/// <summary>
/// Calculates all intersections between two polygons.
/// </summary>
/// <param name="polygon1">The first polygon.</param>
/// <param name="polygon2">The second polygon.</param>
/// <param name="slicedPoly1">Returns the first polygon with added intersection points.</param>
/// <param name="slicedPoly2">Returns the second polygon with added intersection points.</param>
private static void CalculateIntersections(Vertices polygon1, Vertices polygon2,
out Vertices slicedPoly1, out Vertices slicedPoly2)
{
slicedPoly1 = new Vertices(polygon1);
slicedPoly2 = new Vertices(polygon2);
// Iterate through polygon1's edges
for (int i = 0; i < polygon1.Count; i++)
{
// Get edge vertices
FPVector2 a = polygon1[i];
FPVector2 b = polygon1[polygon1.NextIndex(i)];
// Get intersections between this edge and polygon2
for (int j = 0; j < polygon2.Count; j++)
{
FPVector2 c = polygon2[j];
FPVector2 d = polygon2[polygon2.NextIndex(j)];
FPVector2 intersectionPoint;
// Check if the edges intersect
if (LineTools.LineIntersect(a, b, c, d, out intersectionPoint))
{
// calculate alpha values for sorting multiple intersections points on a edge
FP alpha;
// Insert intersection point into first polygon
alpha = GetAlpha(a, b, intersectionPoint);
if (alpha > 0f && alpha < 1f)
{
int index = slicedPoly1.IndexOf(a) + 1;
while (index < slicedPoly1.Count &&
GetAlpha(a, b, slicedPoly1[index]) <= alpha)
{
++index;
}
slicedPoly1.Insert(index, intersectionPoint);
}
// Insert intersection point into second polygon
alpha = GetAlpha(c, d, intersectionPoint);
if (alpha > 0f && alpha < 1f)
{
int index = slicedPoly2.IndexOf(c) + 1;
while (index < slicedPoly2.Count &&
GetAlpha(c, d, slicedPoly2[index]) <= alpha)
{
++index;
}
slicedPoly2.Insert(index, intersectionPoint);
}
}
}
}
// Check for very small edges
for (int i = 0; i < slicedPoly1.Count; ++i)
{
int iNext = slicedPoly1.NextIndex(i);
//If they are closer than the distance remove vertex
if ((slicedPoly1[iNext] - slicedPoly1[i]).LengthSquared() <= ClipperEpsilonSquared)
{
slicedPoly1.RemoveAt(i);
--i;
}
}
for (int i = 0; i < slicedPoly2.Count; ++i)
{
int iNext = slicedPoly2.NextIndex(i);
//If they are closer than the distance remove vertex
if ((slicedPoly2[iNext] - slicedPoly2[i]).LengthSquared() <= ClipperEpsilonSquared)
{
slicedPoly2.RemoveAt(i);
--i;
}
}
}
