Computer graphics processing and selective visual display system – Computer graphics processing – Graph generating
Reexamination Certificate
1998-07-02
2001-03-20
Nguyen, Phu K. (Department: 2772)
Computer graphics processing and selective visual display system
Computer graphics processing
Graph generating
Reexamination Certificate
active
06204860
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to using wires as curves that effect object or model deformation and, more particularly, to a system where wires, independent of the characteristics of the object, can be used to give definition to an object and shape its deformable features.
2. Description of the Related Art
The modeling and animation of deformable objects is an active area of research. Free-form deformations (FFDs) and its variants are popular and provide a high level of geometric control over the deformation. These approaches typically involve the definition and deformation of a lattice structure of control points. By deforming the space defined by the lattice any object within the space is also deformed. An object embedded within the lattice is deformed by defining a mapping from the object to the undeformed lattice. The point in space in the deformed lattice is the deformation imparted to the point. The user deals with a level of detail dictated by the density of the control lattice. While very useful for coarse-scale deformations of an object, this technique can be difficult to use for finer-scale deformations, since a very dense control lattice and customized control lattice shape may be required. To perform fine control the “resolution” of the lattice needs to approach that of the portion of an object that is to be deformed. Manipulating a dense control lattice is often harder than deforming the underlying geometry directly, and arbitrarily shaped lattices (other than a box shape) can be cumbersome to construct.
What is needed is a deformation mechanism that is easy to control.
Axial deformations provide a more compact representation in which a one-dimensional primitive such as a line segment or curve is used to define an implicit global deformation. Axial deformations also use the notion of a reference curve and a closest point computation. The axial deformation technique relates two Frenet frames attached at the closest point on the curve and the corresponding point on the reference curve. The deformation imparted to a point is a portion of a transformation from the reference curve's Frenet frame to the Frenet frame on the deformed curve. The proportion is based on an interpolation of the closest distance of the point to the reference curve between two cutoff radii. However, axial deformations cannot provide a coarse-scale representation of the object surface, or provide an easily manipulated deformation primitive that highlight and track the salient deformable features of the object. In axial deformations as well as lattice based deformations the underlying geometric model of the object needs to be apparent to the user separate and apart from the line segment or curve used to define the axial deformation primitive.
What is needed is a primitive that provides a coarse-scale representation of the object surface and a primitive that can be directly manipulated while highlighting and tracking the deformable features of the object and in which the underlying geometric model of the object need not be apparent to the user.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a modeling primitive based on a wire.
It is another object of the present invention to provide a deformation primitive that is independent of the complexity of the underlying object model.
It is also an object of the present invention to provide an additional primitive, called a holder or domain curve, that define or restricts the domain of deformation about an object of a wire.
It is a further object of the invention to provide for the integration of the deformations from multiple wires without causing aggregate artifacts.
It is an object of the present invention to allow surfaces to be stitched together seamlessly.
It is an additional object of the present invention to provide a system that allows surfaces to be easily wrinkled.
It is an object of the present invention to allow flexible skeletons to be animated efficiently.
The above objects can be attained by a system that defines a wire curve deformation primitive that includes a free-form curve associated with a surface of a model. The wire curve includes a region of influence about the free-form curve that defines what points on the object will be deformed. A scale factor determines the amplitude of scaling or point movement caused by the wire curve. A blending function of the wire curve defines the transition from deformed regions of the object to undeformed regions of the object.
The wire curve can have domain or holder curves associated therewith that define the domain of deformation about an object caused by one or more wires by holding the points of the object in place. The holder curve can hold or keep a deformed point from moving as well as hold or keep an undeformed point from moving. Locators associated with a wire curve are used to define different parameters values along the wire curve.
The process of deforming relevant parts of an object include preprocessing steps of determining which points will be influenced by the wire curve calculating an influence function for each point. As the curve is manipulated, the deformation stage processing includes scaling, rotating and translating the points to be deformed.
When multiple wires deform a particular region of an object, the deformations caused by the individual wires are determined. These deformations are algebraically combined with a bias weighting toward larger deformations.
REFERENCES:
patent: 5659625 (1997-08-01), Marquart
patent: 5687259 (1997-11-01), Linford
patent: 5850463 (1997-11-01), Horii
Alan H. Barr, “Superquadrics and Angle-Preserving Transformations”, IEEE, Jan. 1981, pp. 11-23.
John E. Chadwick et al., “Layered Construction for Deformable Animated Characters”, Computer Graphics, vol. 23, No. 3, Jul. 1989, pp. 243-252.
Jules Bloomenthal et al., “Interactive Techniques for Implicit Modeling”, AMC, 1990, pp. 109-116.
Ron MacCracken et al., “Free-Form Deformations With Lattices of Arbitrary Topology”, Computer Graphics Proceedings, 1996, pp. 181-188.
Thomas W. Sederberg et al., “Free-Form Deformation of Solid Geometric Models”, Dallas, vol. 20, No. 4, Aug. 1986, pp. 151-160.
Brian Wyvill et al., “Animating Soft Objects”, The Visual Computer, 1986, pp. 235-242.
Nguyen Phu K.
Silicon Graphics Inc.
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