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A snake is an energy-minimizing spline guided by external constraint forces and influenced by image forces that pull it toward features such as lines and edges. Snakes are active contour models: they lock onto nearby edges, localizing them accurately. Scale-space continuation can be used to enlarge the capture region surrounding a feature. Snakes provide a(More)
—The extrema in a signal and its first few derivatives provide a useful general-purpose qualitative description for many kinds of signals. A fundamental problem in computing such descriptions is scale: a derivative must be taken over some neighborhood, but there is seldom a principled basis for choosing its size. Scale-space filtering is a method that(More)
The bottleneck in most cloth simulation systems is that time steps must be small to avoid numerical instability. This paper describes a cloth simulation system that can stably take large time steps. The simulation system couples a new technique for enforcing constraints on individual cloth particles with an implicit integration method. The simulator models(More)
We present a new particle-based approach to sampling and controlling implicit surfaces. A simple constraint locks a set of particles onto a surface while the particles and the surface move. We use the constraint to make surfaces follow particles, and to make particles follow surfaces. We implement <i>control points</i> for direct manipulation by specifying(More)
Oriented patterns, such as those produced by propagation , accretion, <>r deformation, ore common in nature and therefore an important cl ass for visual analysis. Our approach to understanding such patterns is to decompose them into two parts: a flow field, describing the direction of anisotropy, and the residual pattern obtained by describing the i mage in(More)
Scale-space filtering constructs hierarchic symbolic signal descriptions by transforming the signal into a continuum of versions of the original signal convolved with a kernal containing a scale or bandwidth parameter. It is shown that the Gaussian probability density function is the only kernel in a broad class for which first-order maxima and minima,(More)
Spacetime constraints are a new method for creating character animation. The animator specifies <i>what</i> the character has to do, for instance, "jump from here to there, clearing a hurdle in between;" <i>how</i> the motion should be performed, for instance "don't waste energy," or "come down hard enough to splatter whatever you land on;" the character's(More)