line.h

source code to compute the visibility polygon of a point in a polygon.

/* Brian O'Connor
 * 
 * line.h: structures and functions for working with lines 
 *
 * IMPORTANT: all Points are assumed to be homogenous in this module. 
 */

#include "input.h"

#ifndef LINE_H
#define LINE_H

class Obstacle;
class Cell;

class Line {
public:

	Line(void) {};
	Line(Point *p1, Point *p2);

	Point *A; /* endpoints */
	Point *B;

	double length; /* used in computing intersections */
	Obstacle *ob;

	double a; /* line coordinates: a + bx + cy = 0 */
	double b;
	double c;
};

/* functions to encapsulate floating pt error */
int FloatCompare(double m, double n);

int FloatEqual(double m, double n);

/* create a new line from 2 pts */
Line *PointsToLine(Point *p1, Point *p2);

Point *NewPoint(void);
int PointCompare(Point *p1, Point *p2);
int PointEqual(Point *p1, Point *p2);

/* return TRUE if segments intersect w. intersection point returned in
	result */
int SegmentIntersection(Line *l1, Line *l2, Point *result);

/* return TRUE if segment s intersects line l & also return int. point */
int LineSegIntersection(Line *l, Line *s, Point *result);

/* return Point where the given lines intersect in result */ 
void LineIntersection(Line *l1, Line *l2, Point *result);

/* return Point where the given lines intersect in result, and 
   return the distance from l1->A endpoint to result (positive 
   direction is direction from A to B).  */
void LineIntersectionDistance(Line *l1, Line *l2, Point *result, double *dist);


/* returns the Distance from p1 to p2 */
double LineDistance(Point *p1, Point *p2);

/* returns TRUE if the given point is on the line segment, and false
 * if not. */
int PointOnSegment(Line *l, Point *p);

/* returns the angle made by the two lines. */
double LineAngle(Line *l1, Line *l2);

/* returns TRUE if the line segments overlap, and returns the endpoints
 * of the combined segment in pmin, pmax */
int LinesOverlap(Line *l1, Line *l2, Point **pmin, Point **pmax);

/* ASSERTs if the line is not valid (endpoints don't satisfy line eq)
 * and optionally can print out the Line structure. */ 
void VerifyLine(Line *l);
void DotProductTest(void);

#endif