scratchfoundation/paper.js
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Handle case of nearly singular matrix separately.

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Jürg Lehni 2011-06-05 21:45:29 +01:00
parent 27c7248a2d
commit 6ea63fde43
1 changed files with 21 additions and 7 deletions
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28
src/path/PathFitter.js
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@ -125,13 +125,27 @@ var PathFitter = Base.extend({
// Compute the determinants of C and X
var det_C0_C1 = C[0][0] * C[1][1] - C[1][0] * C[0][1],
det_C0_X = C[0][0] * X[1] - C[1][0] * X[0],
det_X_C1 = X[0] * C[1][1] - X[1] * C[0][1],
singularity = det_C0_C1 < Numerical.TOLERANCE;
// Finally, derive alpha values
var alpha_l = singularity ? 0 : det_X_C1 / det_C0_C1,
alpha_r = singularity ? 0 : det_C0_X / det_C0_C1;
alpha_l, alpha_r;
if (Math.abs(det_C0_C1) < Numerical.TOLERANCE) {
// Kramer's rule
var det_C0_X = C[0][0] * X[1] - C[1][0] * X[0],
det_X_C1 = X[0] * C[1][1] - X[1] * C[0][1];
// Derive alpha values
alpha_l = det_X_C1 / det_C0_C1;
alpha_r = det_C0_X / det_C0_C1;
} else {
// Matrix is under-determined, try assuming alpha_l == alpha_r
var c0 = C[0][0] + C[0][1],
c1 = C[1][0] + C[1][1];
if (Math.abs(c0) > Numerical.TOLERANCE) {
alpha_l = alpha_r = X[0] / c0;
} else if (Math.abs(c0) > Numerical.TOLERANCE) {
alpha_l = alpha_r = X[1] / c1;
} else {
// Handle below
alpha_l = alpha_r = 0.;
}
}
// If alpha negative, use the Wu/Barsky heuristic (see text)
// (if alpha is 0, you get coincident control points that lead to