JPH05250455A - Graphic containment deciding system in graphic display device - Google Patents

Abstract

PURPOSE:To decide whether a point is contained in the inside of a graphic or not, in the graphic display device which does not have a triangle generator, and in which an FB(frame buffer) does not have a work layer. CONSTITUTION:A rectangular area in which a triangle ABC is inscribed is set, and whether a designated point P belongs to the inside of this triangle ABC or not is decided, based on a total value of angles made by segments AP, BP and CP. In the case the total value is '0' degree, the point P exists in the outside of the triangle ABC, and in the case the value is 360 degrees, the point exists in the inside. Accordingly, even in the case the device does not have a triangle generator, and a frame buffer does not have a work layer, whether a designated arbitrary point P belongs to the inside of a graphic of the triangle ABC, etc., or not can be decided, and a pick processing can be executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphic inclusion determination system in a graphic display device.

[0002]

2. Description of the Related Art Conventionally, a graphic display device has been used as a computer graphics terminal. Graphic display devices are usually CRTs
A frame buffer for storing graphic information in a coordinate system corresponding to the screen of the display is provided. FIG. 3 shows an example of the configuration of such a device.

The device shown in this figure includes a segment buffer (SB) 10 and a graphic processor (GPU).
12, a frame buffer (FB) 14, a video generator (VDG) 16 and a CRT 18. The SB 10 is, for example, a buffer that stores graphic information (segment data) related to a graphic created by a user together with various attribute values.
12 reads the graphic information from this SB 10 and returns to FB 14
Bit expand on. On the SB 10, the graphic information is stored in a logical coordinate system called the world coordinate system, and the coordinate system of the FB 14 is a physical coordinate system corresponding to the screen of the CRT 18. The GPU 12 performs coordinate conversion from the logical coordinate system to the physical coordinate system, and thereby the CRT 18
Display a figure on the screen. VDG16 is FB14
Generate a video signal based on the above data, CRT18
Supply to.

In such an apparatus, a graphic picking function is also known. A figure pick is a CRT
This is a process of designating any one of the figures displayed on the screen of 18 with a pick device such as a mouse. GPU
Reference numeral 12 transfers the graphic information related to the pick to, for example, the host computer, or performs necessary processing according to the command.

In order to execute the pick processing, it is necessary to judge whether or not the point designated by the device by the cursor is inside the figure. That is, a plurality of figures are usually displayed simultaneously on the screen of the CRT 18, and the user designates a point inside the figure to be picked by the pick device. Graphic display device
It is determined which of the figures displayed on the screen of the CRT 18 the designated point belongs to, and the pick target is determined.

[0006]

As described above, in order to perform the pick process, it is necessary to determine whether or not the point exists inside the figure (for example, a triangle). When performing such a determination, for example, as shown in FIG.
The one having a work layer is used as. That is, FB
As 14 layers, in addition to the R, G, and B layers for each color, a work layer is provided, a triangle is drawn on the work layer by a triangle generator, and the values written in the work layer make the points inside the triangle or the like. It is determined whether there is any (Japanese Patent Application No. 4-44697)
No.). However, such a method cannot be adopted when the FB 14 does not have a work layer or when the apparatus does not have a triangle generator.

The present invention has been made to solve the above problems, and it is a case where the FB does not have a work layer and the apparatus does not have a triangle generator. Also aims at making it possible to determine whether or not a point exists inside a figure such as a triangle.

[0008]

In order to achieve such an object, the figure inclusion judging method of the present invention finds the maximum and minimum values of the X and Y coordinates of the vertices of the figure to be displayed, and obtains these values. Set a rectangular area in which the figure is inscribed, and determine whether the specified point belongs to this rectangular area. If it is determined that the specified point belongs, a line segment connecting the point and each vertex of the figure is determined. It is characterized in that it is set, the angles at which these line segments intersect are summed, and whether or not the point belongs to the internal area of the figure is determined based on the total value.

Further, in the figure picking method of the present invention, the figure inclusion determining method of the present invention is executed in response to a pick command accompanied by cursor designation, and a figure which includes a point designated by the cursor among the displayed figures is selected. Characterized by picking.

[0010]

In the figure inclusion determination method of the present invention, first,
The maximum and minimum values of the x and y coordinates of the vertices of the displayed graphic (eg, triangle) are obtained. Obtaining such coordinate values makes it possible to set a rectangular area inscribed by the figure. After setting such a rectangular area, it is determined whether or not the point designated by the pick command or the like belongs to this rectangular area. Next, when it is determined to belong, a line segment connecting the point and each vertex of the figure is set.
Then, when the angles that intersect these line segments are summed,
The total value makes it possible to determine whether or not the point belongs to the internal area of the figure. For example, if the figure is a triangle, and if the specified point exists inside the figure, the total value of the angles formed by the three line segments is 360 degrees,
If it does not belong to the inside, it will be 0 degrees. Therefore, even if the FB does not have a work layer and the device does not have a triangle generator, it is possible to determine whether the specified point belongs to the internal region of the graphic.

Further, in the figure picking method of the present invention, the figure picking is executed by using this figure inclusion determining method. That is, by executing the figure inclusion determination method of the present invention in a pick command such as a cursor specification, it is possible to generally select a figure including a point specified by the cursor from a plurality of displayed pictures.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 show the principle of the figure inclusion determination method according to an embodiment of the present invention. The present invention is
As the device configuration, for example, the same configuration as that shown in FIG. 3 can be executed. Also, it is not necessary to use a triangle generator as the device and to have the work layer shown in FIG. The following operation is executed by the GPU 12, for example.

In the present embodiment, first, the maximum and minimum values of the x and y coordinates of the vertices of the figure (triangle) displayed on the screen are obtained. Next, the rectangular area inscribed by the triangle is set based on the coordinate values thus obtained.
In this rectangular area, the point specified by the minimum x-coordinate and the minimum y-coordinate of the obtained coordinate values is the lower left point, and the point specified by the maximum x coordinate and the maximum y coordinate is the upper right point. It is the area to be. If multiple triangles are displayed on the screen, each of these triangles is displayed as shown in FIG.
The rectangular area is set as shown in.

Further, it is determined for each rectangular area whether or not the point designated by the pick command or the like belongs to these rectangular areas. As a result of performing such a determination, when it is determined that the designated point P belongs to the rectangular area related to the triangle, the determination related to the angle is executed as shown in FIG. That is, when the designated point P exists outside the triangle ABC, the sum of the angles formed by the line segments AP, BP, and CP is 0 degrees (FIG. 2A), and when it exists inside the triangle. It becomes 360 degrees (FIG. 2B). Therefore, it is possible to determine whether or not the point P exists inside the triangle ABC by executing the determination based on this total value.

As described above, according to this embodiment, even when the FB 14 having no work layer is used and the apparatus does not have the triangle generator, the designated point exists inside the triangle. It can be determined whether or not to do. Therefore, the process of this embodiment is particularly effective for the process of picking an arbitrary one of the plurality of triangles displayed on the screen by designating the cursor.

Since the polygon can be divided into triangles, the present invention can be applied to the recognition of polygons in general.

[0018]

As described above, according to the present invention,
Since the line segment that connects the specified point and each vertex of the figure is set, and whether the point belongs to the internal area of the figure is determined based on the total value of the angles at which these line segments intersect, the device Even when the frame generator does not have a triangle generator and the work layer does not have a work layer, it is possible to easily determine whether or not a point exists inside the figure, and especially pick processing can be executed quickly. It becomes possible to do.

[Brief description of drawings]

FIG. 1 is a diagram showing setting of a rectangular area in a figure inclusion determination method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a judgment as to whether or not a triangle is inside the present embodiment, and FIG. 2A shows a case where a point is outside.
(B) is a figure which respectively shows the case where a point exists inside.

FIG. 3 is a diagram showing a general configuration of a graphic display device.

FIG. 4 is a diagram showing a configuration of a frame buffer (FB) having a work layer.

[Explanation of symbols]

 14 frame buffer (FB) ABC triangle P point

Claims (2)

[Claims] 1. In a graphic display device for displaying a figure such as a triangle on a screen by expanding the figure information in a frame buffer, the maximum and minimum values of the X and Y coordinates of the vertices of the figure to be displayed are obtained, and The rectangular area inscribed by the figure is set by the value of, and it is determined whether the specified point belongs to this rectangular area. If it is determined that the point belongs, the line connecting the point and each vertex of the figure. A figure inclusion determination method characterized by setting minutes, summing the angles at which these line segments intersect, and determining whether or not the point belongs to the internal area of the figure based on the total value. 2. The figure inclusion determination method according to claim 1 is executed in response to a pick instruction accompanied by cursor designation, and a figure including a point designated by the cursor is picked out of the displayed figures. The figure pick method to do.