Multiscale 3D Reference Visualization  
Michael Glueck, Keenan Crane, Sean Anderson, Andres Rutnik, Azam Khan
To appear in i3D 2009 (ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games)
Abstract: Reference grids are commonly used in design software to help users to judge distances and to understand the orientation of the virtual workspace. However, despite their ubiquity in 3D graphics authoring applications, little research has gone into important design considerations of the 3D reference grids themselves, which directly impact their usefulness. In an effort to resolve some of these outstanding issues, we have developed two new techniques; the multiscale reference grid and position pegs that form a consistent foundation for presenting relative scale and position information to the user.
Our design of a multiscale reference grid consistently subdivides and coalesces gridlines, based on the computation of a closeness metric, while ensuring that there are neither too many nor too few subdivisions. Position pegs extend the grid so that objects that are lying above or below the ground plane can be brought into a common environmental frame of reference without interfering with the grid or object data. We introduce an analytical system, similar to MIP mapping, to provide a stable viewpoint-determined result. Our design solves several depth cue problems in a way that is independent of viewing projection.

Capturing and Animating Occluded Cloth  (project page)
Ryan White, Keenan Crane, David Forsyth
To appear in SIGGRAPH 2007
Abstract: We capture the shape of moving cloth using a custom set of color markers printed on the surface of the cloth. The output is a sequence of triangle meshes with static connectivity and with detail at the scale of individual markers in both smooth and folded regions. We compute markers' coordinates in space using marker correspondence across multiple synchronized video cameras. Correspondence is determined from color information in small neighborhoods and refined using a novel strain pruning process. Final correspondence does not require neighborhood information. We use a novel data driven hole-filling technique to fill occluded regions. Our results include several challenging examples: a wrinkled shirt sleeve, a dancing pair of pants, and a rag tossed onto a cup. Finally, we demonstrate that cloth capture is reusable by animating a pair of pants using human motion capture data.

Data Driven Cloth Animation  (project page)
Ryan White, Keenan Crane, David Forsyth
To appear in SIGGRAPH 2007 Technical Sketches
Abstract: We present a new method for cloth animation based on data driven synthesis. In contrast to approaches that focus on physical simulation, we animate cloth by manipulating short sequences of existing cloth animation. While our source of data is cloth animation captured using video cameras, the method is equally applicable to simulation data. The approach has benefits in both cases: current cloth capture is limited because small tweaks to the data require filming an entirely new sequence. Likewise, simulation suffers from long computation times and complications such as tangling. In this sketch we create new animations by fitting cloth animation to human motion capture data, i.e., we drive the cloth with a skeleton.

Real Time Simulation and Rendering of 3D Fluids  (project page)
Keenan Crane, Ignacio Llamas, Sarah Tariq
To appear in GPU Gems 3 (2007)
Abstract: Physically based animation of fluids such as smoke, water, and fire provides some of the most stunning visuals in computer graphics, but has historically been the domain of high-quality offline rendering due to great computational cost. In this chapter we not only show how these effects can be simulated and rendered in real time, but also how they can be seamlessly integrated into real time applications.

Rectangular Multi-chart Geometry Images  (project page)
Nate Carr, Jared Hoberock, Keenan Crane, John Hart
Proceedings of the 4th Eurographics Symposium on Geometry Processing, 2006
Abstract: Many mesh parameterization algorithms have focused on minimizing distortion and utilizing texture area, but few have addressed issues related to processing a signal on the mesh surface. We present an algorithm which partitions a mesh into rectangular charts while preserving a one-to-one texel correspondence across chart boundaries. This mapping permits any computation on the mesh surface which is typically carried out on a regular grid, and prevents seams by ensuring resolution continuity along the boundary. These features are also useful for traditional texture applications such as surface painting where continuity is important. Distortion is comparable to other parameterization schemes, and the rectangular charts yield efficient packing into a texture atlas. We apply this parameterization to texture synthesis, fluid simulation, mesh processing and storage, and locating geodesics.

Fast GPU Ray Tracing of Dynamic Meshes using Geometry Images  (project page)
Nate Carr, Jared Hoberock, Keenan Crane, John Hart
Proceedings of Graphics Interface 2006
Abstract: Using the GPU to accelerate ray tracing may seem like a natural choice due to the highly parallel nature of the problem. However, determining the most versatile GPU data structure for scene storage and traversal is a challenge. In this paper, we introduce a new method for quick intersection of triangular meshes on the GPU. The method uses a threaded bounding volume hierarchy built from a geometry image, which can be efficiently traversed and constructed entirely on the GPU. This acceleration scheme is highly competitive with other GPU ray tracing methods, while allowing for both dynamic geometry and an efficient level of detail scheme at no extra cost.

A Two-Color Map of Pluto's Sub-Charon Hemisphere  (project page)
Eliot Young, Richard Binzel, Keenan Crane
The Astronomical Journal, volume 121 (2001), pages 552-561
Abstract: Pluto and its satellite Charon regularly occulted or transited each other's disks from 1985 through 1990. The light curves resulting from these events (collectively called "mutual events") have been used to determine albedo maps of Pluto's sub-Charon hemisphere. We now use a data set of four light curves that were obtained in both B and V Johnson filters to construct a two-color map of Pluto's surface. We are able to resolve the central part of Pluto's sub-Charon hemisphere. We find that the dark albedo feature that forms a band below Pluto's equator is comprised of several distinct color units. We detect ratios of V-filter/B-filter normal reflectances ranging from 1.15 to 1.39 on Pluto's sub-Charon hemisphere.  

Manuscripts

A Survey of Efficient Structures for Digital Geometry Processing  (project page)
Keenan Crane
Manuscript, University of Illinois at Urbana-Champaign, April 2006
Abstract: In recent years, massive surface datasets have inspired the development of out-of-core (OoC) algorithms that process surfaces in a spatially coherent order. This reformulation of surface processing yields mesh data structures which are more cache-friendly than prior representations. Although OoC techniques are intended to mask high latency disk access, the same principles can benefit processing in other levels of the cache hierarchy. This survey gives a background on traditional geometry processing, examines the development of OoC mesh processing algorithms, and briefly considers the potential of OoC-like data structures for parallel- and stream-processing.