public SplitType SplitWithPlane(Plane3D plane, out Polygon3D front, out Polygon3D back,
bool veryPrecise)
{
Vector3D intersection;
front = null;
back = null;
double dist = 0;
double maxDist = 0;
double minDist = 0;
double prevDist;
double threshold;
VType status;
VType prevStatus = VType.Either;
// double scale
if (veryPrecise)
{
threshold = 0.01;
}
else
{
threshold = 0.25;
}
for (int i = 0; i < vertices.Count; i++)
{
dist = plane.GetDistanceToPoint(vertices[i]);
if (i == 0 || dist > maxDist)
{
maxDist = dist;
}
if (i == 0 || dist < minDist)
{
minDist = dist;
}
if (dist > +threshold)
{
prevStatus = VType.Front;
}
else if (dist < -threshold)
{
prevStatus = VType.Back;
}
}
if (maxDist < threshold && minDist > -threshold)
{
return(SplitType.SP_Coplanar);
}
else if (maxDist < threshold)
{
return(SplitType.SP_Back);
}
else if (minDist > -threshold)
{
return(SplitType.SP_Front);
}
else
{
front = Clone();
front.vertices.Clear();
back = Clone();
back.vertices.Clear();
int j = vertices.Count - 1;
for (int i = 0; i < vertices.Count; i++)
{
prevDist = dist;
dist = plane.GetDistanceToPoint(vertices[i]);
if (dist > +threshold)
{
status = VType.Front;
}
else if (dist < -threshold)
{
status = VType.Back;
}
else
{
status = prevStatus;
}
if (status != prevStatus)
{
// Crossing. Either Front-to-Back or Back-To-Front.
// Intersection point is naturally on both front and back polys.
if ((dist >= -threshold) && (dist < +threshold))
{
// This point lies on plane.
if (prevStatus == VType.Front)
{
front.vertices.Add(vertices[i]);
back.vertices.Add(vertices[i]);
}
else
{
back.vertices.Add(vertices[i]);
front.vertices.Add(vertices[i]);
}
}
else if ((prevDist >= -threshold) && (prevDist < +threshold))
{
// Previous point lies on plane.
if (status == VType.Front)
{
front.vertices.Add(vertices[j]);
front.vertices.Add(vertices[i]);
}
else
{
back.vertices.Add(vertices[j]);
back.vertices.Add(vertices[i]);
}
}
else
{
// Intersection point is in between.
intersection = plane.LineIntersection(vertices[j], vertices[i]);
if (prevStatus == VType.Front)
{
front.vertices.Add(intersection);
back.vertices.Add(intersection);
back.vertices.Add(vertices[i]);
}
else
{
back.vertices.Add(intersection);
front.vertices.Add(intersection);
front.vertices.Add(vertices[i]);
}
}
}
else
{
if (status == VType.Front)
{
front.vertices.Add(vertices[i]);
}
else
{
back.vertices.Add(vertices[i]);
}
}
j = i;
prevStatus = status;
}
// Handle possibility of sliver polys due to precision errors.
if (front.Fix() < 3)
{
return(SplitType.SP_Back);
}
else if (back.Fix() < 3)
{
return(SplitType.SP_Front);
}
else
{
return(SplitType.SP_Split);
}
}
}