Computer graphics processing and selective visual display system – Computer graphics processing – Graphic manipulation
Reexamination Certificate
2000-05-02
2003-08-19
Brier, Jeffery (Department: 2672)
Computer graphics processing and selective visual display system
Computer graphics processing
Graphic manipulation
C345S619000, C345S646000, C345S648000, C345S649000, C345S660000
Reexamination Certificate
active
06608631
ABSTRACT:
FIELD
The invention relates generally to computer graphics and animation and more particularly to techniques for deforming or warping graphical objects.
BACKGROUND
Warping or deforming (the terms are used interchangeably) graphical models is an important operation in many areas of computer graphics. Deformation of planar curves is a basic operation in 2-D cartoon animation as well as in digital publishing. Surface and solid warping find widespread application solid and geometric model manipulation as well as 3-D animation. Many significant industries such as portions the entertainment industry and the medical imaging industry rely heavily on suites of computer graphics tools that include warping techniques.
There are many computer-implemented wraping techniques known in the art. Indeed, the literature is heavily populated with niche solutions to seemingly separate sets of problems. There is a need for a warping technique that addresses the general problems encountered in warp design and provides a general solution framework flexible enough, not only for warp designers to rapidly develop new warps, but also for them to achieve warp results comparable to the existing niche solutions when desired. Such a general solution technique would facilitate the comparison of warps, make key aspects of warps easier for the warp designer to understand, and allow a warp designer to increase his or her efficiency by more readily integrating existing solutions for particular aspects of a warp. Ideally, such a general solution technique would not compromise on the warp designer's ability to achieve the same warp results as could be obtained with conventional solutions. Still further, it would be desirable for such a general solution technique to enable warp results unobtainable with conventional solutions. Also it would be desirable for such a general solution technique to modify existing warping techniques to add new functionality. Additionally it would be desirable for such a general solution technique to faciliate analysis of warps for ascertaining desirable mathematical properties.
One such exemplary conventional solution are free form deformations (“FFD”s). Typically FFDs are manipulated by editing of positions of control points in a uniform 3-D lattice imposed on a parallelepiped volume. While this technique yields some desirable mathematical properties, it is can often be highly restrictive to a warp designer. For instance, with conventional FFDs, it is not practicable to create a deformation with a rotation effect centered around a single control point. To achieve such an effect with a conventional FFD, a higher resolution control lattice must typically be used; however, this too is undesirable as it complicates the deformation interface over the model. Thus it would be desirable for a warping system to exist that allowed for more complex warping effects to be easily obtained in conjunction with creating results similar to FFD-type warps.
Another exemplary conventional solution are image warps such as those described by Beier and Neely's, Feature-based image metamorphosis,
Computer Graphics
(
SIGGRAPH
'92
Proceedings
) vol. 26, pages 35-42, July 1992. In Beier and Neely's disclosure, image warps are defined by line-segment features. When two (or more) line segments “squeeze” a portion of the image, the warped image may exhibit undesirable spatial buckling artifacts. These artifacts arise out of an assumption that the transformation for a line segment feature should not deform the image in a direction perpendicular to the line segment. For a single-segment, this assumption may not lead to undesirable effects, however for more complex warps, spatial buckling can arise. Accordingly it would be advantageous if a warping system were available that could eliminate spatial buckling in feature based image warps.
Still another exemplary conventional technique is the framework taught by Singh and Fume in Wires: A geometric deformation technique,
SIGGRAPH
'98
Conference Proceedings
, Pages 405-414. ACM SIGGRAPH, Addison Wesely, July 1998. Wires provides an interactive deformation framework for complex geometric models based on a metaphor to a sculptor's armature, i.e., controllable curves that deform the surface of an graphical object near the curve (a “wire”). While the Wires framework provides a useful geometric deformation technique, it also can create buckling and tearing artifacts when a given wire's reference curve is shaped so that a set of points is equidistant from different parts of the curve that specify competing deformations. Therefore it would be beneficial if a warping technique existed that could provide the functionality of Wires-type techniques but in a way which enabled buckling and tearing artifacts to be eliminated.
Frequently variations on a (typically complex) surface are desired. Direct manipulation of the surface itself may be too time consuming. There are a number of conventional multiresolution editing schemes that provide some capability for efficient surface variation. However the conventional methods do allow adequate flexibility (for instance they often restrict the relationship between the fine surface model, e.g., a vertex mesh, and the control model in terms of topology or mesh connectivity). While some conventional methods do allow control models of arbitrary topology, such methods may only approximate the edited control points (rather than being interpolating). However, interpolating warps frequently can provide a more intuitive user interface. Accordingly a need exists for an interpolating warp that may be used to conveniently deform a more complex surface of arbitrary topology.
Also, warp designers commonly desire to deform a first surface by mapping regions of the first surface to regions of a second surface. For instance, in computer animation, when the first surface is impacted by the second surface, the first surface may be stretched out of shape. Some physics-based systems that implement this behavior do exist, however such systems are frequently inadequate for production of exaggerated or fictional animation effects. Thus it would be helpful for a warping technique to exist that facilitated deformations of surface regions.
SUMMARY
In order to provide solutions to these and other objectives, one aspect of the present invention are methods for generating graphical warps or deformations through feature-based transformation of an undeformed model to create a deformed model. An illustrative method includes receiving the undeformed model and a set of feature specifications each of the set of feature specifications including a source feature, a target feature, and related deformation parameters. The set of feature specifications contains elements for controlling the deformation of the undeformed model. An additional part of this illustrative method includes receiving a set of transformations corresponding to the set of feature specifications and for mapping the source feature to the target feature in each of the set of feature specifications, and receiving a set of strength fields corresponding to the set of feature specifications and defined over the undeformed model for scaling the magnitude of each of the set of transformations, establishing a set of scaled transformations. The illustrative method also includes receiving a set of weighting fields corresponding to the set of feature specifications and defined over the undeformed model for determining the relative influence of the set of scaled transformations; computing a sum of the set of scaled transformations, weighted by the set of weighting fields, creating a deforming function for deforming the undeformed model to generate the deformed model; and returning the deformed model.
In a variation of the illustrative method, at least one of the set of feature specifications is continuous and has corresponding parameterized strength field, transformation, and weighting field. In this variation, the illustrative method also includes receiving a sampling function for disc
Arent Fox Kintner & Plotkin & Kahn, PLLC
Brier Jeffery
Chung Daniel J
Pixar Amination Studios
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