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Yet more optimisations in getParameter(), both for straight lines and curves.

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This commit is contained in:
Jürg Lehni 2011-03-07 02:26:59 +00:00
parent 0e8c346888
commit add0bcf1fd
1 changed files with 12 additions and 5 deletions
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17
src/path/Curve.js
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@ -328,16 +328,23 @@ var Curve = this.Curve = Base.extend({
length) {
if (length <= 0)
return 0;
// TODO: Optimise for straight lines
var bezierLength = Curve.getLength(
p1x, p1y, c1x, c1y, c2x, c2y, p2x, p2y, 0, 1);
if (length >= bezierLength)
return 1;
if (p1x == c1x && p1y == c1y && p2x == c2x && p2y == c2y) {
// Straight line, calculate directly
var dx = p2x - p1x,
dy = p2y - p1y;
return Math.min(length / Math.sqrt(dx * dx + dy * dy), 1);
}
// Let's use the Van Wijngaarden–Dekker–Brent Method to find
// solutions more reliably than with False Position Method.
var ds = getLengthIntegrand(
p1x, p1y, c1x, c1y, c2x, c2y, p2x, p2y);
// Use integrand both to calculate total length and part lengths
// in f(t) below.
var bezierLength = Numerical.gauss(ds, 0, 1, 8);
if (length >= bezierLength)
return 1;
function f(t) {
// The precision of 5 iterations seems enough for this
return length - Numerical.gauss(ds, 0, t, 5);
}
// Use length / bezierLength for an initial guess for b, to