scratchfoundation/paper.js
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Handle overlapping intercepts in getIntersection,

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In a more robust way. Restricting ranges in parameter is not a nice way
to handle endpoint intersections.
This commit is contained in:
hkrish 2014-05-17 13:43:46 +02:00
parent e5e2a8d7d4
commit 6c6ad76c94
1 changed files with 26 additions and 19 deletions
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45
src/path/PathItem.Boolean.js
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@ -229,7 +229,8 @@ PathItem.inject(new function() {
windRight = 0, windRight = 0,
roots = [], roots = [],
abs = Math.abs, abs = Math.abs,
MAX = 1 - TOLERANCE; tMin = TOLERANCE,
tMax = 1 - TOLERANCE;
// 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.
@ -270,7 +271,8 @@ PathItem.inject(new function() {
var curve = curves[i], var curve = curves[i],
values = curve.values, values = curve.values,
winding = curve.winding, winding = curve.winding,
next = curve.next; next = curve.next,
lastT, lastX0;
// 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
@ -278,30 +280,35 @@ PathItem.inject(new function() {
if (winding && (winding === 1 if (winding && (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])
&& Curve.solveCubic(values, 1, y, roots, 0, && Curve.solveCubic(values, 1, y, roots, 0, 1) === 1){
// If the next curve is horizontal, we have to include
// the end of this curve to make sure we won't miss an
// intercept.
!next.winding && next.values[1] === y ? 1 : MAX) === 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;
// Take care of cases where the curve and the preceding // Due to numerical precision issues, two consecutive curves
// curve merely touches the ray towards +-x direction, but // may register an intercept twice, at t = 1 and 0, if y is
// proceeds to the same side of the ray. This essentially is // almost equal to one of the endpoints of the curves.
// not a crossing. if (!(lastT && abs(lastX0 - x0) < TOLERANCE
if (abs(slope) < TOLERANCE && !Curve.isLinear(values) && ((lastT <= tMin && t >= tMax)
|| (t <= tMin && lastT >= tMax)))) {
// Take care of cases where the curve and the preceding
// curve merely touches the ray towards +-x direction, but
// proceeds to the same side of the ray. This essentially is
// not a crossing.
if (abs(slope) < TOLERANCE && !Curve.isLinear(values)
|| t < TOLERANCE && slope * Curve.evaluate( || t < TOLERANCE && slope * Curve.evaluate(
curve.previous.values, t, 1).y < 0) { curve.previous.values, t, 1).y < 0) {
if (testContains && x0 >= xBefore && x0 <= xAfter) { if (testContains && x0 >= xBefore && x0 <= xAfter) {
++windLeft; ++windLeft;
++windRight; ++windRight;
}
} else if (x0 <= xBefore) {
windLeft += winding;
} else if (x0 >= xAfter) {
windRight += winding;
} }
} else if (x0 <= xBefore) {
windLeft += winding;
} else if (x0 >= xAfter) {
windRight += winding;
} }
lastT = t;
lastX0 = x0;
} }
} }
} }