bool
JarvisMarch::
isLess(const Vec& p1, const Vec& p2)
throw()
{
double f=cross(p1,p2);
return f>0 || (EQDOUBLE(f,0) && isFurther(p1,p2));
}
// ----------------------------------------------------------------------
double
XYZFileElevation::
value( const shawn::Vec& p )
const throw()
{
double xlocal = (p.x()-base_point_.x())/x_scale_;
double ylocal = (p.y()-base_point_.y())/y_scale_;
int xcell = int(floor(xlocal));
int ycell = int(floor(ylocal));
double xfrac = xlocal-double(xcell);
double yfrac = ylocal-double(ycell);
if( EQDOUBLE(xfrac,0.0) && (xcell == xyz_data_->x_dimension()-1) )
{ --xcell; xfrac=1.0; }
if( EQDOUBLE(yfrac,0.0) && (ycell == xyz_data_->y_dimension()-1) )
{ --ycell; yfrac=1.0; }
if( (xcell<0) || (ycell<0) ||
(xcell>=xyz_data_->x_dimension()-1) ||
(ycell>=xyz_data_->y_dimension()-1) )
return 0.0;
if( xfrac > yfrac )
{
// lower triangle
double a = xyz_data_->value(xcell,ycell);
double b = xyz_data_->value(xcell+1,ycell);
double c = xyz_data_->value(xcell+1,ycell+1);
return (a + xfrac*(b-a) + yfrac*(c-b))*z_scale_ + base_point_.z();
}
else
{
// upper triangle
double a = xyz_data_->value(xcell,ycell);
double b = xyz_data_->value(xcell,ycell+1);
double c = xyz_data_->value(xcell+1,ycell+1);
return (a + yfrac*(b-a) + xfrac*(c-b))*z_scale_ + base_point_.z();
}
}
int
JarvisMarch::
index_of_lowest_point()
throw()
{
int i, min=0;
for (i=1; i<size_of_polygon_; i++){
if (polygon_[i].y()<polygon_[min].y() || (EQDOUBLE(polygon_[i].y(),polygon_[min].y()) && polygon_[i].x()<polygon_[min].x()))
{
min=i;
}
}
return min;
}
bool
Segment2D::
check_for_intersections(const Segment2D& p_seg, Vec& ipoint) const
throw()
{
if (equals(p_seg))
{
return true;
}
// compute point of intersection:
//xA = x1 + lambda*(x2-x1)
//yA = y1 + lambda*(y2-y1)
double x1 = source_.x();
double x2 = sink_.x();
double y1 = source_.y();
double y2 = sink_.y();
//xB = x3 + mue*(x4-x3)
//yB = y3 + mue*(y4-y3)
double x3 = p_seg.get_source().x();
double x4 = p_seg.get_sink().x();
double y3 = p_seg.get_source().y();
double y4 = p_seg.get_sink().y();
double mue = (x1*y2 + x2*y3 + x3*y1 - x2*y1 - x3*y2 - x1*y3) /
(x1*y4 + x4*y2 + x2*y3 + x3*y1 - x4*y1 - x1*y3 -x3*y2 - x2*y4);
double lambda = (x3 + mue*x4 - mue*x3 -x1) / (x2 - x1);
// s1: point of intersection located on this segment (owner)
double x_s1 = x1 + lambda*(x2-x1);
double y_s1 = y1 + lambda*(y2-y1);
// s2: point of intersection located on p_seg
double x_s2 = x3 + mue*(x4-x3);
double y_s2 = y3 + mue*(y4-y3);
//----------------------------------------------------------
// (s1==s2?)
if(EQDOUBLE(x_s1, x_s2) && EQDOUBLE(y_s1, y_s2))
{
//the point of intersection can not be an end point of a segment!
if( !((EQDOUBLE(x_s1, source_.x()) && EQDOUBLE(y_s1, source_.y()) ) || (EQDOUBLE(x_s1, sink_.x()) && EQDOUBLE(y_s1, sink_.y())) ))
{
// does the point of intersection s lie on both segments? (segments are no lines!)
Vec s;
s = Vec(x_s1, y_s1, 0.0);
if(point_on_segment(s) && p_seg.point_on_segment(s))
{
ipoint=s;
return true;
}
}
}
return false; // returns false if there does not exist any point of intersection between seg1 and seg2
}
