Method and system for dynamically updating geometric models

Details Method and system for dynamically updating geometric models Method and system for dynamically updating geometric models

2000-01-12

2003-12-16

Picard, Leo (Department: 2125)

Data processing: generic control systems or specific application

Specific application, apparatus or process

Product assembly or manufacturing

Reexamination Certificate

active

06665569

ABSTRACT:

FIELD OF THE INVENTION
This application relates to computer-aided-design systems, and in particular, to methods and systems for providing dynamic links between a geometric model and the constituents of that geometric model.
BACKGROUND
A computer-aided design (CAD) system is a tool for creating geometric models on a computer system. These geometric models, which are typically representative of physical objects, are built by a designer using a series of commands that instruct the system to create geometric primitives, such as edges and vertices, and to operate on these geometric primitives using various procedures supplied with the CAD system. These operations result in the creation of geometric elements which can then be assembled, using additional procedures, into a geometric model.
A typical procedure supplied with a CAD system generates an output representative of a geometric structure on the basis of one or more input parameters in an input parameter list. For example, a procedure might accept a circle, an axis, and an angle as input parameters and create a solid by rotating the circle about the axis by the angle. Another procedure might accept a polygon and a length as input parameters and extrude that polygon to the extent specified by the length, thereby generating a prism having the polygon as its cross-section. Yet another procedure might accept, as input parameters, two intersecting faces and return a structure in which the intersection of the input faces is smoothed out into a curve. One or more of the input parameters passed to a procedure can itself be the output of another procedure. This ability to evaluate compositions of procedures enables the designer to build geometric models of complex physical objects by performing a sequence of operations on relatively simple constituent components.
To create a geometric model, a designer typically performs successive transformations on geometric primitives. For example, to generate the relatively simple prism shown in
FIG. 1
, a designer might define six edges
12
a-f
. The effect of this definition persists in time, thereby allowing the edges to be used as input parameters for subsequently called procedures. The designer would then apply an extrusion procedure to generate a prism
16
by extending the hexagon
12
formed by these six edges
12
a-f
along a principal axis
18
. For more complex geometric models, a lengthy chain of procedures is often required, with the output of one procedure serving as an input to the next procedure in the chain. An example of pseudo-code one might use to describe the construction of the geometric model in
FIG. 1
is shown in FIG.
5
.
FIG. 2
illustrates a prior art data structure
20
representative of a geometric model designated by a pointer to the output of a third procedure
22
. This third procedure
22
has a pointer to both a first geometric primitive
23
and the output of a second procedure
24
. As a result, the first geometric primitive
23
and the output of the second procedure
24
are input parameters in the input parameter list of the third procedure
22
. The second procedure
24
has a first pointer to the output of a first procedure
25
and a second pointer to a second geometric primitive
26
. As a result, the second geometric primitive
26
and the output of the first procedure
25
are input parameters in the input parameter list of the second procedure
24
. The first procedure
25
has three pointers: a first pointer directed to a third geometric primitive
27
, a second pointer directed to a fourth geometric primitive
28
, and a third pointer directed to a fifth geometric primitive
29
. Consequently, the input parameter list of the first procedure includes, as input parameters, the third, fourth, and fifth geometric primitives. Consequently, the input parameter list of the first procedure includes as input parameters, the third, fourth, and fifth geometric primitives.
In most cases, a design undergoes several iterations before completion. Each iteration can require revisions having ramifications that propagate throughout the geometric model. For example, with reference to
FIG. 1
, if the designer were to lengthen two edges
12
b
,
12
e
, the appearance of the entire prism
16
would have to be altered, as shown in FIG.
3
. Were this prism
16
to be an input parameter to a second procedure, the output of that second procedure would most likely have to be altered.
Examination of
FIG. 2
suggests that a change in, for example, the second geometric primitive
26
will be manifested in a change in the output of the second procedure
24
because the second procedure
24
has a pointer directed at the second geometric primitive
26
. The result of changing the second geometric primitive
26
will be manifested in a change in the output of the third procedure
27
because that procedure includes a pointer to the output of the second procedure
26
. As a result, the change in the second geometric primitive
26
is manifested in a change in the geometric model, which has a pointer directed to the output of the third procedure
27
.
It is thus known in the art to dynamically link the output of one procedure to the input of another procedure in such a way that the ramifications of a change in the dimensions of a geometric primitive propagate throughout the geometric model. This ability to dynamically update the geometric model is made possible by the fact that the constituent geometric primitives of a geometric model have unique tags, or identifiers, that are available to each procedure. Consequently, a procedure can accommodate changes in an input parameter by looking up the tag associated with that input parameter and obtaining the properties associated with the constituent element identified by that tag.
A more fundamental change to the geometric model poses significant problems in dynamically updating that model. For example, it is not possible to transform the prism in
FIG. 1
into the prism shown in
FIG. 4
by merely changing the dimensions or the orientation of existing edges. Instead, it is necessary to actually delete two edges
12
e
,
12
f
. Examination of the pseudo-code shown in
FIG. 5
suggests a lurking difficulty in deleting an edge. Since two of the edges
12
e
,
12
f
in the input parameter list of the extrude function will no longer exist, the extrude function will encounter an error. This disadvantage arises from the fact that in conventional methods of geometric modeling, even if the values of the parameters in the input parameter list are dynamically bound to the procedure, the input parameter list itself is statically bound to that procedure. Hence, although a procedure can be responsive to a change in the value of one of the input parameters in its input parameter list, it cannot readily respond to a change in the input parameter list itself.
In the context of the foregoing example, a change in the length of the edge
12
e
, as shown in
FIG. 3
, is merely a change in the value of an input parameter in an input parameter list. Such a change can readily be accommodated by known geometric modeling systems in which parameter values are dynamically bound to the procedure. However, the actual deletion of the edge
12
e
, as shown in
FIG. 4
, is a change in the input parameter list itself. Such a fundamental change cannot readily be accommodated by existing geometric modeling systems.
The difficulty associated with such a fundamental change in the geometric model is also apparent from FIG.
2
. For example, the outright deletion of the second geometric primitive
26
results in the second procedure
24
having a stray pointer with nothing to point to. Consequently, in order to avoid an error in the second procedure
24
, this stray pointer must also be deleted. Although this appears to be a relatively simple task in the simple example of
FIG. 2
, for a geometric model of even moderate complexity, there may be a large number of stray pointers, in which case the process of deleting stray pointers is a laborious one.
Conversely, if an additi

Affiliated with

Also associated with

Rating

Method and system for dynamically updating geometric models does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method and system for dynamically updating geometric models, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for dynamically updating geometric models will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3134317