JP3808218B2 - Method for exchanging shape data between different CAD models - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for exchanging shape data between different types of CAD , for example, when exchanging shape data between three-dimensional CAD, and particularly relates to facilitating handling of a curved surface which is a rotating surface.
[0002]
[Prior art]
When exchanging shape data between CADs via a standard format such as IGES used when exchanging data between different types of CAD, if the reading side CAD cannot handle the rotation surface representation, the rotation surface is set in advance. It is converted into an expression such as NURBS. When converting this rotating surface, the original shape is converted as it is.
[0003]
[Problems to be solved by the invention]
If the original shape is converted as it is when the rotating surface is converted as described above, a closed NURBS curved surface 7 is formed as shown in FIG. Handling as a free-form surface may be difficult.
[0004]
The present invention provides a shape data exchange method between different types of CAD that can improve such disadvantages, avoid generating a curved free curved surface that is difficult to handle, and convert to a curved surface that is easy to handle by dividing or limiting the area. It is intended to provide.
[0005]
[Means for Solving the Problems]
According to the method for exchanging shape data between different types of CAD according to the present invention, when exchanging shape data between different types of CAD, the computer on the reading side CAD determines that the rotation surface to be converted is a trimmed surface obtained by cutting a part of the curved surface. If the rotation surface to be converted is a non-trim surface, the step is to check whether the rotation angle of the rotation surface is 91 degrees or more, and the rotation angle of the rotation surface is less than 91 degrees. in the case of the trim surface includes the step of converting into another representation by as data exchange format, if the untrimmed surface rotation angle is more than 91 degrees of rotation surface in split untrimmed surface every 90 degrees non And converting to another representation as a trimmed surface.
[0006]
According to the second shape data exchange method between different types of CAD according to the present invention, when the shape data is exchanged between different types of CAD, the reading CAD computer cuts a part of the curved surface of the rotation surface to be converted. Check if trimmed or non-trimmed surface, if the rotating surface to be converted is a trimmed surface, check if the trimmed surface's outer boundary is rectangular, and if the trimmed surface's outer boundary is rectangular, trim Check if the inner boundary exists on the surface, and if there is no inner boundary on the trimmed surface, the rotation surface of the rotation surface to be converted and the rotation surface of the generating curve are limited by the rectangular side that is the outer boundary. a step of the rotating surface of the new untrimmed surface, the steps of the rotation angle of the plane of rotation of the new untrimmed surface investigate whether 91 degrees or more, when the rotation angle of the rotating surface is less than 91 degrees A step of directly converting to another representation by a data exchange format, and a step of dividing into 90 degrees when the rotation angle of the rotation surface is 91 degrees or more, and converting to another representation. .
[0007]
According to the third method for exchanging shape data between different types of CAD according to the present invention, when the shape data is exchanged between different types of CAD, the reading CAD computer cuts a part of the curved surface of the rotation surface to be converted. Check if trimmed or non-trimmed surface, if the rotating surface to be converted is a trimmed surface, check if the trimmed surface's outer boundary is rectangular, and if the trimmed surface's outer boundary is rectangular, trim Check if there is an internal boundary on the face, and if there is an internal boundary on the trimmed face, create a bounding box by defining a boundary that includes all internal boundaries, and the generated bounding box a rectangular outer boundary to obtain one rectangular outer eight rectangles that do not contain internal boundaries including internal boundaries and, outside that does not include an internal border 8 Rectangle, processing the surface of revolution with limited rotation angle and mother curve surface of revolution to be converted in a rectangular side is the outer boundary as the plane of rotation of the untrimmed surface, inner rectangle is rotated with internal boundary A step of converting the corner and the generating curve into a trimmed surface by limiting the rectangular side which is an outer boundary .
[0008]
According to the fourth method for exchanging shape data between different types of CAD according to the present invention, when exchanging shape data between different types of CAD, the computer on the reading side CAD cuts a part of the curved surface of the rotating surface to be converted. Check if trimmed or non-trimmed surface, if the rotating surface to be converted is a trimmed surface, check if the trimmed surface's outer boundary is rectangular, and if the trimmed surface's outer boundary is not rectangular, and having the steps of: generating a bounding box from the boundary, and a step of limiting a rectangular sides of the resulting bounding box the rotation angle and mother curve surface of revolution to be converted.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
According to the shape data exchange method between different types of CAD according to the present invention, when the shape data is exchanged between different types of CAD, it is determined whether the rotation surface to be converted is a trim surface or a non-trim surface, and the rotation to be converted with the determination result. The shape data is converted into another expression after predetermined processing according to surface conditions. When this process is performed, if the rotation angle of the curved surface is 91 degrees or more, the non-trimmed surface is divided every 90 degrees and then converted into another expression. If the rotation surface to be converted is a trim surface, the outer boundary is rectangular, and the inner boundary does not exist, the curved surface that is the rotation surface has the same area as the original trimmed rotation surface using the trim information. Convert to a non-trimmed surface and then convert to another representation. Furthermore, if the rotation surface to be converted is a trim surface, the external boundary is rectangular, and there is an internal boundary, use the internal boundary information to convert it to a trim surface with a small internal boundary and a non-trimmed surface. Convert to the expression. In addition, when the rotation surface to be converted is a trim surface and the external boundary is not rectangular, the boundary is limited using the trim information and converted to another expression.
[0010]
【Example】
FIG. 1 is a flowchart showing the processing of one embodiment of the present invention. When exchanging shape data between different types of three-dimensional CAD systems, as shown in FIG. 1, first, it is checked whether the rotating surface to be converted is a trimmed surface or a non-trimmed surface obtained by cutting a part of the curved surface (step). S1). When the rotation surface to be converted is a non-trim surface, it is checked whether the rotation angle of the rotation surface is 91 degrees or more (step S5). When the rotation angle of the rotation surface is a non-trim surface of less than 91 degrees, it is directly converted into another expression by the data exchange format (step S6). Further, as shown in FIG. 2, in the case of the non-trimmed surface 1 whose rotation angle is 91 degrees or more, as shown in FIG. 3, the non-trimmed surface 11 obtained by dividing the non-trimmed surface 1 every 90 degrees. , 12 to other expressions (step S7). When this non-trimmed surface 1 is divided, if the remaining surface divided every 90 degrees is 1 degree or less, the remaining surface is not divided and is converted into another expression together with the previous surface. To do. Thus, by dividing the non-trim surface 1 whose rotation angle is 91 degrees or more into 90 degrees, the rotation surface formed of the non-trim surface 1 can be easily converted.
[0011]
When the rotation surface to be converted is a trim surface, it is checked whether the external boundary of the trim surface in the parameter expression is a rectangle (step S2). If the outer boundary of the trim surface is a rectangle, it is checked whether an inner boundary exists on the trim surface (step S3). If there is no internal boundary on the trim surface, the external boundary of the trim surface in the parameter expression is a rectangle, so the rotation surface with the rotation angle of the rotation surface and the generating curve limited by the rectangle side that is the outer boundary is the rotation surface. Its own natural boundary matches the external boundary of the parameter representation. The rotation surface of the rotation surface and the data on the generating curve are limited as a new non-trim rotation surface (step S4). Then, it is checked whether or not the rotation angle of the rotation surface is 91 degrees or more (step S5). If the rotation angle of the rotation surface is less than 91 degrees, it is directly converted into another expression by the data exchange format (step S6). If the rotation angle of the rotation surface is 91 degrees or more, the rotation surface is divided every 90 degrees and converted into another expression (step S7). In this way, when the outer boundary of the trimmed surface is a rectangle, the rotating surface is converted to a non-trimmed surface, so that it can be easily converted.
[0012]
In addition, when the outer boundary of the trim surface is a rectangle and there are inner boundaries 2 and 3 on the trim surface as shown in FIG. 4, as shown in FIG. A boundary line including boundaries 2 and 3 is defined to generate a bounding box (step S8). For example, nine rectangles 41 to 49 are obtained from the generated bounding box and the rectangle of the outer boundary as shown in FIG. Out of these nine rectangles 41 to 49, the outer eight rectangles 41 to 44 and 46 to 49 that do not include the inner boundaries 2 and 3 are non-trimmed rotation surfaces by restricting the rotation angle and the bus line with the sides of the rectangle. (Step S9). Further, the inner rectangle 45 including the inner boundaries 2 and 3 is limited by the rotation angle and the sides of the rectangle, so that the outer boundary is processed as a trim surface that matches the natural boundary (step S10).
[0013]
As shown in FIG. 6, when the outer boundary of the trim surface 5 is not rectangular, a bounding box 6 is generated from the outer boundary of the parameter expression as shown in FIG. 7 (step S11). Then, the range of the generating curved surface of the trimmed surface 5 is reduced by limiting the rotation angle and the generating line with the rectangular side of the bounding box 6 that generated the generating line (step S12). A trimmed surface with a reduced range of the generating surface is converted by a data exchange format. In this way, the trim surface can be easily converted.
[0014]
【The invention's effect】
As described above, when exchanging shape data between different types of CAD, the present invention determines whether the rotating surface to be converted is a trimmed surface or a non-trimmed surface. Since the rotation surface to be converted is divided according to the rotation angle of the curved surface that is the rotation surface and then converted into another representation, the curved surface can be easily handled and converted into another representation.
[0015]
If the rotation surface to be converted is a trim surface, the outer boundary is rectangular, and the inner boundary does not exist, the curved surface that is the rotation surface has the same area as the original trimmed rotation surface using the trim information. If the rotation surface to be converted is a trim surface, the outer boundary is rectangular, and there is an inner boundary, the non-trimmed surface and area are converted using the information on the inner boundary. After converting to a trim surface with a small inner boundary, convert to another representation, and if the rotation surface to be converted is a trim surface and the outer boundary is not rectangular, use the trim information to limit the boundary. Since it is converted to another representation, the rotation surface to be converted can be converted into a manageable curved surface and then converted to another representation, facilitating handling when exchanging shape data between different CAD models. it can.
[Brief description of the drawings]
FIG. 1 is a flowchart showing processing of an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a non-trimmed surface having a rotation angle of 91 degrees or more.
FIG. 3 is an explanatory view showing a divided non-trim surface.
FIG. 4 is an explanatory view showing a trim surface having an internal boundary.
FIG. 5 is an explanatory diagram showing a trimmed surface divided by a bounding box.
FIG. 6 is an explanatory view showing a trim surface whose external boundary is not rectangular.
FIG. 7 is an explanatory diagram showing a bounding box of a trim surface whose outer boundary is not rectangular.
FIG. 8 is an explanatory diagram showing a closed NURBS curved surface.
[Explanation of symbols]
1 Non-trimmed surface 2 and 3 Trim surface inner boundary 41 to 49 Rectangle 5 Trim surface whose outer boundary is not rectangular 6 Bounding box

Claims (4)

When exchanging shape data between different types of CAD, the reading-side CAD computer checks whether the rotation surface to be converted is a trimmed surface or a non-trimmed surface obtained by cutting a part of the curved surface;
If the rotating surface to be converted is a non-trimmed surface, the step of checking whether the rotation angle of the rotating surface is 91 degrees or more;
In the case of a non-trimmed surface whose rotation angle is less than 91 degrees, a step of directly converting to another representation by a data exchange format;
If the untrimmed surface rotation angle is more than 91 degrees of rotation surface, and converting the other represent untrimmed surface as untrimmed surface that is divided every 90 degrees,
A method for exchanging shape data between different CAD models. When exchanging shape data between different types of CAD, the reading-side CAD computer checks whether the rotation surface to be converted is a trimmed surface or a non-trimmed surface obtained by cutting a part of the curved surface;
When the rotating surface to be converted is a trimmed surface, checking whether the outer boundary of the trimmed surface is rectangular;
If the outer boundary of the trimmed face is rectangular, check if the trimmed face has an inner boundary;
If the trim surface does not have an internal boundary, the rotation surface of the rotation surface to be converted and the rotation surface of the generating curve limited by the side of the rectangle that is the external boundary is set as the rotation surface of the new non-trimmed surface;
Checking whether the rotation angle of the rotation surface of the new non-trimmed surface is 91 degrees or more;
When the rotation angle of the rotation surface is less than 91 degrees, the step of directly converting to another representation by the data exchange format;
When the rotation angle of the rotation surface is 91 degrees or more, the step of dividing every 90 degrees and converting to another expression;
A method for exchanging shape data between different CAD models. When exchanging shape data between different types of CAD, the reading-side CAD computer checks whether the rotation surface to be converted is a trimmed surface or a non-trimmed surface obtained by cutting a part of the curved surface;
When the rotating surface to be converted is a trimmed surface, checking whether the outer boundary of the trimmed surface is rectangular;
If the outer boundary of the trimmed face is rectangular, check if the trimmed face has an inner boundary;
If the trim surface has an internal boundary, defining a boundary line including all the internal boundaries and generating a bounding box;
The resulting bounding box and with a rectangular outer boundary obtain one rectangular outer eight rectangles that do not contain internal boundaries including internal boundaries, the eight outer containing no internal boundary rectangle of the rotating surface to be converted Processing a rotation surface in which a rotation angle and a generating curve are limited by a rectangular side that is an outer boundary as a rotation surface of a non-trimmed surface;
The inner rectangle including the inner boundary is converted to a trim surface by restricting the rotation angle and generating curve with the sides of the outer boundary rectangle ;
A method for exchanging shape data between different CAD models. When exchanging shape data between different types of CAD, the reading-side CAD computer checks whether the rotation surface to be converted is a trimmed surface or a non-trimmed surface obtained by cutting a part of the curved surface;
When the rotating surface to be converted is a trimmed surface, checking whether the outer boundary of the trimmed surface is rectangular;
Generating a bounding box from the outer boundary if the outer boundary of the trim surface is not rectangular;
A step of limiting a rectangular sides of the resulting bounding box the rotation angle and mother curve surface of revolution to be converted,
A method for exchanging shape data between different CAD models.

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