scratchfoundation/paper.js
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Correct winding number calculation when horizontal curves are involved.

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hkrish 2014-02-24 19:08:39 +01:00
parent 81137ce7fc
commit cac86627be
1 changed files with 10 additions and 3 deletions
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13
src/path/PathItem.Boolean.js
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@ -258,7 +258,9 @@ PathItem.inject(new function() {
windLeft = 0, windLeft = 0,
windRight = 0, windRight = 0,
roots = [], roots = [],
abs = Math.abs; abs = Math.abs,
ONE = 1 - TOLERANCE,
rootMaxLimit = ONE;
// Absolutely horizontal curves may return wrong results, since // Absolutely horizontal curves may return wrong results, since
// the curves are monotonic in y direction and this is an // the curves are monotonic in y direction and this is an
// indeterminate state. // indeterminate state.
@ -298,7 +300,8 @@ PathItem.inject(new function() {
for (var i = 0, l = curves.length; i < l; i++) { for (var i = 0, l = curves.length; i < l; i++) {
var curve = curves[i], var curve = curves[i],
values = curve.values, values = curve.values,
winding = curve.winding; winding = curve.winding,
next = curve.next;
// Since the curves are monotone in y direction, we can just // Since the curves are monotone in y direction, we can just
// compare the endpoints of the curve to determine if the // compare the endpoints of the curve to determine if the
// ray from query point along +-x direction will intersect // ray from query point along +-x direction will intersect
@ -306,8 +309,12 @@ PathItem.inject(new function() {
var interceptTest = winding === 1 var interceptTest = winding === 1
? (y >= values[1] && y <= values[7]) ? (y >= values[1] && y <= values[7])
: (y >= values[7] && y <= values[1]); : (y >= values[7] && y <= values[1]);
// If the next curve is horizontal, we have to include the end
// points of this curve to make sure we won't miss an intercept
rootMaxLimit = (next.winding === 0 && next.values[1] === y)
? 1 : ONE;
if (winding !== 0 && interceptTest && Curve.solveCubic( if (winding !== 0 && interceptTest && Curve.solveCubic(
values, 1, y, roots, 0, 1 - TOLERANCE) === 1) { values, 1, y, roots, 0, rootMaxLimit) === 1) {
var t = roots[0], var t = roots[0],
x0 = Curve.evaluate(values, t, 0).x, x0 = Curve.evaluate(values, t, 0).x,
slope = Curve.evaluate(values, t, 1).y; slope = Curve.evaluate(values, t, 1).y;