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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)
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)
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)
We present a new approach to interactive modeling of free-form surfaces. Instead of a fixed mesh of control points, the model presented to the user is that of an infinitely malleable surface, with no fixed controls. The user is free to apply control points and curves which are then available as handles for direct manipulation. The complexity of the(More)