/* Function used for Sort2
*/
private int Compare2(cVertex tpi, cVertex tpj)
{
int a = 0; /* TriangleSign result */
float x = 0, y = 0; /* projections in 1st quadrant */
cVertex pi, pj;
pi = tpi;
pj = tpj;
cPointi Origin = new cPointi();
/* A vector in the open upper halfplane is after
* a vector in the closed lower halfplane. */
if ((pi.Point.Y > 0) && (pj.Point.Y <= 0))
{
return(1);
}
else if ((pi.Point.Y <= 0) && (pj.Point.Y > 0))
{
return(-1);
}
/* A vector on the x-axis and one in the lower halfplane
* are handled by the Left computation below. */
/* Both vectors on the x-axis requires special handling. */
else if ((pi.Point.Y == 0) && (pj.Point.Y == 0))
{
if ((pi.Point.X < 0) && (pj.Point.X > 0))
{
return(-1);
}
if ((pi.Point.X > 0) && (pj.Point.X < 0))
{
return(1);
}
else if (Math.Abs(pi.Point.X) < Math.Abs(pj.Point.X))
{
return(-1);
}
else if (Math.Abs(pi.Point.X) > Math.Abs(pj.Point.X))
{
return(1);
}
else
{
return(0);
}
}
/* Otherwise, both in open upper halfplane,
* or both in closed lower halfplane, but not both on x-axis. */
else
{
a = Origin.TriangleSign(Origin, pi.Point, pj.Point);
if (a > 0)
{
return(-1);
}
else if (a < 0)
{
return(1);
}
else
{ /* Begin collinear */
x = Math.Abs(pi.Point.X) - Math.Abs(pj.Point.X);
y = Math.Abs(pi.Point.Y) - Math.Abs(pj.Point.Y);
if ((x < 0) || (y < 0))
{
return(-1);
}
else if ((x > 0) || (y > 0))
{
return(1);
}
else /* points are coincident */
{
return(0);
}
} /* End collinear */
}
}
/*---------------------------------------------------------------------
* Consult the book for explanations
*--------------------------------------------------------------------*/
private void ConvexIntersect(cVertexList P, cVertexList Q, int n, int m)
/* P has n pointCloud, Q has m pointCloud. */
{
/* Initialize variables. */
a = new cVertex();
b = new cVertex();
a = P.head; b = Q.head;
aa = ba = 0;
Origin = new cPointi(); /* (0,0) */
inflag = new cInFlag();
FirstPoint = true;
cVertex a1, b1;
A = new cPointi();
B = new cPointi();
p = new cPointd();
q = new cPointd();
p0 = new cPointd();
do
{
/* System.Diagnostics.Debug.WriteLine("Before Advances:a="+a.v.x+","+a.v.y+
* ", b="+b.v.x+","+b.v.y+"; aa="+aa+", ba="+ba+"; inflag="+
* inflag.f); */
/* Computations of key variables. */
a1 = a.PrevVertex;
b1 = b.PrevVertex;
SubVec(a.Point, a1.Point, A);
SubVec(b.Point, b1.Point, B);
cross = Origin.TriangleSign(Origin, A, B);
aHB = b1.Point.TriangleSign(b1.Point, b.Point, a.Point);
bHA = a1.Point.TriangleSign(a1.Point, a.Point, b.Point);
System.Diagnostics.Debug.WriteLine("cross=" + cross + ", aHB=" + aHB + ", bHA=" + bHA);
/* If A & B intersect, update inflag. */
code = a1.Point.SegSegInt(a1.Point, a.Point, b1.Point, b.Point, p, q);
System.Diagnostics.Debug.WriteLine("SegSegInt: code = " + code);
if (code == '1' || code == 'v')
{
if (inflag.f == cInFlag.Unknown && FirstPoint)
{
aa = ba = 0;
FirstPoint = false;
p0.x = p.x; p0.y = p.y;
InsertInters(p0.x, p0.y);
}
inflag = InOut(p, inflag, aHB, bHA);
System.Diagnostics.Debug.WriteLine("InOut sets inflag=" + inflag.f);
}
/*-----Advance rules-----*/
/* Special case: A & B overlap and oppositely oriented. */
if ((code == 'e') && (Dot(A, B) < 0))
{
InsertSharedSeg(p, q);
return;
}
/* Special case: A & B parallel and separated. */
if ((cross == 0) && (aHB < 0) && (bHA < 0))
{
System.Diagnostics.Debug.WriteLine("P and Q are disjoint.");
return;
}
/* Special case: A & B collinear. */
else if ((cross == 0) && (aHB == 0) && (bHA == 0))
{
/* Advance but do not output point. */
if (inflag.f == cInFlag.Pin)
{
b = Advance(b, "ba", inflag.f == cInFlag.Qin, b.Point);
}
else
{
a = Advance(a, "aa", inflag.f == cInFlag.Pin, a.Point);
}
}
/* Generic cases. */
else if (cross >= 0)
{
if (bHA > 0)
{
a = Advance(a, "aa", inflag.f == cInFlag.Pin, a.Point);
}
else
{
b = Advance(b, "ba", inflag.f == cInFlag.Qin, b.Point);
}
}
else /* if ( cross < 0 ) */
{
if (aHB > 0)
{
b = Advance(b, "ba", inflag.f == cInFlag.Qin, b.Point);
}
else
{
a = Advance(a, "aa", inflag.f == cInFlag.Pin, a.Point);
}
}
System.Diagnostics.Debug.WriteLine("After advances:a=(" + a.Point.X + ", " + a.Point.Y +
"), b=(" + b.Point.X + ", " + b.Point.Y + "); aa=" + aa +
", ba=" + ba + "; inflag=" + inflag.f);
/* Quit when both adv. indices have cycled, or one has cycled twice. */
} while (((aa < n) || (ba < m)) && (aa < 2 * n) && (ba < 2 * m));
if (!FirstPoint) /* If at least one point output, close up. */
{
InsertInters(p0.x, p0.y);
}
/* Deal with special cases: not implemented. */
if (inflag.f == cInFlag.Unknown)
{
System.Diagnostics.Debug.WriteLine("The boundaries of P and Q do not cross.");
intersection = false;
}
}
