1. Field of the Invention
The present invention relates to a method of image processing and an image processing apparatus for generating a desired image by performing a trimming process for at least two different surfaces displayed on the screen of a display unit along the line of intersection of these surfaces, and to a image processing program for implementing these processes on a computer and a recording medium including the image processing program recorded therein.
2. Description of Background Art
A three-dimensional CAD system is used for designing the construction of automotive vehicles and motorcycles and the like.
For example, trimming processes such as combining two objects (materials) and adding a curved surface (fillet) to the combined portion to form a smooth structural shape, or removing a part of an angular portion of an object (material) and adding a curved surface (blend) to the removed portion to produce a natural chamfered surface are performed with a three-dimensional CAD system.
In such a case, for example, in the process of adding a fillet, the trimming process is proceeded for example by the steps of producing a fillet at the intersected portion between two surfaces (including flat surfaces and curved surfaces), subsequently cutting a curved line produced at the end of the fillet as a cutting curve for each surface, selecting a portion to be left as a necessary surface and removing unnecessary portion.
When the cutting curve does not reach the boundary portion (profile line) between the original surfaces, the cutting process cannot be performed on the original surfaces without modification. Therefore, in the related art, the cutting curve extends to the boundary portion between the original surfaces so that it can be cut in a natural shape (for example, see JP-A-8-106553).
However, in handling surface data as a practical matter, for example, even when two difference surfaces appear to be intersecting “in a general way” in broad perspective, there is a case in which they do not intersect “in a general way” when viewed microscopically. The term “in a general way” here means that two surfaces share a single line segment or curved line segment.
The conceivable cases in which two surfaces are not intersected “in a general way” may be the following two cases.
The whole part of the line segment or the curved line segment produced at the end portion of the fillet is not placed correctly on the original surface, and in fact, a line of intersection (a line segment or a curved line segment shared by both surfaces) does not exist.
The whole part of the line segment or the curved line segment produced at the end portion of the fillet is not placed correctly on the original surface, and in fact, it is cut in spots on the original surface and exists in a group of a plurality of line segments or of curved line segments.
In the case of (1) described above, a line of intersection does not exist in fact and thus the portion that is to be a basis for automatically generating a cutting curve does not exist. Therefore, redesigning (regeneration) of the surface on which the fillet is added is preferable.
On the other hand, in the case of (2), though a group of lines including a plurality of line segments or curved line segments may be quoted as a portion that should be a basis for automatically generating a cutting curve, since the method in the related art employs the process of drawing an extension from a line of intersection to the boundary portion on the original surface, it is an essential prerequisite that a single line of intersection is extracted. As a consequent, it cannot be applied to a group of lines including a plurality of line segments or curved line segments, and thus a cutting curve cannot be automatically generated based on the aforementioned group of lines.
Therefore, in the related art, as regards such a group of lines including a plurality of line segments or curved line segments, the operator is obliged to perform work to correct the connect between the line segments, between the curved line segments, or between the line segments and the curved line segments by the use of a coordinate input device such as a mouse or the like. Such correcting work requires a significant time period, and is troublesome because an individual has to make the aforementioned group of lines into a single line of intersection.