/**
* intersects a line with the polygon and gives back the two intersection points
* @return TRUE if two intersection can be found, else FALSE
* @param x, y intersection points
* @param a, b define the line to intersection
*/
static bool get_two_intersects(struct FloatVect2 *x, struct FloatVect2 *y, struct FloatVect2 a, struct FloatVect2 b)
{
int i, count = 0;
struct FloatVect2 tmp;
for (i = 0; i < survey.poly_count - 1; i++)
if (intercept_two_lines(&tmp, a, b, waypoints[survey.poly_first + i].x, waypoints[survey.poly_first + i].y,
waypoints[survey.poly_first + i + 1].x, waypoints[survey.poly_first + i + 1].y)) {
if (count == 0) {
*x = tmp;
count++;
} else {
*y = tmp;
count++;
break;
}
}
//wrapover first,last polygon waypoint
if (count == 1
&& intercept_two_lines(&tmp, a, b, waypoints[survey.poly_first + survey.poly_count - 1].x,
waypoints[survey.poly_first + survey.poly_count - 1].y, waypoints[survey.poly_first].x,
waypoints[survey.poly_first].y)) {
*y = tmp;
count++;
}
if (count != 2) {
return false;
}
//change points
if (fabs(survey.dir_vec.x) > fabs(survey.dir_vec.y)) {
if ((y->x - x->x) / survey.dir_vec.x < 0.0) {
tmp = *x;
*x = *y;
*y = tmp;
}
} else if ((y->y - x->y) / survey.dir_vec.y < 0.0) {
tmp = *x;
*x = *y;
*y = tmp;
}
return true;
}
/**
intersects a line with the polygon and gives back the two intersection points
returns : TRUE if two intersection can be found, else FALSE
x, y : intersection points
a, b : define the line to intersection
**/
static bool_t get_two_intersects(point2d *x, point2d *y, point2d a, point2d b)
{
int i, count = 0;
point2d tmp;
for (i=0;i<poly_count-1;i++)
if(intercept_two_lines(&tmp,a,b,waypoints[poly_first+i].x,waypoints[poly_first+i].y,waypoints[poly_first+i+1].x,waypoints[poly_first+i+1].y)) {
if (count == 0) {
*x = tmp;
count++;
}
else {
*y = tmp;
count++;
break;
}
}
//wrapover first,last polygon waypoint
if (count == 1 && intercept_two_lines(&tmp,a,b,waypoints[poly_first+poly_count-1].x,waypoints[poly_first+poly_count-1].y,waypoints[poly_first].x,waypoints[poly_first].y)) {
*y = tmp;
count++;
}
if (count != 2)
return FALSE;
//change points
if (fabs(dir_vec.x) > fabs(dir_vec.y)) {
if ((y->x - x->x) / dir_vec.x < 0.0){
tmp = *x;
*x = *y;
*y = tmp;
}
}
else
if ((y->y - x->y) / dir_vec.y < 0.0) {
tmp = *x;
*x = *y;
*y = tmp;
}
return TRUE;
}