bool PointInPolygon( const vec2d & R, const std::vector< vec2d > & pnts )
{
// Implementation of Algorithm 6 from "The Point in Polygon Problem
// for Arbitrary Polygons" by Hormann and Agathos.
//
// R: the point in question
// pnts: vector of points defining polygon, first and last point should be the same
//
// Note: This algorithm does not test to see if the test point lies on the
// an edge of the polygon
int w = 0; // winding number
bool modify_w = false;
for ( int i = 0; i < ( int )pnts.size() - 1; i++ )
{
if ( ( pnts[i].y() < R.y() ) != ( pnts[i + 1].y() < R.y() ) ) // if crossing
{
if ( pnts[i].x() >= R.x() )
{
if ( pnts[i + 1].x() > R.x() )
{
modify_w = true;
}
else if ( ( det( pnts[i], pnts[i + 1], R ) > 0 ) == ( pnts[i + 1].y() > pnts[i].y() ) ) // right crossing
{
modify_w = true;
}
}
else if ( pnts[i + 1].x() > R.x() )
{
if ( ( det( pnts[i], pnts[i + 1], R ) > 0 ) == ( pnts[i + 1].y() > pnts[i].y() ) ) // right crossing
{
modify_w = true;
}
}
}
if ( modify_w )
{
w = w + 2 * ( pnts[i + 1].y() > pnts[i].y() ) - 1; // modify w
}
modify_w = false;
}
return !!(abs( w % 2 ));
}
vec3d MapFromPlane( vec2d & uw, vec3d & B, vec3d & e0, vec3d & e1 )
{
vec3d result = B + e0 * uw.x() + e1 * uw.y();
return result;
}
