Method for determining points within polygon using simplified intersection calculations on computer

Abstract

The invention relates to a method for judging points in a polygon by using simplified intersection calculation on a computer, which comprises the following steps of: reading vertex coordinates of thepolygon into a memory of the computer to generate a bounding box of the polygon, performing uniform grid division on the bounding box of the polygon, and generating a strip-shaped structure parallel to a coordinate axis in a grid unit; meanwhile, judging whether fragments, segmented by intersection points of the grid lines and the edges of the polygon, of the grid lines are located in / out of the polygon; for one test point, emitting a ray from the test point, and the ray is parallel to a coordinate axis parallel to the strip-shaped structure when the strip-shaped structure is generated; counting the number of polygonal edges intersected by the ray until the polygonal edges reach a non-ambiguous grid line segment; whether the test point is located in the polygon can be known according to the parity of the number of intersection times and the attribute that the grid line segment reached by the ray is located in / out of the polygon. According to the method, intersection calculation can begreatly simplified, the parallel processing capacity of a computer is efficiently utilized, and the calculation efficiency is greatly improved.

Description

technical field [0001] The invention belongs to the fields of computer algorithm, computer graphics, computational geometry and geographic information system processing, and specifically relates to a method for determining and calculating a point within a polygon, that is, for a point's spatial position, it is judged whether the position is located in a polygon method within a defined spatial region. Background technique [0002] The determination and calculation of a point within a polygon is a basic computing technology in computer graphics, computational geometry, and geographic information system processing. For a polygon, any test point must be judged whether the point is located within the polygon. There are many works in this area, among which the ray method and the method based on uniform mesh division are widely used. The ray method is to send a ray from the test point and count the number of times it intersects with the sides of the polygon. If the number of inte...

AI Technical Summary

Problems solved by technology

[0003] Although the combination of the ray method and the uniform grid method reduces the computational complexity to a minimum, the intersection operation of the basic test ray and the edge of the polygon still has more calculations such as multiplication and addition. For computer processors , the computational cost is relatively high

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