public static bool InScanArea(TriangulationPoint pa, TriangulationPoint pb, TriangulationPoint pc,
TriangulationPoint pd)
{
double pdx = pd.X;
double pdy = pd.Y;
double adx = pa.X - pdx;
double ady = pa.Y - pdy;
double bdx = pb.X - pdx;
double bdy = pb.Y - pdy;
double adxbdy = adx*bdy;
double bdxady = bdx*ady;
double oabd = adxbdy - bdxady;
// oabd = orient2d(pa,pb,pd);
if (oabd <= 0)
{
return false;
}
double cdx = pc.X - pdx;
double cdy = pc.Y - pdy;
double cdxady = cdx*ady;
double adxcdy = adx*cdy;
double ocad = cdxady - adxcdy;
// ocad = orient2d(pc,pa,pd);
if (ocad <= 0)
{
return false;
}
return true;
}
private int FindIndex(PolygonPoint[] points, TriangulationPoint toFind)
{
for (int i = 0; i < points.Length; i++){
PolygonPoint p = points[i];
if (p == toFind) return i;
if (p.X != toFind.X) continue;
if (p.Y != toFind.Y) continue;
return i;
}
return -1;
}
/// <summary>
/// Requirements:
/// 1. a,b and c form a triangle.
/// 2. a and d is know to be on opposite side of bc
/// <code>
/// a
/// +
/// / \
/// / \
/// b/ \c
/// +-------+
/// / B \
/// / \
/// </code>
/// Facts:
/// d has to be in area B to have a chance to be inside the circle formed by a,b and c
/// d is outside B if orient2d(a,b,d) or orient2d(c,a,d) is CW
/// This preknowledge gives us a way to optimize the incircle test
/// </summary>
/// <param name="pa">triangle point, opposite d</param>
/// <param name="pb">triangle point</param>
/// <param name="pc">triangle point</param>
/// <param name="pd">point opposite a</param>
/// <returns>true if d is inside circle, false if on circle edge</returns>
public static bool SmartIncircle(TriangulationPoint pa, TriangulationPoint pb, TriangulationPoint pc,
TriangulationPoint pd)
{
double pdx = pd.X;
double pdy = pd.Y;
double adx = pa.X - pdx;
double ady = pa.Y - pdy;
double bdx = pb.X - pdx;
double bdy = pb.Y - pdy;
double adxbdy = adx*bdy;
double bdxady = bdx*ady;
double oabd = adxbdy - bdxady;
// oabd = orient2d(pa,pb,pd);
if (oabd <= 0) return false;
double cdx = pc.X - pdx;
double cdy = pc.Y - pdy;
double cdxady = cdx*ady;
double adxcdy = adx*cdy;
double ocad = cdxady - adxcdy;
// ocad = orient2d(pc,pa,pd);
if (ocad <= 0) return false;
double bdxcdy = bdx*cdy;
double cdxbdy = cdx*bdy;
double alift = adx*adx + ady*ady;
double blift = bdx*bdx + bdy*bdy;
double clift = cdx*cdx + cdy*cdy;
double det = alift*(bdxcdy - cdxbdy) + blift*ocad + clift*oabd;
return det > 0;
}
/// Forumla to calculate signed area
/// Positive if CCW
/// Negative if CW
/// 0 if collinear
/// A[P1,P2,P3] = (x1*y2 - y1*x2) + (x2*y3 - y2*x3) + (x3*y1 - y3*x1)
/// = (x1-x3)*(y2-y3) - (y1-y3)*(x2-x3)
public static Orientation Orient2d(TriangulationPoint pa, TriangulationPoint pb, TriangulationPoint pc)
{
double detleft = (pa.X - pc.X)*(pb.Y - pc.Y);
double detright = (pa.Y - pc.Y)*(pb.X - pc.X);
double val = detleft - detright;
if (val > -EPSILON && val < EPSILON)
{
return Orientation.Collinear;
}
else if (val > 0)
{
return Orientation.CCW;
}
return Orientation.CW;
}
public abstract TriangulationConstraint NewConstraint(TriangulationPoint a, TriangulationPoint b);
// ReSharper disable UnusedMethodReturnValue.Global
public abstract DTSweepConstraint NewConstraint(TriangulationPoint a, TriangulationPoint b);
public abstract TriangulationConstraint NewConstraint(TriangulationPoint a, TriangulationPoint b);
