public Vector2 V2AddII(Vector2 a, Vector2 b) {
Vector2 c = new Vector2();
c.xset(a.xval() + b.xval());
c.yset(a.yval() + b.yval());
return (c);
}
public Vector2 V2ScaleIII(Vector2 a, double s) {
Vector2 result = new Vector2();
result.xset(s * a.xval());
result.yset(s * a.yval());
return (result);
}
/* return vector sum c = a+b */
public Vector2 V2Add(Vector2 a, Vector2 b, Vector2 c) {
// c = new Vector2();
c.xset(a.xval() + b.xval());
c.yset(a.yval() + b.yval());
// System.out.println("V2Add: "+a.xval()+" + "+b.xval()+" = "+c.xval() );
// System.out.println("V2Add: "+a.yval()+" + "+b.yval()+" = "+c.yval()+"\n");
return (c);
}
public Vector2 V2Scale(Vector2 v, double newlen) {
double len = v.V2Length();
if (len != 0.0) {
double temp;
temp = v.xval();
v.xset(temp * newlen / len);
temp = v.yval();
v.yset(temp * newlen / len);
}
return (v);
}
public Vector2 ComputeCenterTangent(Vector2[] d, int center)
/* d; Digitized points */
/*center; Index to point inside region */
{
Vector2 V1, V2, tHatCenter;
V1 = V2SubII(d[center - 1], d[center]);
V2 = V2SubII(d[center], d[center + 1]);
tHatCenter = new Vector2();
tHatCenter.xset((V1.xval() + V2.xval()) / 2.0);
tHatCenter.yset((V1.yval() + V2.yval()) / 2.0);
tHatCenter.V2Normalize();
return tHatCenter;
}
/*
* GenerateBezier :
* Use least-squares method to find Bezier control points for region.
*
*/
public Vector2[] GenerateBezier(
Vector2[] d, int first, int last, double uPrime[], Vector2 tHat1, Vector2 tHat2)
/* d: Array of digitized points */
/* first last: Indices defining region */
/* uPrime: Parameter values for region */
/* tHat1, tHat2: Unit tangents at endpoints */
{
int i;
double C[][] = new double[2][2]; /* Matrix C */
double[] X = new double[2]; /* Matrix X */
Vector2 A[][]; /* Precomputed rhs for eqn */
int nPts; /* Number of pts in sub-curve */
double det_C0_C1, /* Determinants of matrices */ det_C0_X, det_X_C1;
double alpha_l, /* Alpha values, left and right */ alpha_r;
Vector2 tmp; /* Utility variable */
Vector2[] bezCurve = new Vector2[4]; /* RETURN bezier curve ctl pts */
// System.out.println("ENTERING GENERATE BEZIER "+tHat1.xval()+" "+tHat1.yval()+"
// "+tHat2.xval()+" "+tHat2.yval());
for (i = 0; i < 4; i++) bezCurve[i] = new Vector2();
/* bezCurve = (Vector2 *)malloc(4 * sizeof(Vector2)); */
nPts = last - first + 1;
A = new Vector2[nPts][2];
/* Compute the A's */
for (i = 0; i < nPts; i++) {
Vector2 v1 = new Vector2();
Vector2 v2 = new Vector2();
v1.xset(tHat1.xval());
v1.yset(tHat1.yval());
v2.xset(tHat2.xval());
v2.yset(tHat2.yval());
// System.out.println("PT: "+i);
// System.out.print("that1 length "+tHat1.V2Length()+" "+tHat1.xval()+" "+tHat1.yval() );
// System.out.print("that2 length "+tHat2.V2Length()+" "+tHat2.xval()+" "+tHat2.yval() );
// System.out.print("Before: "+v1.xval() +" "+v1.yval() );
V2Scale(v1, B1(uPrime[i]));
// System.out.println("after : "+v1.xval() +" "+v1.yval() );
// System.out.print("Before: "+v2.xval() +" "+v2.yval() );
V2Scale(v2, B2(uPrime[i]));
// System.out.println("after : "+v2.xval() +" "+v2.yval() );
A[i][0] = new Vector2();
A[i][0].xset(v1.xval());
A[i][0].yset(v1.yval());
A[i][1] = new Vector2();
A[i][1].xset(v2.xval());
A[i][1].yset(v2.yval());
// System.out.println("A[i][0] "+A[i][0].xval()+" "+A[i][0].yval());
// System.out.println("A[i][1] "+A[i][1].xval()+" "+A[i][1].yval());
// System.out.println("B1 "+B1(uPrime[i])+" B2 "+B2(uPrime[i]));
}
/* Create the C and X matrices */
C[0][0] = 0.0;
C[0][1] = 0.0;
C[1][0] = 0.0;
C[1][1] = 0.0;
X[0] = 0.0;
X[1] = 0.0;
for (i = 0; i < nPts; i++) {
C[0][0] += V2Dot(A[i][0], A[i][0]);
C[0][1] += V2Dot(A[i][0], A[i][1]);
/* C[1][0] += V2Dot(A[i][0], A[i][1]);*/
C[1][0] = C[0][1];
C[1][1] += V2Dot(A[i][1], A[i][1]);
tmp =
V2SubII(
d[first + i],
V2AddII(
V2ScaleIII(d[first], B0(uPrime[i])),
V2AddII(
V2ScaleIII(d[first], B1(uPrime[i])),
V2AddII(
V2ScaleIII(d[last], B2(uPrime[i])),
V2ScaleIII(d[last], B3(uPrime[i]))))));
X[0] += V2Dot(A[i][0], tmp);
X[1] += V2Dot(A[i][1], tmp);
}
System.out.println("C " + C[0][0] + " " + C[0][1] + " " + C[1][0] + " " + C[1][1]);
System.out.println("X " + X[0] + " " + X[1]);
/* Compute the determinants of C and X */
det_C0_C1 = C[0][0] * C[1][1] - C[1][0] * C[0][1];
det_C0_X = C[0][0] * X[1] - C[0][1] * X[0];
det_X_C1 = X[0] * C[1][1] - X[1] * C[0][1];
/* Finally, derive alpha values */
if (det_C0_C1 == 0.0) {
det_C0_C1 = (C[0][0] * C[1][1]) * 10e-12;
}
alpha_l = det_X_C1 / det_C0_C1;
alpha_r = det_C0_X / det_C0_C1;
// System.out.println("\n\n\nalpha_l "+alpha_l+" alpha_r "+alpha_r);
/* If alpha negative, use the Wu/Barsky heuristic (see text) */
if (alpha_l < 0.0 || alpha_r < 0.0) {
int ddd;
double dist = V2DistanceBetween2Points(d[last], d[first]) / 3.0;
for (ddd = 0; ddd < 4; ddd++) bezCurve[ddd] = new Vector2();
bezCurve[0] = d[first];
bezCurve[3] = d[last];
// System.out.println("HERE!!!!");
V2Add(bezCurve[0], V2Scale(tHat1, dist), bezCurve[1]);
V2Add(bezCurve[3], V2Scale(tHat2, dist), bezCurve[2]);
return (bezCurve);
}
/* First and last control points of the Bezier curve are */
/* positioned exactly at the first and last data points */
/* Control points 1 and 2 are positioned an alpha distance out */
/* on the tangent vectors, left and right, respectively */
bezCurve[0] = new Vector2();
bezCurve[1] = new Vector2();
bezCurve[2] = new Vector2();
bezCurve[3] = new Vector2();
bezCurve[0].xset(d[first].xval());
bezCurve[0].yset(d[first].yval());
bezCurve[3].xset(d[last].xval());
bezCurve[3].yset(d[last].yval());
// System.out.println("EDW??? 1");
V2Add(bezCurve[0], V2Scale(tHat1, alpha_l), bezCurve[1]);
// System.out.println("EDW??? 2");
V2Add(bezCurve[3], V2Scale(tHat2, alpha_r), bezCurve[2]);
// System.out.println("BEZ_CURVE is "+bezCurve[0].xval()+" "+bezCurve[0].yval()+" and
// "+bezCurve[3].xval()+" "+bezCurve[3].yval());
// System.out.println("BEZ_CURVE is "+bezCurve[1].xval()+" "+bezCurve[1].yval()+" and
// "+bezCurve[2].xval()+" "+bezCurve[2].yval());
// System.out.println("EXITING GENERATE BEZIER");
return (bezCurve);
}
