Figure hidden-line processing method

Details Figure hidden-line processing method Figure hidden-line processing method

1989-05-24

1991-12-24

Evans, Arthur G.

Communications: electrical

Land vehicle alarms or indicators

Internal alarm or indicator responsive to a condition of the...

340729, G06K 100

Patent

active

050758764

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
This invention relates to a method of processing hidden lines of a figure. More particularly, the invention relates to a figure hidden-line processing method in a case where a plurality of figures are displayed in superimposed form as in a perspective diagram.
2. Background Art
In a design and drafting system (CAD/CAM system) using a computer, a perspective plan view or perspective sectional view of a designed structure is displayed on a display screen or drafted on paper to check the design of the structure FIG. 10 is a perspective sectional view of a mold, in which plates Pij, parts provided on the plates (mounting bolts BLi, eject pins EPi, guide pins GPi, lifter pins, etc ) and the perspective figures of the part holes are displayed in superimposed form
In a perspective view, as will be apparent from FIG. 10, figures (parts, plates, part holes, etc.) are displayed or drawn in mutually superimposed form. Consequently, since the plates and bolts as well as the bolts and pins, for example, are displayed or drafted overlapping each other, the drawing is difficult to read.
Accordingly, in order to make the drawing easier to read, the conventional practice is to perform figure hidden-line processing to conceal unnecessary lines.
However, since the conventional hidden-line processing remakes the figure elements such as the straight lines and circular arcs that constitute a figure and these figure elements cannot be restored once they are remade, the hidden-line processing requires considerable time and the original figure cannot be displayed (restored) after hidden-line processing.
Furthermore, with the conventional hidden-line processing, a figure and portion overlapping the figure are ascertained by the operator himself, who is required to designate these portions on a figure element-by-element basis. This is a laborious operation.


SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a hidden-line processing method through which processing time can be curtailed and restoration is possible, and wherein hidden-line processing can be performed upon automatically ascertaining all superimposed figures merely by designating the superimposed figures in figure units.
In the figure hidden-line processing of the present invention, one main figure on an upper side and at least one subordinate figure on a lower side are designated from among a plurality of figures displayed in superimposed form on a display screen. When this is done, a point of intersection at which a figure element of the main figure intersects each figure element constituting the subordinate figure is obtained. In case of intersection, the figure element of the subordinate figure is divided at the point of intersection to generate subordinate figure elements, and a subordinate figure element on an inner side of the main figure is provided with information indicating that this subordinate figure element is not to be displayed. When a starting point of the figure element of the subordinate figure resides on an inner side of the main figure in case of non-intersection, this figure element data is provided with information indicating that this figure element is not to be displayed. Hidden-line processing is performed by not displaying, on the display screen, figure elements having the information indicating non-display.
In the present invention, when display of the entirety of a subordinate figure is requested in a state where the subordinate figure is being displayed with some of its lines concealed owing to hidden-line processing, the entirety of the subordinate figure requested is displayed.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of CAD/CAM system for practicing the present invention;
FIG. 2 is a view for describing the principal portions of a menu table;
FIGS. 3(a), 3(b), 4(a) and 4(b) are views for describing the general features of hidden-line processing;
FIG. 5 is a flowchart of hidden-line processing;
FIGS. 6(a), 6(b), 7(a) and 7(b) are views for describi

REFERENCES:
patent: 4847789 (1989-07-01), Kelly et al.

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