Method of generating solid-shell object

Details Method of generating solid-shell object Method of generating solid-shell object

1998-03-10

2001-05-08

Zimmerman, Mark (Department: 2671)

Computer graphics processing and selective visual display system

Computer graphics processing

Three-dimension

C345S440000

Reexamination Certificate

active

06229545

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to methods of generating a 3-dimensional solid-shell object having a shell of a uniform thickness or nonuniform thickness, and particularly relates to a method of generating a 3-dimensional solid-shell object having a shell of a uniform thickness or nonuniform thickness in a manner suitable for a CAD/CAM (Computer Aided Design, Computer Aided Manufacturing) device.
2. Description of the Related Art
FIGS. 1A through 1G
are illustrative drawings for explaining an example of a method which generates a 3-dimensional solid-shell object having a shell of a uniform thickness. In the figures, a designation number
11
refers to a solid object shown in
FIG. 1A
, and a designation number
11
a
of
FIG. 1G
indicates a solid-shell object having a shell of a uniform thickness obtained after a shelling operation. A displaced-surface model is denoted as
11
b
, as shown
FIG. 1F. A
surface subjected to the shelling operation is shown as
12
in FIG.
1
A. The solid object
11
in
FIG. 1A
is comprised of surfaces
12
through
17
. The surfaces
13
through
17
are displaced inward to generate displaced surfaces
13
a
through
17
a
shown in FIG.
1
B. After removing interfering portions of the displaced surfaces
13
a
through
17
a
, post-interference-removal displaced surfaces
13
b
through
17
b
are obtained as shown in FIG.
1
E. Unnecessary portions
13
c
and
14
c
of the displaced surfaces
13
a
and
14
a
, respectively, are also shown in FIG.
1
C and FIG.
1
D.
In the related art, the solid object (solid model)
11
shown in
FIG. 1A
has a certain interior portion thereof removed by a shelling operation, and this shelling operation is carried out from the surface
12
subjected to the shelling operation. Hereinafter, the surface
12
is referred to as a shelling-designated surface. In the related art, the shelling operation is performed through steps as follows so as to generate the uniform-thickness-shell solid object
11
a.
(1) The displaced-surface model
11
b
is generated.
The displaced-surface model
11
b
(
FIG. 1F
) is comprised of displaced surfaces, and is generated as follows.
(1-a) The displaced surfaces
13
a
through
17
a
, (
FIG. 1B
) are generated by displacing the surfaces
13
through
17
inwardly. Here, the surfaces
13
through
17
are all the surfaces of the solid object
11
except the shelling-designated surface
12
. The displacement S shown in
FIG. 1B
is the thickness of a subsequently resulting shell.
(1-b) Unnecessary portions of the displaced surfaces
13
a
through
17
a
are removed therefrom to obtain the post-interference-removal displaced surfaces
13
b
through
17
b
shown in FIG.
1
E. This process is referred to as an interference-removal process, and is performed as follows
(1-b-1) Each of the displaced surfaces
13
a
through
17
a
is divided into portions along lines when the displaced surfaces
13
a
through
17
a
interfere with each other along these lines.
The displaced surfaces
13
a
through
17
a
are obtained by inwardly displacing the surfaces
13
through
17
other than the shelling-designated surface
12
by the displacement S. In other words, the surfaces
13
through
17
are shifted toward a direction in which a back side of each surface faces. With regard to the displaced surfaces
13
a
and
14
a
, the back side and the front side are shown in FIG.
1
C.
(1-b-2) A check is made with respect to each of the portions of the displaced surfaces
13
a
through
17
a
as to whether these portions are necessary.
When a given one of the displaced surfaces
13
a
through
17
a
is divided into portions by other ones of the displaced surfaces
13
a
through
17
a
serving as dividing surfaces, portions positioned on the front side (outer side) of the dividing surfaces are considered unnecessary. In
FIG. 1C
, for example, the portions
13
c
and
14
c
are positioned on the front side of the dividing surfaces with regard to the displaced surfaces
13
a
and
14
a.
In this case, therefore, the portions
13
c
and
14
c
shown in
FIG. 1D
are regarded as unnecessary.
(1-b-3) The unnecessary portions identified above are removed.
(1-c) The displaced-surface model
11
b
(
FIG. 1F
) is created by connecting the post-interference-removal displaced surfaces
13
b
through
17
b
, which are obtained after the interference-removal process.
(2) A set operation is applied to the solid object
11
(
FIG. 1A
) and the displaced-surface model
11
b
(
FIG. 1F
) so as to perform subtraction.
In this manner, a subtraction set operation is performed with regard to the solid object
11
and the displaced-surface model
11
b
, so that the displaced-surface model
11
b
is taken out of the solid object
11
from the shelling-designated surface
12
. After the shelling operation, the uniform-thickness-shell solid object
11
a
is obtained.
In the related-art method described above, a set operation is performed with regard to the solid object
11
and the displaced-surface model
11
b
in addition to the interference-removal process performed during the generation of the displaced-surface model
11
b.
This results in a large number of interference computations, thereby generating a huge processing load.
The reason why the set operation requires a large number of computations is given as follows.
Data of a solid object is comprised of topology data and geometry data. The topology data describes relations of connections between vertices, edges, loops, faces, etc. The geometry data includes coordinates of vertices, curve data of edges, surface data of faces, etc. When a set operation is performed to effect a subtraction operation, an OR operation, an AND operation, etc., between two given cubic objects, for example, interference computations are necessary with regard to 6×6 combinations between 6 surfaces of one cube and 6 surfaces of the other cube. Since interference operations have to be performed between two given surfaces even if these two surfaces may turn out to be having no interference with each other, each of computations for 6×6 combinations must be carried out with the same diligence, thereby requiring large computation resources.
Such a set operation described above can be considered inefficient when viewed from a certain angle.
In the case of shelling operations, interference between the solid object
11
and the displaced-surface model
11
b
occurs only between the shelling-designated surface
12
and each of the displaced surfaces
13
a
through
17
a.
If interference computations regarding the shelling-designated surface are incorporated into the interference-removal process performed during the generation of the displaced-surface model, a more efficient process can be achieved.
Further, it is apparent that the same applies in the case of generation of a solid-shell object which has a shell of non-uniform thickness.
Accordingly, there is a need for a method of generating a solid-shell object which can be efficiently performed by incorporating interference computations regarding a shelling-designated surface into the interference-removal process performed during generation of a displaced-surface model.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a method which can satisfy the need described above.
It is another and more specific object of the present invention to provide a method of generating a solid-shell object which can be efficiently performed by incorporating interference computations regarding a shelling-designated surface into the interference-removal process performed during generation of a displaced-surface model.
In order to achieve the above objects according to the present invention, a method of generating a solid-shell object from a solid object having a shelling-designated surface and other surfaces includes the steps of inwardly displacing the other surfaces to generate displaced surfaces, dividing the shelling-designated surface and the displaced

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