JPH0223479A - Picture display method - Google Patents

Abstract

PURPOSE:To decrease the number of times of the longitudinal decision of a segment and to make faster picture displaying by composing a macro segment of the segments, which are included in the same polyhedron in each scanning line and connected to it. CONSTITUTION:The shape information and connecting information of plural polygons constituting the polyhedron are inputted, the coordinate values and luminance of the intersection between a rim constituting the polygon and a scanning line plane are obtained, and segment information is prepared 1. Next, macro information is prepared 2 from the connecting information and segment information of the polygon, longitudinal decision 3 is executed for the all macro segments included in the same scanning line, a section to be displayed on a picture out of the macro segments is obtained, based on a decision result and the luminance of the both edge points of the segment, luminance calculation 4 of each picture element on a drawing is executed, the plural polyhedrons in the three-dimensional space are hidden-surface-erased, and they are displayed on a picture.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image display method for displaying a plurality of polyhedra in space as a two-dimensional image.

(Prior art) When displaying a plurality of polyhedra on a screen as a shaded two-dimensional image by removing hidden surfaces for each scan line, as is done in computer graphics, first, each polyhedron is constructed. Convert the vertices of each polygon to the screen coordinate system. Then, the column address X, row address y, depth value 2, and brightness i on the screen of each vertex are determined.

Typically, the coordinate transformation is a viewpoint-based perspective transformation. Next, for each scan line, the intersection with the ridge lines forming the polygon is determined, and a segment is created. Then, a method called a scan line algorithm is used to determine the front and back of each segment, and the brightness of the section to be displayed on the screen of each segment is determined. Details of this scan line algorithm are described in Document 1: [Graphic processing engineering using computer displays], written by Fujio Yamaguchi, published by Nikkan Kogyo Shimbun, Chapter 5, Hidden Surface Elimination Problem.

(Problems to be Solved by the Invention) In conventional hidden surface removal in units of scan lines in image display, overlaps are checked between all segments, and overlapping segments are judged before and after each other. therefore,
The number of times to determine overlap increases on the order of the square of the number of segments, and when the figure becomes complex, the number of times to determine the front and rear of each segment becomes enormous, resulting in an increase in processing time.

A method of sorting segments is known to solve these problems. The details are described in document 1, for example. By sorting the segments, it is possible to reduce the number of times segment overlap is determined. Furthermore, it is possible to utilize the similarity between scan lines, and the number of times the segments are judged before and after each other can be reduced.

Therefore, processing time can be reduced. However, if a method using this sorting is used, the processing itself becomes extremely complicated, and there is a problem that the hardware scale will be enormous if realized.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image display method that can reduce the number of forward/backward determinations between segments through simple processing by combining several connected segments into a macro segment. .

(Means for Solving the Problems) The image display method of the present invention projects each polygon constituting the polyhedron onto the screen in order to display a plurality of polyhedra in a three-dimensional space on the screen. The coordinate values and brightness of both end points of the segment are determined as information indicating a segment defined as a line connecting the points on the polygon corresponding to the end points of each scan line on the screen when The connection information of the segments constituting the macro segment is obtained as information indicating a macro segment composed of connected segments contained in the same polyhedron in each scan line of Based on the coordinate values of both end points of the macro segments included in the same scan line, the front and back of each macro segment is determined, and the brightness of each pixel on the screen is determined based on this determination result and the brightness of both end points of the segment. Features.

(Function) An image display method for displaying a polyhedron according to the present invention will be described. In displaying an image by removing hidden surfaces for each scan line, a polyhedron is first expressed using shape information and connection information of a plurality of polygons constituting the polyhedron. Next, segment information is obtained from the polygon shape information. A segment is a line segment connecting points on a polygon corresponding to both end points of each scan line when each polygon is projected onto the screen. Segment information is the coordinate values of both end points of a segment and the brightness on the screen corresponding to the end points.

Next, macro segment information is obtained based on the polygon connection information. Macro segments are defined by polygonal lines made up of connected segments included in the same polyhedron within each scan line. Macro segment information is connection information of segments that constitute a macro segment.

Next, front/back judgment is performed between all macro segments included in the same scan line. Front/back determination is a process of determining the front/back of each macro segment with respect to the screen, thereby making it possible to determine the visible range of the macro segment for display on the screen. In processing, first, macro segments with overlap are selected. Then, a set of overlapping segments is selected from among the segments constituting each macro segment. Then, by performing forward/backward determination between the selected segments based on the coordinate values of both end points of each segment, the forward/backward relationship between the macro segments is determined, and the visible range is determined.

Then, the brightness of each pixel on the screen is determined based on this determination result and the brightness at both end points of the segment. With this method, it is possible to reduce the number of times of forward/backward determination between segments.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a flowchart showing the process flow of the present invention. The input is the shape information and connection information of each polygon constituting the polyhedron. The shape information of a polygon includes the coordinate values and brightness of the vertices constituting the polygon, and the arrangement of the vertices. However, it is assumed that these coordinate values have been transformed into a coordinate system based on the screen by perspective transformation based on the viewpoint. Furthermore, instead of perspective transformation, coordinate transformation may be performed by parallel projection or the like. Second
Figure (aXb) is an explanatory diagram showing an example of polygonal shape information. As shown in Figure 2(a), the coordinate values of the vertices are the vertex number 1 (i=1.2...) and the corresponding coordinate value (
xi, yi, zi). As shown in FIG. 2(b), each polygon has a polygon number j (j=1
．． 2. ) and the sequence of vertex numbers Pjk (k=1.2.
) and the brightness Ijk corresponding to each vertex k in each polygon j. Note that the vertex numbers in FIG. 2(b) are arranged in order from the left so that a polygon is constructed by connecting them clockwise.

The vertex number and brightness of each polygon are recorded as many times as there are vertices forming the polygon, such as three for a triangle and four for a quadrilateral. These shape information can indicate the shape of a polygon. Polygon connection information is information indicating which other polygons an edge line forming a certain polygon is connected to. FIG. 3 (aXb) is an explanatory diagram showing an example of polygonal connection information. As shown in FIG. 3(a), each polygon has a polygon number 1 (i = 1.2...) and a number sequence LEij (j = 1) of the ridge line forming the left side of the polygon.
．． 2. ) and the number sequence REij of the edges forming the right side of the polygon. Here, the left side of a polygon means that it is on the left side of the line connecting the vertex with the smallest and largest y-coordinate values among the vertices that make up the polygon, and the right side of the polygon also applies. The same is true. When the end point of the edge line with the smallest y-coordinate is taken as the starting point and the one with the largest y-coordinate is taken as the end point, the numbers of the ridge lines in FIG. 3(a) are arranged from the left in descending order of the y-coordinate of the starting point. Note that the number of edges on the left and right sides of each polygon is written in the upper and lower rows of each polygon. As shown in Figure 3(b), each ridgeline is
Edge number i, the starting point FPi, the ending point EPi, the polygon LPOLi connected to the left side, and the polygon R connected to the right side
It is indicated by POLi. These connection information can indicate connections between polygons.

First, in segment information creation 1 in FIG. 1, segment information is obtained from polygon shape information. FIG. 4 is an explanatory diagram showing the segments. 21.22.23 as shown in Figure 4
is a polygon, 11 contains a certain scan line and XZ
It is a scan line plane parallel to the plane. The segment is 31.32.33 at the intersection of scan line plane 11 and polygon 21.22.23. The segment information includes information indicating the polygon corresponding to the segment, the coordinate values of the end points of the segments, and the brightness at points corresponding to the end points on the screen. FIG. 5 is an explanatory diagram showing an example of segment information. As shown in Fig. 5, each segment consists of a segment number 1 (i=1゜22..), a polygon number Ti corresponding to the segment, and an X coordinate value LX of the left end of the segment.
i, 2 coordinate value LZi, luminance LIi, and right end X coordinate value R
It is represented by Xi, two coordinate values RZi, and luminance RIi. Segment information can be created by determining the coordinate values and brightness at the intersections between the edges of the polygon and the scan line plane. The details are described in document 1, for example.

Next, in macro segment information creation 2 in FIG. 1, macro segment information is obtained from polygon connection information and segment information. Define macro segments by polylines made up of connecting segments. For example, in FIG. 4, it is a polygonal line connecting segments 31, 32, and 33.

Let macro segment information be a sequence of segments that make up a macro segment. FIG. 6 is an explanatory diagram showing an example of macro segment information. As shown in FIG. 6, each macro segment has a macro segment number i (i = 1
．． 2. ...) and the X coordinate values LXi, RXi of the left end and right end of the macro segment, and each segment 5EGijθ = 1.2 . ...
) are shown by arranging them in descending order of the leftmost X coordinate value. Macro segment information can be constructed by finding adjacent segments one after another, such as finding edges at both ends of a polygon corresponding to one segment, and finding segments corresponding to polygons connected to the edges. Note that since the macro segment information is similar between one scan line and the next scan line, it is also possible to obtain the macro segment information at high speed by utilizing this similarity.

Next, in the front/back judgment 3 between macro segments shown in FIG. 1, front/back judgment is performed between all macro segments included in the same scan line. By determining the front and back, the visible range of the macro segment to be displayed on the screen is determined. For this reason, first, it is determined whether there is an overlap between macro segments based on the X coordinate values of both end points of the macro segments. When there is an overlap, the front and back judgments are made as follows.

However, here it is assumed that there is no intersection between macro segments.

1) Select one point a on the scan line from the overlapping section with two macro segments MSL MS2 2)
Segment S1 containing a from each of MSI and MS2
, select S2 3) Perform front/back judgment between Sl and S2, and select the preceding segment as S. 4) It is determined that a macro segment containing S is in front. Furthermore, between the two segments in 3) The preceding and following judgments can be made using various methods from the segment information. For example, the depth values z1 and z2 of Sl and S2 at the above a are obtained from the X coordinate values and 2 coordinate values of the end points of Sl and S2, respectively, and Zl
, 81, determining before and after S2 from the magnitude of z2.

Then, the section to be displayed on the screen within each macro segment is determined.

Next, in brightness calculation 4 for each pixel in FIG. 1, the brightness of the pixels included in the section of each macro segment to be displayed on the screen is calculated. FIG. 7 is an explanatory diagram showing how to display it. As shown in FIG. 7, first, the brightness of both end points 43 and 47 in the section 41 of the macro segment 42 to be displayed on the screen is determined. The method is to
, S2, and perform linear interpolation or the like from the X coordinate values and brightness of both end points of Sl and S2. The brightness of each pixel included in the section 41 to be displayed on the screen is then determined based on the X coordinate value and brightness at both end points 43.47 and the end points 44, 45, 46 of the segment included in the section 41 to be displayed on the screen. is obtained by linear interpolation.

In this way, by determining the brightness of each pixel included in the section to be displayed on the screen for all macro segments, hidden surfaces of a plurality of polyhedra in the three-dimensional space can be removed and displayed on the screen.

(Effects of the Invention) As described above, by using the image display method of the present invention, it is possible to reduce the number of front/rear judgments between segments when displaying a polyhedron in space, so that it is possible to reduce the number of front/rear judgments between segments. It is possible to display images faster and in a simpler way.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an embodiment of the present invention, and FIG. 2 (aXb
) is an explanatory diagram showing an example of polygon shape information, and Fig. 3 (a
Xb) is an explanatory diagram showing an example of polygon connection information, Fig. 4 is an explanatory diagram showing a segment, Fig. 5 is an explanatory diagram showing an example of segment information, and Fig. 6 is an explanatory diagram showing an example of macro segment information. 7 are explanatory diagrams showing a method of displaying macro segments. In the figure, 1... Segment information creation, 2... Macro segment information creation, 3... Front/back judgment between macro segments,
4... Brightness calculation of each pixel, 11... Scan line plane, 21.22.23... Polygon, 31.32.3
3... Segment, 41... Section, 43, 47...
- End point, 44.45.46... End point of the segment.

Claims (1)

[Claims] In order to display multiple polyhedra in three-dimensional space on the screen,
Information indicating a segment defined as a line segment connecting points on the polygon corresponding to both end points of each scan line on the screen when each polygon constituting the polyhedron is projected onto the screen. The coordinate values and brightness of both end points of the segment are determined as follows, and the macro segment is constructed as information indicating a macro segment composed of connected segments included in the same polyhedron within each scan line. Ask for segment connection information,
Based on the coordinate values of both end points of multiple segments included in the above-mentioned macro segment, judgment is made between macro segments included in the same scan line, and based on this judgment result and the brightness of both end points of the above-mentioned segments, the screen An image display method characterized by determining the brightness of each pixel.