intersection.c File Reference

#include <stdlib.h>
#include <math.h>
#include <stdio.h>
#include "utils_core.h"
#include "geometry.h"

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Enumerations
enum	{   p_on_a = 1 , q_on_a = 2 , p_on_b = 4 , q_on_b = 8 ,   circles_are_identical = 16 }
enum	{   no_intersection = 0 , a_between_cd = 1 , b_between_cd = 2 , c_between_ab = 4 ,   d_between_ab = 8 }

Functions
static int	gcxgc (double const norm_vector_a[3], double const norm_vector_b[3], double p[3], double q[3])
static int	loncxlatc (double const gc_norm_vector[3], double const z, double p[3], double q[3])
static int	gcxlatc (double const gc_norm_vector[3], double const z, double p[3], double q[3])
static int	loncxlonc (double const norm_vector_a[3], double const norm_vector_b[3], double p[3], double q[3])
static int	pxgc (double const vec[3], double const norm_vector[3], double p[3], double q[3])
static int	pxlatc (double const vec[3], double z, double p[3], double q[3])
static int	pxp (double const vec_a[3], double const vec_b[3], double p[3], double q[3])
int	yac_circle_intersect (struct yac_circle a, struct yac_circle b, double p[3], double q[3])
static int	vector_is_between (double const a[], double const b[], double const p[], double sq_len_diff_ab)
static int	vector_is_between_lat (double const a[], double const b[], double const p[])
static void	compute_edge_middle_point_vec (enum yac_edge_type edge_type, double const a[3], double const b[3], double middle[3])
static int	yac_identical_circles_vec (enum yac_edge_type edge_type, double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3], int intersection_type)
static int	yac_identical_gcxgc_vec (double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3])
static int	yac_check_pq_gcxgc (double const a[3], double const b[3], double const c[3], double const d[3], double const p[3], double const q[3])
static void	compute_norm_vector (double const a[3], double const b[3], double norm_vector[3])
static int	yac_gcxgc_vec (double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3])
static int	yac_latcxlatc_vec (double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3])
	compute the intersection point two circles of latitude
static void	compute_lon_norm_vector (double const a[3], double const b[3], double norm_vector[3])
static int	yac_loncxlonc_vec (double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3])
	compute the intersection point two circles of longitude
static int	yac_check_pq_gcxlatc (double const a[3], double const b[3], double const c[3], double const d[3], double const p[3], double const q[3])
static int	yac_loncxlatc_vec (double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3])
	compute the intersection point of a meridian and a parallel
static int	yac_gcxlatc_vec (double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3])
	compute the intersection of a great circle with the parallel
static int	yac_pxp_vec (double const a[3], double const b[3], double p[3], double q[3])
static int	yac_pxgc_vec (double const point[3], double const a[3], double const b[3], double p[3], double q[3])
static int	yac_pxlat_vec (double const point[3], double const a[3], double const b[3], double p[3], double q[3])
static int	adjust_ret_value (int ret_value)
int	yac_intersect_vec (enum yac_edge_type edge_type_a, double const a[3], double const b[3], enum yac_edge_type edge_type_b, double const c[3], double const d[3], double p[3], double q[3])
int	yac_point_on_edge (double p[3], double const a[3], double const b[3], enum yac_circle_type circle_type)

Variables
static double const	tol = 1.0e-12

Enumeration Type Documentation

anonymous enum

anonymous enum

Enumerator
p_on_a
q_on_a
p_on_b
q_on_b
circles_are_identical

Definition at line 15 of file intersection.c.

anonymous enum

anonymous enum

Enumerator
no_intersection
a_between_cd
b_between_cd
c_between_ab
d_between_ab

Definition at line 23 of file intersection.c.

Function Documentation

adjust_ret_value()

static int adjust_ret_value ( int ret_value )

inlinestatic

Definition at line 757 of file intersection.c.

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compute_edge_middle_point_vec()

static void compute_edge_middle_point_vec ( enum yac_edge_type edge_type, double const a[3], double const b[3], double middle[3] )

static

Definition at line 366 of file intersection.c.

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compute_lon_norm_vector()

static void compute_lon_norm_vector ( double const a[3], double const b[3], double norm_vector[3] )

static

Definition at line 572 of file intersection.c.

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compute_norm_vector()

static void compute_norm_vector ( double const a[3], double const b[3], double norm_vector[3] )

static

Definition at line 491 of file intersection.c.

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gcxgc()

static int gcxgc ( double const norm_vector_a[3], double const norm_vector_b[3], double p[3], double q[3] )

static

computes the intersection of two great circles

Parameters

[in]	norm_vector_a	norm vector of circle a
[in]	norm_vector_b	norm vector of circle b
[out]	p	first intersection point
[out]	q	second intersection point

Returns

-1 if the two circles are identical; 2 otherwise

Definition at line 39 of file intersection.c.

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gcxlatc()

static int gcxlatc ( double const gc_norm_vector[3], double const z, double p[3], double q[3] )

static

Definition at line 94 of file intersection.c.

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loncxlatc()

static int loncxlatc ( double const gc_norm_vector[3], double const z, double p[3], double q[3] )

static

Definition at line 71 of file intersection.c.

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loncxlonc()

static int loncxlonc ( double const norm_vector_a[3], double const norm_vector_b[3], double p[3], double q[3] )

static

Definition at line 194 of file intersection.c.

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pxgc()

static int pxgc ( double const vec[3], double const norm_vector[3], double p[3], double q[3] )

static

Definition at line 218 of file intersection.c.

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pxlatc()

static int pxlatc ( double const vec[3], double z, double p[3], double q[3] )

static

Definition at line 240 of file intersection.c.

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pxp()

static int pxp ( double const vec_a[3], double const vec_b[3], double p[3], double q[3] )

static

Definition at line 252 of file intersection.c.

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vector_is_between()

static int vector_is_between ( double const a[], double const b[], double const p[], double sq_len_diff_ab )

inlinestatic

determines whether vector p is between vectors a and b (it is assumed, that a, b, and p are in the same plane)

Definition at line 315 of file intersection.c.

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vector_is_between_lat()

static int vector_is_between_lat ( double const a[], double const b[], double const p[] )

static

Definition at line 332 of file intersection.c.

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yac_check_pq_gcxgc()

static int yac_check_pq_gcxgc ( double const a[3], double const b[3], double const c[3], double const d[3], double const p[3], double const q[3] )

static

Definition at line 477 of file intersection.c.

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yac_check_pq_gcxlatc()

static int yac_check_pq_gcxlatc ( double const a[3], double const b[3], double const c[3], double const d[3], double const p[3], double const q[3] )

static

Definition at line 618 of file intersection.c.

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yac_circle_intersect()

int yac_circle_intersect	(	struct yac_circle	a,
		struct yac_circle	b,
		double	p[3],
		double	q[3] )

Definition at line 266 of file intersection.c.

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yac_gcxgc_vec()

static int yac_gcxgc_vec ( double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3] )

static

computes the intersection points of two great circles
based on http://www.geoclub.de/viewtopic.php?f=54&t=29689

Parameters

[in]	a	first point of edge a the is on a great circle
[in]	b	second point of edge a the is on a great circle
[in]	c	first point of edge b the is on a great circle
[in]	d	second point of edge b the is on a great circle
[out]	p	intersection point
[out]	q	intersection point

Returns

0 if the intersection points are neither on edge a or b
-1 if an error occurred
1st bit will be set if p is on edge a
2nd bit will be set if q is on edge a
3rd bit will be set if p is on edge b
4th bit will be set if q is on edge b 5th bit will be set if both great circles are identically

Remarks

both edges need to have length of at least yac_angle_tol

Definition at line 524 of file intersection.c.

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yac_gcxlatc_vec()

static int yac_gcxlatc_vec ( double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3] )

static

compute the intersection of a great circle with the parallel

compute the intersection points of a great circle (defined by a and b) and a circle of latitude (defined by c and d) (both circles need to have a length of at least yac_angle_tol) if p and q are != NULL they contain the intersection points the return value is:

• 0 if the intersection points are neither between (a and b) or (c and d)
• -1 if the two circles do not intersect or an error occurred
• 1st bit will be set if p is between a and b
• 2nd bit will be set if q is between a and b
• 3rd bit will be set if p is between c and d
• 4th bit will be set if q is between c and d
• 5th bit will be set if both circles are identically

  Remarks

  if -1 is returned neither p or q is set

  if the two circles only have one intersection point, p and q will be identically, but only the p bits will be set

  both edges need to have length of at least yac_angle_tol

Definition at line 685 of file intersection.c.

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yac_identical_circles_vec()

static int yac_identical_circles_vec ( enum yac_edge_type edge_type, double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3], int intersection_type )

static

Definition at line 388 of file intersection.c.

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yac_identical_gcxgc_vec()

static int yac_identical_gcxgc_vec ( double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3] )

static

Definition at line 460 of file intersection.c.

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yac_intersect_vec()

int yac_intersect_vec	(	enum yac_edge_type	edge_type_a,
		double const	a[3],
		double const	b[3],
		enum yac_edge_type	edge_type_b,
		double const	c[3],
		double const	d[3],
		double	p[3],
		double	q[3] )

computes the intersection points of two edges

Parameters

[in]	edge_type_a	type of edge a
[in]	a	first point of edge a
[in]	b	second point of edge a
[in]	edge_type_b	type of edge b
[in]	c	first point of edge b
[in]	d	second point of edge b
[out]	p	first intersection point
[out]	q	second intersection point

Returns

0 if the intersection points are neither on edge a or b
-1 if the two circles do not intersect
1st bit will be set if p is on edge a
2nd bit will be set if q is on edge a
3rd bit will be set if p is on edge b
4th bit will be set if q is on edge b
5th bit will be set if both circles are identically

Remarks

if -1 is returned neither p or q is set

if the two circles only have one intersection point, p and q will be identically, but only the p bits will be set

Definition at line 763 of file intersection.c.

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yac_latcxlatc_vec()

static int yac_latcxlatc_vec ( double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3] )

static

compute the intersection point two circles of latitude

compute the intersection points of two circle of latitude if p and q are != NULL they contain the intersection points the return value is:

• 0 if the intersection points are neither between (a and b) or (c and d)
• -1 if an error occurred
• 1st bit will be set if p is between a and b
• 2nd bit will be set if q is between a and b
• 3rd bit will be set if p is between c and d
• 4th bit will be set if q is between c and d
• 5th bit will be set if both edges are on the same circle of latitude

  Remarks

  both edges need to have length of at least yac_angle_tol

Definition at line 556 of file intersection.c.

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yac_loncxlatc_vec()

static int yac_loncxlatc_vec ( double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3] )

static

compute the intersection point of a meridian and a parallel

compute the intersection points of a circle of longitude (defined by a and b) and a circle of latitude (defined by c and d) if p and q are != NULL they contain the intersection points the return value is:

• 0 if the intersection points are neither between (a and b) or (c and d)
• -1 if an error occurred
• 1st bit will be set if p is between a and b
• 2nd bit will be set if q is between a and b
• 3rd bit will be set if p is between c and d
• 4th bit will be set if q is between c and d

  Remarks

  both edges need to have length of at least yac_angle_tol

Definition at line 646 of file intersection.c.

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yac_loncxlonc_vec()

static int yac_loncxlonc_vec ( double const a[3], double const b[3], double const c[3], double const d[3], double p[3], double q[3] )

static

compute the intersection point two circles of longitude

compute the intersection points of two circle of longitude if p and q are != NULL they contain the intersection points the return value is:

• 0 if the intersection points are neither between (a and b) or (c and d)
• -1 if an error occurred
• 1st bit will be set if p is between a and b
• 2nd bit will be set if q is between a and b
• 3rd bit will be set if p is between c and d
• 4th bit will be set if q is between c and d
• 5th bit will be set if both edges are on the same circle of longitude

  Remarks

  both edges need to have length of at least yac_angle_tol

Definition at line 599 of file intersection.c.

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yac_point_on_edge()

int yac_point_on_edge	(	double	p[3],
		double const	a[3],
		double const	b[3],
		enum yac_circle_type	circle_type )

Definition at line 860 of file intersection.c.

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yac_pxgc_vec()

static int yac_pxgc_vec ( double const point[3], double const a[3], double const b[3], double p[3], double q[3] )

static

Definition at line 716 of file intersection.c.

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yac_pxlat_vec()

static int yac_pxlat_vec ( double const point[3], double const a[3], double const b[3], double p[3], double q[3] )

static

Definition at line 740 of file intersection.c.

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yac_pxp_vec()

static int yac_pxp_vec ( double const a[3], double const b[3], double p[3], double q[3] )

static

Definition at line 710 of file intersection.c.

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Variable Documentation

tol

double const tol = 1.0e-12

static

Definition at line 13 of file intersection.c.