Point properties

Functions/Subroutines
logical pure function	mod_cg2_points::cg2_are_counterclockwise (p0, p1, p2)
	Return .true. if the points {p0, p1, p2} are defined in counterclockwise order. More...
logical pure function	mod_cg2_points::cg2_is_point_left_of_line (l0, l1, p)
	Return .true. if point p is on the left side of the line (l0, l1) More...
logical pure function	mod_cg2_points::cg2_is_point_left_of_or_on_line (l0, l1, p)
	Return .true. if point p is on the left side of the line (l0,l1) or on the line. More...
logical pure function	mod_cg2_points::cg2_are_points_collinear (p0, p1, p2)
	Return .true. if the points p0, p1 and p2 are collinear. More...
logical pure function	mod_cg2_points::cg2_is_point_on_segment (s0, s1, p)
	Return .true. if the point p is on the line segment [s0, s1]. More...
double precision pure function	mod_cg2_points::cg2_perp_product (p0, p1)
	Return the 2D cross product of two points. More...
double precision pure function	mod_cg2_points::cg2_triangle_double_area (p0, p1, p2)
	Return twice the signed area of the triangle {p0, p1, p2}. More...

Detailed Description

This module defines various functions to detect the relative position of many points from each other.

Attention

Modify these functions at your own risk. Many algorithms depend on the specific behaviour of these functions. They are designed to not generate false negative results. Note that false positive results may occur due to the finite representation of real numbers. Take that into consideration when writing new algorithms.

Function/Subroutine Documentation

cg2_are_counterclockwise()

logical pure function mod_cg2_points::cg2_are_counterclockwise	(	double precision, dimension(2), intent(in)	p0,
		double precision, dimension(2), intent(in)	p1,
		double precision, dimension(2), intent(in)	p2
	)

Parameters

[in]

p0,p1,p2

Any given points

cg2_are_points_collinear()

logical pure function mod_cg2_points::cg2_are_points_collinear	(	double precision, dimension(2), intent(in)	p0,
		double precision, dimension(2), intent(in)	p1,
		double precision, dimension(2), intent(in)	p2
	)

Parameters

[in]

p0,p1,p2

Any given point

cg2_is_point_left_of_line()

logical pure function mod_cg2_points::cg2_is_point_left_of_line	(	double precision, dimension(2), intent(in)	l0,
		double precision, dimension(2), intent(in)	l1,
		double precision, dimension(2), intent(in)	p
	)

Parameters

[in]	l0,l1	Two points defining a line
[in]	p	Any given point

cg2_is_point_left_of_or_on_line()

logical pure function mod_cg2_points::cg2_is_point_left_of_or_on_line	(	double precision, dimension(2), intent(in)	l0,
		double precision, dimension(2), intent(in)	l1,
		double precision, dimension(2), intent(in)	p
	)

Parameters

[in]	l0,l1	Two points defining a line
[in]	p	Any given point

cg2_is_point_on_segment()

logical pure function mod_cg2_points::cg2_is_point_on_segment	(	double precision, dimension(2), intent(in)	s0,
		double precision, dimension(2), intent(in)	s1,
		double precision, dimension(2), intent(in)	p
	)

Parameters

[in]	s0,s1	The two extreme points of a given line segment
[in]	p	Any given point

cg2_perp_product()

double precision pure function mod_cg2_points::cg2_perp_product	(	double precision, dimension(2), intent(in)	p0,
		double precision, dimension(2), intent(in)	p1
	)

Parameters

p0,p1

Any given points

cg2_triangle_double_area()

double precision pure function mod_cg2_points::cg2_triangle_double_area	(	double precision, dimension(2), intent(in)	p0,
		double precision, dimension(2), intent(in)	p1,
		double precision, dimension(2), intent(in)	p2
	)

Attention

The area of {p0, p1, p2} is of the opposite sign of the area of any non-circular permutation of these points.

Parameters

[in]

p0,p1,p2

The three ordered points defining a triangle