Computer graphics processing and selective visual display system – Computer graphics processing – Adjusting level of detail
Reexamination Certificate
1999-06-10
2004-04-06
Zimmerman, Mark (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Adjusting level of detail
C345S426000, C345S420000, C345S960000, C700S098000, C700S182000
Reexamination Certificate
active
06717579
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to computer-aided design (CAD), manufacturing (CAM) and engineering (CAE), and product data management (PDM II) systems and to a system and method for controlling the shape of reflection lines on the surface of an object in such CAD, CAM, CAE or PDM II systems. More particularly, the present invention provides for direct control of the reflection line and the modification of the shape of an object to correspond to a desired reflection line on the surface of the object.
BACKGROUND OF THE INVENTION
CAD systems are widely used for many types of design and manufacturing applications. Certain of these applications can be very costly in terms of user interaction time. One such interaction intensive application is object or surface design and modification.
In the computer-aided design and manufacturing of many end products, particularly those which are intended for the consumer market, the external appearance of the product plays a major role. The car industry provides a good example of this well-known fact. One significant aspect of the external appearance of the product is the way in which its surface reflects the light in the room where the product is presented to prospective buyers. This can be a car dealer showroom where neon tubes provide most of the light in the room and the prospective buyers see the reflection of the neon light as reflection lines on the external surface of the cars. It has been shown that smooth reflection lines tend to leave the consumer with a better impression of the product than erratic or misshapen reflection lines. This is why the design stylists in many consumer product manufacturing companies spend a lot of time trying to ensure that the end product will exhibit smooth reflection lines when presented in a showroom. They need to do that at the design stage, of course, before the product goes into production. It is therefore important for a CAD/CAM/CAE/PDM II application to offer design stylists the opportunity to control to the greatest extent possible the way the surface of the designed product will reflect light.
In the currently available systems, the surface of the object being designed is displayed to the user with a simulation of the reflection of a light source, say an elongated neon light source, system allows the user to alter the shape of the surface by means of free-form surface shape design techniques. Then the new reflection line is shown to the user and the process is repeated until the user is reasonably satisfied with what appears on the computer. In this process the user has no direct control over the reflection line: for the software functionalities the reflection line is only a “by-product” of the shape of the surface, whereas in many cases it is the ultimate goal of the user. This is a long and tedious trial-and-error process. There is a need for a system which would allow the user to define up front the reflection line the surface should preferably exhibit and which would then reshape the surface to attain or approximate this kind of reflection line.
A method for surface design and modification is described in an article titled Energy-Based Models for Free-Form Surface Shape Design, by George Celniker and David Gossard, ASME Design Automation Conference, February 1989, and in an article titled Linear Constraints for Deformable B-Spline Surfaces, by George Celniker and Will Welch, Association for Computing Machinery, 165-70, 1992 (Celniker et al.). In these articles a system is described which provides for the modification of the shape of a deformable surface. The system applies constraints defined by the user to the entire surface while attempting to reach an equilibrium. All changes to a surface reflect a minimization of a global energy function of the surface. Additionally, all curves are constrained by requiring an equilibrium which fixes each point and the shape of the entire curve. When using such a system for arriving at a desired (subjective) degree of smoothness for a surface, a user will often have to modify several times one or more constraints, which causes the system to go through several iterations in each of which the surface must be recalculated and displayed to the user, until the user finds the result acceptable. Celniker's constraint based model attempts to generate a smooth shape within the constraints imposed by the user, but does not address the issue of direct control of reflection lines or indirect control of the surface of an object through the use of its reflection lines.
Two different methods for surface modification are described in an article titled Correction of Local Surface Irregularities Using Reflection Lines, by Reinhold Klass, Computer Aided Design, Vol. 12, No. 2, March 1980, pp. 73-77, and in an article titled Smoothing Surfaces Using Reflection Lines for Families of Splines, by E. Kaufmann and R. Klass, Computer Aided Design, Vol. 20, No. 6, July/August 1988, pp. 312-16. These articles both describe methods for modifying a surface using reflection lines. Neither method provides for any surface constraints besides for the reflection line. These methods differ from Celniker et al. in that neither is based on a constraint based energy minimization model to guarantee global control of the surface, and no provision exists for introducing such a model. The lack of constraints other than the reflection line means that it is not possible to guarantee that the surface will not move at its boundaries. These methods demand large amounts of processing, and memory by requiring numerous calculations and reiterations to arrive at the desired reflection lines. Additionally, several user interaction may be necessary to insure that the surface shape provides the desired characteristics.
A further method for surface modification is described in an article titled Direct Highlight Line Modification on NURBS Surfaces, by Chen et al., Computer Aided Geometric Design 14 (1997) 583-601. This article describes a method for modifying a surface using highlight lines. The highlight lines differ from reflection lines in that they are viewer independent, i.e., not based on any viewer perspective, and are not subject to change based on a viewer's perspective. Thus, highlight lines are simpler to implement than reflection lines, but do not provide a realistic model for surface design or modification.
The various methods described in the literature for object modification using CAD systems are limited since they do not provide for object modification based on reflection line control while providing for constraints on the object being modified, and in consequence require time consuming user interaction to arrive at the desired result.
SUMMARY OF THE INVENTION
The present invention solves these problems and provides an apparatus and method for modifying the shape of an object, for example, a surface, by using reflection lines, while at the same time maintaining certain constraints on the object being modified. By using reflection lines an object may be modified based on a realistic viewer perspective.
The present invention provides an apparatus and method for modifying the shape of an object, for example, a surface, by defining the shape and/or position of one or more lines along which a light source is reflected by the object (reflection line). Based upon a change, such as, for example, the position and/or shape, to one or more of the reflection lines, the system modifies the shape of the object to correspond to the new surface requirements as defined by one or more of the modified reflection lines, while maintaining the constraint on the object as predetermined by the system or user. The light source may be any type of light source, such as, for example, a linear neon or fluorescent light, or a curved neon or fluorescent light.
The apparatus according to the present invention utilizes a CAD system, and provides for control of the reflection line using a control device, for example, a cursor control device, such as a mouse, a roller ball, a pressure pad,
Bonner David L.
Deslandes Arnaud
Chance US LLP Clifford
Dassault Systemes
Mahon James V.
Sealey Lance W.
Zimmerman Mark
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