Greg Coombe

Physically-based visual simulation on graphics hardware

In this paper, we present a method for real-time visual simulation of diverse dynamic phenomena using programmable graphics hardware. The simulations we implement use an extension of cellular automata known as the coupled map lattice (CML). CML represents the state of a dynamic system as continuous values on a discrete lattice. In our implementation we store the lattice values in a texture, and use pixel-level programming to implement simple next-state computations on lattice nodes and their neighbors. We apply these computations successively to produce interactive visual simulations of convection, reaction-diffusion, and boiling. We have built an interactive framework for building and experimenting with CML simulations running on graphics hardware, and have integrated them into interactive 3D graphics applications.In this paper, we present a method for real-time visual simulation of diverse dynamic phenomena using programmable graphics hardware. The simulations we implement use an extension of cellular automata known as the coupled map lattice (CML). CML represents the state of a dynamic system as continuous values on a discrete lattice. In our implementation we store the lattice values in a texture, and use pixel-level programming to implement simple next-state computations on lattice nodes and their neighbors. We apply these computations successively to produce interactive visual simulations of convection, reaction-diffusion, and boiling. We have built an interactive framework for building and experimenting with CML simulations running on graphics hardware, and have integrated them into interactive 3D graphics applications.

Fast Summed-Area Table Generation and its Applications

We introduce a technique to rapidly generate summed-area tables using graphics hardware. Summed area tables, originally introduced by Crow, provide a way to filter arbitrarily large rectangular regions of an image in a constant amount of time. Our algorithm for generating summed-area tables, similar to a technique used in scientific computing called recursive doubling, allows the generation of a summed-area table in O(log n) time. We also describe a technique to mitigate the precision requirements of summed-area tables. The ability to calculate and use summed-area tables at interactive rates enables numerous interesting rendering effects. We present several possible applications. First, the use of summed-area tables allows real-time rendering of interactive, glossy environmental reflections. Second, we present glossy planar reflections with varying blurriness dependent on a reflected object’s distance to the reflector. Third, we show a technique that uses a summed-area table to render glossy transparent objects. The final application demonstrates an interactive depth-of-field effect using summedarea tables.

Artistic Vision: painterly rendering using computer vision techniques

We present a method that takes a raster image as input and produces a painting-like image composed of strokes rather than pixels. Our method works by first segmenting the image into features, finding the approximate medial axes of these features, and using the medial axes to guide brush stroke creation. System parameters may be interactively manipulated by a user to effect image segmentation, brush stroke characteristics, stroke size, and stroke frequency. This process creates images reminiscent of those contemporary representational painters whose work has an abstract or sketchy quality. Our software is available at http://www.cs.utah.edu/npr/ArtisticVision.

Radiosity on graphics hardware

Radiosity is a widely used technique for global illumination. Typically the computation is performed offline and the result is viewed interactively. We present a technique for computing radiosity, including an adaptive subdivision of the model, using graphics hardware. Since our goal is to run at interactive rates, we exploit the computational power and programmability of modern graphics hardware. Using our system on current hardware, we have been able to compute and display a radiosity solution for a 10,000 element scene in less than one second.

Online construction of surface light fields

We present a system for interactively capturing, constructing, and rendering surface light fields by incrementally building a low rank approximation to the surface light field. Each image is incorporated into the lighting model as it is captured, providing the user with real-time feedback. This feedback enables the user to preview the lighting model and direct the image acquisition towards undersampled areas of the object. We also provide a novel datadriven quality heuristic to aid the user in identifying undersampled regions. Our system is an order of magnitude faster than previous systems, and reduces the time necessary to capture the images and construct a surface light field from hours to minutes.

An Incremental Weighted Least Squares Approach to Surface Lights Fields

An Image-Based Rendering (IBR) approach to appearance modelling enables the capture of a wide variety of real physical surfaces with complex reflectance behaviour. The challenges with this approach are handling the large amount of data, rendering the data efficiently, and previewing the model as it is being constructed. In this paper, we introduce the Incremental Weighted Least Squares approach to the representation and rendering of spatially and directionally varying illumination. Each surface patch consists of a set of Weighted Least Squares (WLS) node centers, which are low-degree polynomial representations of the anisotropic exitant radiance. During rendering, the representations are combined in a non-linear fashion to generate a full reconstruction of the exitant radiance. The rendering algorithm is fast, efficient, and implemented entirely on the GPU. The construction algorithm is incremental, which means that images are processed as they arrive instead of in the traditional batch fashion. This human-in-the-loop process enables the user to preview the model as it is being constructed and to adapt to over-sampling and under-sampling of the surface appearance.

SKIT: a computer-assisted sketch instruction tool

In a visual world, the ability to sketch is an important asset for communicating complex ideas. However, sketching is a frustrating task for many people, and most never progress beyond a rudimentary skill level. In this paper we present SKIT, a computer-assisted sketch instruction tool. SKIT attempts to teach beginning students one of the important skills of sketching, the ability to perceive effectively. It is based on traditional art instruction techniques, which break the complex task of drawing into smaller tasks. These sub-tasks are combined into a final drawing, which can be then rendered using several different NPR styles. We also present preliminary results from people who have used SKIT.