/// <summary>
/// Determine whether the line connecting pt0 to pt1 intersects the plane
/// </summary>
/// <param name="pt0"></param>
/// <param name="pt1"></param>
/// <returns></returns>
public bool IsIntersection(Vector3D pt0, Vector3D pt1)
{
int sign0 = (int)Math3D.GetSign(GetDistanceToPlane(pt0));
int sign1 = (int)Math3D.GetSign(GetDistanceToPlane(pt1));
return((sign0 < 0 && sign1 > 0) || (sign0 > 0 && sign1 <= 0));
}
//--------------------------------------------------------------------------------
/// <summary>
/// Clip the given polygon by the plane so that only the regions
/// located positive of the plane remain.
/// </summary>
/// <param name="polygon"></param>
public void ClipPolygon(Polygon3D polygon)
{
Vector3D ptNormal = polygon.GetNormal();
Vector3DCollection vNewPoints = new Vector3DCollection();
int iPoints = polygon.Points.Count;
for (int i = 0; i < iPoints; i++)
{
Vector3D pt0 = polygon.Points[(i + iPoints - 1) % iPoints];
Vector3D pt1 = polygon.Points[i];
int sign0 = (int)Math3D.GetSign(this.GetDistanceToPlane(pt0), Math3D.EpsilonF);
int sign1 = (int)Math3D.GetSign(this.GetDistanceToPlane(pt1), Math3D.EpsilonF);
if (sign0 > 0)
{
// line is infront
if (sign1 >= 0)
{
vNewPoints.Add(pt1);
}
// line is entering plane
else if (sign1 < 0)
{
Debug.Assert(sign0 > 0 && sign1 < 0);
vNewPoints.Add(this.GetIntersection(pt0, pt1));
}
}
else if (sign0 == 0)
{
// line is infront
if (sign1 > 0)
{
vNewPoints.Add(pt1);
}
// line is coplanar
else if (sign1 == 0)
{
vNewPoints.Add(pt1);
}
// line is behind
else if (sign1 < 0)
{
}
}
else if (sign0 < 0)
{
// line is leaving plane
if (sign1 > 0)
{
Debug.Assert(sign0 < 0 && sign1 > 0);
vNewPoints.Add(this.GetIntersection(pt0, pt1));
vNewPoints.Add(pt1);
}
// line is leaving plane
else if (sign1 == 0)
{
vNewPoints.Add(pt1);
}
// line is behind
else if (sign1 < 0)
{
}
}
}
// set new points
polygon.Points.Clear();
polygon.Points.AddRange(vNewPoints);
/*if( this.Points.Count >= 3 ) {
* if( Vector3D.Dot( this.GetNormal(), ptNormal ) < 0 ) {
* this.Flip();
* }
* } */
polygon.Optimize();
}
/// <summary>
/// Get the sign of the point in relation to the plane
/// </summary>
/// <param name="pt"></param>
/// <returns></returns>
public Sign GetSign(Vector3D pt)
{
return(Math3D.GetSign(GetDistanceToPlane(pt), Math3D.EpsilonF));
}