GRASS GIS 8 Programmer's Manual
8.5.0dev(2024)-5719ba6fd5
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Vector library - intersection. More...
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <math.h>
#include <grass/vector.h>
#include <grass/glocale.h>
Go to the source code of this file.
Macros | |
#define | D ((ax2 - ax1) * (by1 - by2) - (ay2 - ay1) * (bx1 - bx2)) |
#define | D1 ((bx1 - ax1) * (by1 - by2) - (by1 - ay1) * (bx1 - bx2)) |
#define | D2 ((ax2 - ax1) * (by1 - ay1) - (ay2 - ay1) * (bx1 - ax1)) |
Functions | |
int | line_check_intersection (struct line_pnts *APoints, struct line_pnts *BPoints, int with_z) |
int | Vect_segment_intersection (double ax1, double ay1, double az1, double ax2, double ay2, double az2, double bx1, double by1, double bz1, double bx2, double by2, double bz2, double *x1, double *y1, double *z1, double *x2, double *y2, double *z2, int with_z) |
Check for intersect of 2 line segments. More... | |
int | Vect_line_intersection (struct line_pnts *APoints, struct line_pnts *BPoints, struct bound_box *ABox, struct bound_box *BBox, struct line_pnts ***ALines, struct line_pnts ***BLines, int *nalines, int *nblines, int with_z UNUSED) |
Intersect 2 lines. More... | |
int | Vect_line_check_intersection (struct line_pnts *APoints, struct line_pnts *BPoints, int with_z) |
Check if 2 lines intersect. More... | |
int | Vect_line_get_intersections (struct line_pnts *APoints, struct line_pnts *BPoints, struct line_pnts *IPoints, int with_z) |
Get 2 lines intersection points. More... | |
Vector library - intersection.
Higher level functions for reading/writing/manipulating vectors.
Some parts of code taken from grass50 v.spag/linecros.c
Based on the following:
(ax2-ax1)r1 - (bx2-bx1)r2 = ax2 - ax1 (ay2-ay1)r1 - (by2-by1)r2 = ay2 - ay1
Solving for r1 and r2, if r1 and r2 are between 0 and 1, then line segments (ax1,ay1)(ax2,ay2) and (bx1,by1)(bx2,by2) intersect.
Intersect 2 line segments.
Returns: 0 - do not intersect 1 - intersect at one point
\ / \ / \ / \/ \/ \/ /\ \ / \ \ 2 - partial overlap ( \/ ) ------ a ( distance < threshold ) ------ b ( ) 3 - a contains b ( /\ ) ---------- a ----------- a ---- b ----- b 4 - b contains a ---- a ----- a ---------- b ----------- b 5 - identical ---------- a ---------- b
Intersection points:
return point1 breaks: point2 breaks: distance1 on: distance2 on: 0 - - - - 1 a,b - a b 2 a b a b 3 a a a a 4 b b b b 5 - - - -
Sometimes (often) is important to get the same coordinates for a x b and b x a. To reach this, the segments a,b are 'sorted' at the beginning, so that for the same switched segments, results are identical. (reason is that double values are always rounded because of limited number of decimal places and for different order of coordinates, the results would be different)
(C) 2001-2009, 2022 by the GRASS Development Team
This program is free software under the GNU General Public License (>=v2). Read the file COPYING that comes with GRASS for details.
Definition in file vector/Vlib/intersect.c.
#define D ((ax2 - ax1) * (by1 - by2) - (ay2 - ay1) * (bx1 - bx2)) |
Definition at line 91 of file vector/Vlib/intersect.c.
#define D1 ((bx1 - ax1) * (by1 - by2) - (by1 - ay1) * (bx1 - bx2)) |
Definition at line 92 of file vector/Vlib/intersect.c.
#define D2 ((ax2 - ax1) * (by1 - ay1) - (ay2 - ay1) * (bx1 - ax1)) |
Definition at line 93 of file vector/Vlib/intersect.c.
Definition at line 1276 of file vector/Vlib/intersect.c.
References RTree_Rect::boundary, and G_malloc.
int Vect_line_check_intersection | ( | struct line_pnts * | APoints, |
struct line_pnts * | BPoints, | ||
int | with_z | ||
) |
Check if 2 lines intersect.
Points (Points->n_points == 1) are also supported.
Superseded by the faster Vect_line_check_intersection2() Kept as reference implementation
APoints | first input line |
BPoints | second input line |
with_z | 3D, not supported (only if one or both are points)! |
Definition at line 1466 of file vector/Vlib/intersect.c.
int Vect_line_get_intersections | ( | struct line_pnts * | APoints, |
struct line_pnts * | BPoints, | ||
struct line_pnts * | IPoints, | ||
int | with_z | ||
) |
Get 2 lines intersection points.
A wrapper around Vect_line_check_intersection() function.
Superseded by the faster Vect_line_get_intersections2() Kept as reference implementation
APoints | first input line | |
BPoints | second input line | |
[out] | IPoints | output with intersection points |
with_z | 3D, not supported (only if one or both are points)! |
Definition at line 1489 of file vector/Vlib/intersect.c.
int Vect_line_intersection | ( | struct line_pnts * | APoints, |
struct line_pnts * | BPoints, | ||
struct bound_box * | ABox, | ||
struct bound_box * | BBox, | ||
struct line_pnts *** | ALines, | ||
struct line_pnts *** | BLines, | ||
int * | nalines, | ||
int * | nblines, | ||
int with_z | UNUSED | ||
) |
Intersect 2 lines.
Creates array of new lines created from original A line, by intersection with B line. Points (Points->n_points == 1) are not supported.
Superseded by the faster Vect_line_intersection2() Kept as reference implementation
APoints | first input line | |
BPoints | second input line | |
[out] | ALines | array of new lines created from original A line |
[out] | BLines | array of new lines created from original B line |
[out] | nalines | number of new lines (ALines) |
[out] | nblines | number of new lines (BLines) |
with_z | 3D, not supported! |
Definition at line 660 of file vector/Vlib/intersect.c.
References l, x, and line_pnts::y.
int Vect_segment_intersection | ( | double | ax1, |
double | ay1, | ||
double | az1, | ||
double | ax2, | ||
double | ay2, | ||
double | az2, | ||
double | bx1, | ||
double | by1, | ||
double | bz1, | ||
double | bx2, | ||
double | by2, | ||
double | bz2, | ||
double * | x1, | ||
double * | y1, | ||
double * | z1, | ||
double * | x2, | ||
double * | y2, | ||
double * | z2, | ||
int | with_z | ||
) |
Check for intersect of 2 line segments.
ax1,ay1,az1,ax2,ay2,az2 | input line a | |
bx1,by1,bz1,bx2,by2,bz2 | input line b | |
[out] | x1,y1,z1 | intersection point1 (case 2-4) |
[out] | x2,y2,z2 | intersection point2 (case 2-4) |
with_z | use z coordinate (3D) (TODO) |
Definition at line 111 of file vector/Vlib/intersect.c.