Curves and surfaces modeling based on a cloud of points

Details Curves and surfaces modeling based on a cloud of points Curves and surfaces modeling based on a cloud of points

1997-12-24

2001-06-26

Teska, Kevin J. (Department: 2123)

Data processing: structural design, modeling, simulation, and em

Modeling by mathematical expression

C703S006000

Reexamination Certificate

active

06253164

ABSTRACT:

REFERENCE TO APPENDIX
This application includes a section of a user manual for Alias|Wavefront Studio™ Version 8.5 entitled “NURBS Modeling in Alias”. The copyright owner has no objection to paper reproduction of the appendix as it appears in this patent document, or in the official files of the U.S. Patent & Trademark Office, but grants no other license and reserves all other rights whatsoever. The entire appendix is hereby incorporated by reference.
BACKGROUND
This invention relates to computer modeling, and in particular, to the creation of geometric models from digitized data.
Advances in computer technology have made possible realistic and accurate three-dimensional (3D) computer models of real-world objects. Such capability provides a way to prototype and test new designs quickly and cost-effectively. One method of creating these 3D models is to generate them using software which creates polygon meshes or mathematical representations of objects. Users of 3D computer modeling technology, however, are increasingly finding that some objects are easier to build as physical parts, for example using a traditional sculpting process, rather than through software-based 3D modeling techniques. To complete the overall modeling process, a computer representation of these physical models is needed. This can be accomplished, among other ways, through the use of scanning technology.
With recent advances in scanning technology, the use of digitized data is becoming an important part of the geometry creation process for designers and animators. Physical models can be scanned using a scanning system, producing a database of 3D points which can then be processed in software to produce curves and surfaces representative of the physical objects. A typical scanning process results in several scans of an object, producing several thousand to several million 3D points. These scanning devices may generate dimensional data using contact as well as non-contact techniques. For instance, the surface of an object may be traced by a tracer disk, a stylus or a touch probe scanner. Alternatively, an optical beam such as a laser beam may be irradiated on the exterior contours of the object and imaged onto a position detector. Using these various techniques, the 3D shape measuring device can generate a complete spatial description of the object as a cloud, or set, of points.
However, since computers have finite storage and processing capacity, it is undesirable to model an object with an infinite number of coordinate points. Moreover, these points may not be edited or manipulated easily by tools which expect the object to be represented mathematically by curves or surfaces.
SUMMARY
The invention provides a computer-implemented method of curve and surface modeling. The method stores in a computer memory a cloud of points associated with an object and least-square fits one or more curves or surfaces to the cloud of points. The resulting curves or surfaces representative of the object are easier to describe mathematically and require less computer resources to process.
In one aspect, each curve which is to be projected onto the point cloud associated with the object is fitted to the point cloud using various curve fit methods and parameters selected by the user. The curve fit method may be based on spans between selected points on the object, or may be based on a predetermined tolerance range. The parameters may be interactively altered, and the curve fitting process may be iteratively performed by the user until the fit is optimal.
In another aspect, the surfaces representative of the object may be fitted. A number of surface fit methodologies may be applied, including a gridded fit method and a detailed fit method, to arrive at a projected curve which more closely represents the object. The projected curve is fit to the cloud of points in accordance with user-specified criteria. Additionally, a user may modify the specified criteria iteratively to provide a better fit of the curves and surfaces to the cloud of points.
In another aspect, an interface is provided for use with a computer-based system for curve and surface modeling of a target. The interface enables a user to alter one or more parameters interactively. The interface also allows an automatic refitting of the curves or surfaces to the cloud of points in response to user-specified parameters.
Advantages of the invention may include one or more of the following. A cloud of points can be converted into segments such as planes, lines, and other object “primitives.” As a result, the object surfaces are easier to describe mathematically and require less computer resources to process. A computer modeler need not individually model each surface and assemble the surface into a completed object. Rather, the modeler is required only to capture spatial information and the system will generate all surfaces automatically.
Other features and advantages will become apparent from the following description and from the claims.


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