John C. Hart

University of Illinois, Urbana-Champaign | UIUC · Department of Computer Science

Sustainable crop production is a contributing factor to current and future food security. Innovative technologies are needed to design strategies that will achieve higher crop yields on less land and with fewer resources. Computational modeling coupled with advanced scientific visualization enables researchers to explore and interact with complex a...

Lagrangian coherent structures provide insight into unsteady fluid flow, but their construction has posed many challenges. These structures can be characterized as ridges of a field, but their local definition utilizes an ambiguous eigenvector direction that can point in one of two directions, and its ambiguity can lead to noise and other problems....

Multi-scale models can facilitate whole plant simulations by linking gene networks, protein synthesis, metabolic pathways, physiology, and growth. Whole plant models can be further integrated with ecosystem, weather, and climate models to predict how various interactions respond to environmental perturbations. These models have the potential to fil...

Tracing the paths of collections of particles through a flow field is a key step for many flow visualization and analysis methods. When a flow field is interpolated from the nodes of an unstructured mesh, the process of advecting a particle must first find which cell in the unstructured mesh contains the particle. Since the paths of nearby particle...

We present a botanical simulation of secondary (cambial) tree growth coupled to a physical cracking simulation of its bark. Whereas level set growth would use a fixed resolution voxel grid, our system extends the deformable simplicial complex (DSC), supporting new biological growth functions robustly on any surface polygonal mesh with adaptive subd...

We present a system for monitoring the engagement of remote students in an online educational environment. We introduce a novel gaze estimation system that uses a client-side video-based 3D face tracking algorithm, and expands it to estimate the head pose, and intersects this pose-based gaze line of sight with the screen (coplanar with the camera)...

Modern object detection methods apply binary linear classifiers on Euclidean feature vectors. This paper shows that projecting feature vectors onto a hypersphere allows an approximate range query to accelerate these detectors within acceptable levels of accuracy. The expense of constructing the k-d tree used by these range queries is justified when...

This chapter proposes an improved edge-parallel approach for computing centrality metrics that can also accelerate breadth-first search and all-pairs shortest path. For some graph algorithms such as computing centrality, breadth-first search, and even all-pairs shortest path, an edge-parallel approach improves graphical processing unit (GPU) throug...

InvertNet aims to support digitization and delivery of specimen-level data and images for invertebrate collections, beginning with 22 arthropod collections in the midwestern USA. The project is implementing high-throughput digitization workflows that reduce the per-specimen cost of digitization while protecting specimens from unnecessary handling....

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InvertNet, one of the three Thematic Collection Networks (TCNs) funded in the first round of the U.S. National Science Foundation's Advancing Digitization of Biological Collections (ADBC) program, is tasked with providing digital access to ~60 million specimens housed in 22 arthropod (primarily insect) collections at institutions distributed throug...

The visibility complex organizes the space of maximal seg-ments in the free-space of a 3-D scene into a four-dimensional structure. The cells of the visibility complex have applications in image-based ren-dering, form-factor computations, global illumination, shadowing and many other methods, but to date only the 0-D and 1-D cells have been constru...

The hierarchical edge bundle (HEB) method generates useful visualizations of dense graphs, such as social networks, but requires a predefined clustering hierarchy, and does not easily benefit from existing straight‐line visualization improvements. This paper proposes a new clustering approach that extracts the community structure of a network and o...

The classification of 3d point cloud data is an important component of applications such as map generation and architectural modeling. However, the complexity of the scenes together with the level of noise in the data acquired through mobile laser range-scanning make this task quite difficult. We propose a novel classification method that relies on...

Panoramic images capture cityscapes of dense urban structures by mapping multiple images from different viewpoints into a single composite image. Once challenge to their construction is that objects that lie at different depth are often not stitched correctly in the panorama. The problem is especially troublesome for objects occupying large horizon...

We present MethMorph, a system for producing realistic simulations of how drug-free people would look if they used methamphetamine. Significant weight loss and facial lesions are common side effects of meth usage. MethMorph fully automates the process of thinning the face and applying lesions to healthy faces. We combine several recently-developed...

While many algorithms exist for tracing various contours for illustrating a meshed object, few algorithms organize these contours into region-bounding closed loops. Tracing closed-loop boundaries on a mesh can be problematic due to switchbacks caused by subtle surface variation, and the organization of these regions into a planar map can lead to ma...

As an emerging technology, D video has shown a great potential to become the next generation media for tele-immersion. However, streaming and rendering this dynamic 3D data in real-time requires tremendous network bandwidth and computing resources. In this paper, we build a remote rendering model to better study different remote rendering designs a...

The hierarchical edge bundle method clusters the edges of a radial layout to better understand and analyze graphs, but its effectiveness relies critically on the quality of the hierarchical organization of its nodes and edges. This paper proposes a novel graph visualization approach that extracts the community structure of a network and organizes i...

Abstract We present a generalization of the scalar importance function employed by Metropolis Light Transport (MLT) and related Markov chain rendering algorithms. Although MLT is known for its user-designable mutation rules, we demonstrate that its scalar contribution function is similarly programmable in an unbiased manner. Normally, MLT samples l...

The k-D tree is a well-studied acceleration data structure for ray tracing. It is used to organize primitives in a scene to allow efficient execution of intersection operations between rays and the primitives. The highest quality k-D tree can be obtained using greedy cost optimization based on a surface area heuristc (SAH). While the high quality e...

The level set method can implement a wide variety of shape modeling operations (e.g. offsetting, skeletonization, morphing, blending, smoothing, sharpening, embossing, denoising, sculpting, growing, texturing and fitting) simply by specifying a corresponding speed function that controls the growth of an evolving voxel isosurface. The problem is tha...

Geometry images resample meshes to represent them as texture for efficient GPU processing by forcing a regular parameterization that often incurs a large amount of distortion. Previous approaches broke the geometry image into multiple rectangular or irregular charts to reduce distortion, but complicated the automatic level of detail one gets from M...

Internet attacks are on the rise and pose serious security threats to enterprise networks, commercial websites and to the millions of home internet users. Internet attacks are becoming more potent and complex with time. Network traffic visualization tools have suc-cessfully enabled security analysts to understand the nature of traf-fic present in a...

The GPU leverages SIMD efficiency when shading because it ras- terizes a triangle at a time, running the same shader on all of its fragments. Ray tracing sacrifices this shader coherence, and the result is that SIMD units often must run different shaders simul- taneously resulting in serialization. We study this problem and define a new measure cal...

ACM SIGGRAPH, the Association for Computing Machinery's Special Interest Group on Graphics, has sponsored an annual general conference since 1974. Over the past 35 years, the Technical Papers programme of the SIGGRAPH conference has become known throughout the world as the premier international forum for disseminating new scholarly work in computer...

Numerous techniques have been developed to perform advanced shading operations in real time. The real -time versions vary greatly from their original implementations due to the constraints of existing hardware and programming libraries. This paper introduces a grammar for articulating these modern real -time shading pipelines. We survey the existin...

This paper proposes novel methods for visualizing specifically the large power-law graphs that arise in sociology and the sciences. In such cases a large portion of edges can be shown to be less important and removed while preserving component connectedness and other features (e.g. cliques) to more clearly reveal the network's underlying connection...

Clip art is a simplified illustration form consisting of layered filled polygons or closed curves used to convey 3D shape information in a 2D vector graphics format. This paper focuses on the problem of direct conversion of smooth surfaces, ranging from the free-form shapes of art and design to the mathematical structures of geometry and topology,...

We describe a rendering system that converts a 3D meshed model into the stylized 2D filled-region vector-art commonly found in clip-art libraries. To properly define filled regions, we analyze and combine accurate but jagged face-normal contours with smooth but inaccurate interpolated vertex normal contours, and construct a new smooth shadow contou...

As graphics processors become powerful, ubiquitous and eas- ier to program, they have also become more amenable to general purpose high-performance computing, including the computationally expensive task of drawing large graphs. This paper describes a new parallel anal- ysis of the multipole method of graph drawing to support its ecient GPU impleme...

In this paper, we proposed a new approach for drawing rooted trees on circles. Previous approaches either draw entire tree on a single circle or draw too many circles that every node and its children are on a new circle. As a result, they only work well on limited kinds of trees. In contrary, our approach adaptively choose how many circles to use b...

Shape deformation is a common practice in digital image editing, but can unrealistically stretch or compress texture detail. We pro- pose an image editing system that decouples feature position from pixel color generation, by resynthesizing texture from the source image to preserve its detail and orientation around a new feature curve location. We...

Isochords is a visualization of music that aids in the classification of musical structure. The Isochords visualization highlights the con- sonant intervals between notes and common chords in music. It conveys information about interval quality, chord quality, and the chord progression synchronously during playback of digital music. Isochords offer...

We propose a video editing system that allows a user to apply a time-coherent texture to a surface depicted in the raw video from a single uncalibrated camera, including the surface texture mapping of a texture image and the surface texture synthesis from a texture swatch. Our system avoids the construction of a 3D shape model and instead uses the...

Resampling raw surface meshes is one of the most fundamental operations used by nearly all digital geometry processing systems. The vast majority of this work has focused on triangular remeshing, yet quadrilateral meshes are preferred for many surface PDE prob- lems, especially fluid dynamics, and are best suited for defining Catmull-Clark subdivis...

Using the GPU to accelerate ray tracing may seem like a natural decision due to the highly parallel nature of the problem. However, past attempts at a fully general GPU ray tracer have yielded poor performance compared to optimized CPU ray tracers. In this paper we instead focus on an algorithm for quick intersection of a single mesh on the GPU. Th...

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 per...

Dynamic surfaces arise in many applications, such as free surfaces in multiphase flows and moving interfaces in fluid-solid interactions. In many applications, an explicit surface triangulation is used to track the dynamic surfaces, posing significant challenges in adapting their meshes, especially if large curvatures and sharp features may dynamic...

An abstract is not available.

We present a non-photorealistic rendering approach to capture and convey shape features of real-world scenes. We use a camera with multiple flashes that are strategically positioned to cast shadows along depth discontinuities in the scene. The projective-geometric ...

Particle systems are an effective tool for visualizing information in a variety of contexts. This paper focuses on the use of surface-constrained particles to visualize information about the surface. We have designed a particle system programming framework consisting of behaviors, attributes and shaders that allows users to rapidly create, debug, a...

Material replacement has wide application throughout the entertainment industry, particularly for post-production make-up application or wardrobe adjustment. More generally, any low-cost mock-up object can be processed to have the appearance of expensive, high-quality materials. We demonstrate a new system that allows fast, intuitive material repla...

Point-based representations are becoming increasingly common in computer graphics, especially for visualizing data sets where the number of points is large relative to the number of pixels involved in their display. When dealing with sparse point sets, however, many traditional rendering algorithms for point data perform poorly, either by generatin...

Recently, point set surfaces has been the focus of a large number of research efforts. Several different methods have been proposed to define surfaces from points and have been used in a variety of applications. However, so far little is know about the mathematical properties of the resulting surface. A central assumption for most algorithms is tha...

Point-based representations are becoming increasingly common in computer graphics, especially for visualizing data sets where the number of points is large relative to the number of pixels involved in their display. When dealing with sparse point sets, however, many traditional rendering algorithms for point data perform poorly, either by generatin...

Recently, point set surfaces has been the focus of a large number of research efforts. Several different methods have been proposed to define surfaces from points and have been used in a variety of applications. However, so far little is know about the mathematical properties of the resulting surface. A central assumption for most algorithms is tha...

Particle systems are an effective tool for visualizing information in a variety of contexts. This paper focuses on the use of surface-constrained particles to visualize information about the surface. We have designed a particle system programming framework consisting of behaviors, attributes and shaders that allows users to rapidly create, debug, a...

Resampling raw surface meshes is one of the most fundamental operations used by nearly all digital geometry processing systems. The vast majority of work in the past has focused on triangular remeshing; the equally important problem of resampling surfaces with quadrilaterals has remained largely unaddressed. Despite the relative lack of attention,...

We present a novel algorithm for the rendering of hard shadows cast by a point light source. The well-known Z-pass method for rasterizing shadow volumes is not always correct. Our algorithm, which we call ZP+, elegantly corrects Z-pass defects. ZP+ takes advantage of triangle strips and fast culling capabilities of graphics hardware not available t...

Real-time procedural shading was once seen as a distant dream. When the first version of this course was offered four years ago, real-time shading was possible, but only with one-of-a-kind hardware or by combining the effects of tens to hundreds of rendering passes. Today, almost every new computer comes with graphics hardware capable of interactiv...

Surface painting is a technique that allows a user to paint a texture directly onto a surface, usually with a texture atlas: a 1:1 mapping between the surface and its texture image. Many good automatic texture atlas generation methods exist that evenly distribute texture samples across a surface based on its area and/or curvature, and some are even...

Modern techniques for interrogating the topology (e.g. genus) of a single meshed surface find handles via a breadth-first search for cycles that do not separate the mesh into two disjoint components. Morse theory can find handles with a simple search for the minima, maxima and saddles of a real function evaluated at the vertices. Bad choices for th...

We combine existing techniques for shape-from-shading and texture synthesis to create a new tool for texturing objects in photographs. Our approach clusters pixels with similar recovered normals into patches on which texture is synthesized. Distorting the texture based on the recovered normals creates the illusion that the texture adheres to the un...

We combine existing techniques for shape-from-shading and texture synthesis to create a new tool for texturing objects in photographs. Our approach clusters pixels with similar recovered normals into patches on which texture is synthesized. Distorting the texture based on the recovered normals creates the illusion that the texture adheres to the un...

Numerous mesh algorithms such as parametrization, radiosity, and collision detection require the decomposition of meshes into a series of clusters. In this paper we present two novel approaches for maintaining mesh clusterings on dynamically deforming meshes. The first approach maintains a complete face cluster tree hierarchy using a randomized dat...

We present a framework for translating procedural pro- ductionrules, suchasparametricL-Systemsbasedonscene graphs instead of turtle graphics, into a form that can iter- atively grow geometry completely on graphics hardware. The formulation is extended to handle context-sensitive, conditional and non-deterministic rules. We also examine and enhance...

This paper describes a technology for manipulating the shape of an implicitly modeled surface so that it follows a geometric flow. The proposed technology is a generalization of the method of level sets, which specifies how to manipulate the isosurfaces of greyscale functions, sampled on discrete grids. The proposed formulation projects the geometr...

Iterative clustering algorithms based on Lloyds algorithm (often referred to as the k-means al- gorithm) have been used in a wide variety of ar- eas, including graphics, computer vision, signal processing, compression, and computational ge- ometry. We describe a method for accelerating many variants of iterative clustering by using programmable gra...

This chapter focuses on procedural methods that generate new graphical objects by synthesizing geometry. These methods are designed to model the intricate detail found in natural shapes like plants. Procedural geometry synthesis creates an entirely new object by generating its geometry from nothing. The ideas of procedural geometry synthesis extend...

Assisted by recent advances in programmable graphics hardware, fast rasterization-based techniques have made significant progress in photorealistic rendering, but still only render a subset of the effects possible with ray tracing. We are closing this gap with the implementation of ray-triangle intersection as a pixel shader on existing hardware. T...

We compress storage and accelerate performance of precomputed radiance transfer (PRT), which captures the way an object shadows, scatters, and reflects light. PRT records over many surface points a transfer matrix. At run-time, this matrix transforms a vector of spherical harmonic coefficients representing distant, low-frequency source lighting int...

Recent advances in the speed and programmability of consumer level graphics hardware has sparked a flurry of research that goes beyond the realm of image synthesis and computer graphics. We examine the use of the GPU (graphics processing unit) as a tool for scientific computing, by analyzing techniques for performing large matrix multiplies in GPU...

Each tree is unique because of the physical environment it experiences over the course of its life. Environmental factors shape a tree, within the bounds of its genotype. Only by modeling the environment influences can we create realistic models of trees. Our effort is motivated by a desire to construct a predictive tool that can be used by both th...

This paper describes an interactive modeling method which allows a user to directly manipulate a fractal object defined by a recurrent iterated function system (RIFS). The method allows the user to nail points on the attractor to their current position, and drag other points to a desired position. The attractor changes shape to accomodate the new l...

We capitalize on recent advances in modern programmable graphics hardware, originally designed to support advanced local illumination models for shading, to instead perform two different kinds of global illumination models for light transport. We first use the new floating-point texture map formats to find matrix radiosity solutions for light trans...

We present an algorithm to construct a tight bounding polyhedron for a recursive procedural model. We first use an iterated function system (IFS) to represent the extent of the procedural model. Then we present an algorithm that expresses the IFS-bounding problem as a set of linear convex optimization. As such, our algorithm is guaranteed to find t...

Modern techniques for interrogating the topology (e.g. genus) of a single meshed surface find handles via a breadth-first search for cycles that do not separate the mesh into two disjoint components. Morse theory can find handles with a simple search for the minima, maxima and saddles of a real function evaluated at the vertices. Bad choices for th...

The third edition of this classic tutorial and reference on procedural texturing and modeling is thoroughly updated to meet the needs of today's 3D graphics professionals and students. New for this edition are chapters devoted to real-time issues, cellular texturing, geometric instancing, hardware acceleration, futuristic environments, and virtual...

Surface texturing aids the visualization of polygonal meshes by providing additional surface orientation cues and feature annotations. Such texturing is usually implemented via texture mapping, which is easier and more effective when the distortion of the mapping from the surface to the texture map is kept small. We have previously shown that disto...

Surface texturing aids the visualization of polygonal meshes by providing additional surface orientation cues and feature annotations. Such texturing is usually implemented via texture mapping, which is easier and more effective when the distortion of the mapping from the surface to the texture map is kept small.

This book covers real-time shading systems, their design and how they work. Procedural shading, long valued for off-line rendering and production animation is now possible on interactive graphics hardware. These developments are important for areas such as game development, product design, and scientific visualization, among others. The authors inc...

this paper is a new multiresolution texture atlas. It distributes all available texture samples in a nearly uniform distribution. This multiresolution texture atlas is the first of its kind to fully support MIP-mapped minification antialiasing and linear magnification filtering

Shortly after its introduction in 1985, procedural solid texturing became a must-have tool in the production-quality graphics of the motion-picture industry. Now, over fifteen years later, we are finally able to provide this feature for the real-time consumer graphics used in videogames and virtual environments. A texture atlas is used to create a...

In 1994, Witkin and Heckbert developed a method for interactively modeling implicit surfaces by simultaneously constaining a particle system to lie on an implicit surface and vice-versa. This interface was demonstrated to be effective and easy to use on example models containing a few blobby spheres and cylinders. This system becomes much more diff...

In 1994, Witkin and Heckbert developed a method for interactively modeling implicit surfaces by simultaneously constraining a particle system to lie on an implicit surface and vice-versa. This interface was demonstrated to be effective and easy to use on example models containing a few blobby spheres and cylinders. This system becomes much more dif...

Complex virtual environments can be simulated with physical or procedural motion. Physical motion is more realistic, but requires the integration of an ordinary differential equation from an initial state. Procedural motion has the advantage of being randomly accessible, though it is not physically based. We combine these techniques into a multires...