrast and brightness compared to the conventional imaging pipeline. This new HDR imaging pipeline is designed to match the power of the human visual system. HDR displays significantly improve the sense of realism and immersion when showing both real and synthetic HDR imagery. Likewise, HDR cameras are able to take images without saturation under difficult lighting situations. The additional information captured in both extremely bright and extremely dark regions is useful as an input for HDR displays, but also for machine vision applications.

In this talk, I will summarize the results of a multi-disciplinary research effort to create the first true HDR display. This work is a collaboration of multiple departments at The University of British Columbia, and a spin-off company called Brightside Technologies. I will provide an overview of current research activities, with a focus on computational problems.

Talk Eikonal Rendering

22.12.2006 11:00
Informatikzentrum, Seminarraum G30

Speaker(s): Ivo Ihrke

In this talk, I present an interactive rendering method for refractive objects. The refractive index is allowed to vary continouosly, and total reflection is taken into account. The method is based on set of ordinary differential equations that are derived from the eikonal equation, the main postulate of ray optics. This set of equation allows for ray casting of bent light rays with the complexity of a particle tracer.

Talk A Framework for Holographic Scene Representation

19.10.2006 13:00
Informatikzentrum, Seminarraum G30

Speaker(s): Gernot Ziegler

At ETH we developed a framework for holographic representation and display of graphics objects. As opposed to traditional graphics representations, our approach reconstructs the light wave reflected or emitted by the original object directly from the underlying digital hologram. Our novel holographic graphics pipeline consists of several stages including the digital recording of a full-parallax hologram, the reconstruction and propagation of its wavefront, and rendering of the final image onto conventional, framebuffer-based displays. The required view-dependent depth image is computed from the phase information inherently represented in the complex-valued wavefront. Our model also comprises a correct physical modelling of the camera taking into account optical elements, such as lens and aperture. It thus allows for a variety of effects including depth of field, diffraction, interference and features built-in anti-aliasing. A central feature of our framework is its seamless integration into conventional rendering and display technology, which enables us to elegantly combine traditional 3D object or scene representations with holograms.

Talk Gaussian curvature on polyhedral surfaces

22.08.2006 14:00
Informatikzentrum, Seminarraum G30

Speaker(s): Anita Sellent

The Gaussian curvature of a regular surface is a well-known term in differential geometry; there are even several equivalent ways to define it. Gauss himself defined this curvature via the normal image. In the presentation this definition is transferred to polyhedral surfaces: Though the procedure is obvious for convex vertices it causes some difficulties for non-convex vertices. A method to calculate the normal image for some of the non-convex vertices is presented which on the one hand confirms the angle-deficit as polyhedral Gaussian curvature and on the other hand bears further information on the vertices. In conclusion some of the fundamental theorems for the continuous Gaussian curvature can be affirmed for its polyhedral analogue.

Talk Boosting Restricted to Integer Lattices

18.07.2006 14:00
Informatikzentrum, Seminarraum G30

Speaker(s): Dirk Breitenreicher

When classifying a set of samples into various classes in most cases one highly complex optimization problem has to be solved. A boosting approach, in contrast, is able to determine multiple weak learners such that their combination is as accurate as the single, strong classification rule. Often these weak learners are easier to obtain than the solution of the complex optimization problem. However, finding weak learners that can be used for boosting is a not trivial task. Obtaining multiple weak learning rules may also require a lot of time and memory. Classifying on integer lattices can address this problem. When using classifiers on integer lattices each weak learner is build up on integer variables exclusively. This causes that the training and the evaluation time as well as the required memory decreases dramatically in most cases.

Talk Automatic Creation of Object Hierachies for Ray tracing of Dynamic Scenes

26.04.2006 14:00
Informatikzentrum, Seminarraum G30

Speaker(s): Martin Eisemann

Ray tracing acceleration techniques most often consider only static scenes, neglecting the processing time needed to build the acceleration data structure. With the development of interactive ray tracing systems, this reconstruction time becomes serious bottleneck if concerned with dynamic scenes. I am going to describe two strategies for efficient updating of bounding volume hierarchies (BHV) for scenarios with arbitrarily moving objects. The first exploits spatial locality in the object distribution for faster reinsertion of the moved objects. The second allows insertion and deletion of objects at almost constant time by using a hybrid system, which combines benefits from both spatial subdivision and BHVs. Depending on the number of moving objects, the algorithms adjust a dynamic BHV six to one hundred times faster than it would take to rebuild the complete hierarchy, while rendering times of the resulting hierarchy remains almost untouched.