private void construct(EdDisc a, EdDisc b) {
this.discA = a;
this.discB = b;
if (EdDisc.partiallyDisjoint(a, b)) {
// if (!UHullMain.oldBitanMethod())
{
final boolean db = false;
if (a.getRadius() == b.getRadius()) {
FPoint2 oa = a.getOrigin(), ob = b.getOrigin();
FPoint2 n = new FPoint2(-(ob.y - oa.y), ob.x - oa.x);
n.normalize();
n.x *= a.getRadius();
n.y *= a.getRadius();
seg = new DirSeg(FPoint2.add(oa, n, null), FPoint2.add(ob, n, null));
return;
}
boolean swap = a.getRadius() > b.getRadius();
if (swap) {
b = (EdDisc) discA;
a = (EdDisc) discB;
}
if (db && T.update())
T.msg(
"BiTangent construct, arad="
+ Tools.f(a.getRadius())
+ " brad="
+ Tools.f(b.getRadius())
+ " swap="
+ swap
+ " origin.a="
+ T.show(a.getOrigin()));
FPoint2 oa = a.getOrigin();
FPoint2 ob = b.getOrigin();
double U = ob.x, V = ob.y;
double A = oa.x - U, B = oa.y - V;
double R1 = a.getRadius();
double R2 = b.getRadius();
double S = R2 - R1;
double x1, y1, x2, y2;
x1 = A;
y1 = B;
boolean secondRoot;
boolean altSlope = Math.abs(B) < Math.abs(A);
if (!altSlope) {
double C1 = S * S / B, C2 = -A / B;
double qA = 1 + C2 * C2, qB = 2 * C1 * C2, qC = C1 * C1 - S * S;
double root = Math.sqrt(qB * qB - 4 * qA * qC);
x2 = (-qB - root) / (2 * qA);
y2 = C1 + C2 * x2;
secondRoot = MyMath.sideOfLine(x2, y2, A, B, 0, 0) < 0;
if (swap ^ secondRoot) {
x2 = (-qB + root) / (2 * qA);
y2 = C1 + C2 * x2;
}
} else {
double C1 = S * S / A, C2 = -B / A;
double qA = 1 + C2 * C2, qB = 2 * C1 * C2, qC = C1 * C1 - S * S;
double root = Math.sqrt(qB * qB - 4 * qA * qC);
y2 = (-qB - root) / (2 * qA);
x2 = C1 + C2 * y2;
secondRoot = MyMath.sideOfLine(x2, y2, A, B, 0, 0) < 0;
if (swap ^ secondRoot) {
y2 = (-qB + root) / (2 * qA);
x2 = C1 + C2 * y2;
}
}
// now grow both discs back to r1, r2
double tx = U;
double ty = V;
// if (S == 0) {
// FPoint2 unit = new FPoint2(-A, -B);
// if (swap) {
// unit.x = -unit.x;
// unit.y = -unit.y;
// }
// unit.normalize();
// tx += -unit.y * R1;
// ty += unit.x * R1;
// } else
{
double F = R1 / S;
tx += x2 * F;
ty += y2 * F;
}
if (db && T.update())
T.msg("adding offset to both points: " + tx + ", " + ty + T.show(new FPoint2(tx, ty)));
x1 += tx;
y1 += ty;
x2 += tx;
y2 += ty;
FPoint2 p1 = new FPoint2(x1, y1);
FPoint2 p2 = new FPoint2(x2, y2);
if (swap) {
FPoint2 tmp = p1;
p1 = p2;
p2 = tmp;
}
seg = new DirSeg(p1, p2);
if (db && T.update())
T.msg(
"swap="
+ swap
+ " altSlope="
+ altSlope
+ " secondRoot="
+ secondRoot
+ " dirseg="
+ EdSegment.showDirected(p1, p2));
}
// else {
//
// double th = calcTheta(a, b);
// LineEqn eqn = new LineEqn(a.polarPoint(th + Math.PI / 2), th);
// double ta = eqn.parameterFor(a.getOrigin());
// double tb = eqn.parameterFor(b.getOrigin());
// seg = new DirSeg(eqn.pt(ta), eqn.pt(tb));
//
// }
}
}
private static String tl(FPoint2 rayStart, FPoint2 rayEnd) {
return EdSegment.showDirected(rayStart, rayEnd, null, -1);
}