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Add comments to fat-line clipping code linking to issues #568 and #571.

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This commit is contained in:
Jürg Lehni 2015-01-02 22:34:09 +01:00
parent cdfd21ddd3
commit 232739fae9
1 changed files with 9 additions and 4 deletions
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13
src/path/Curve.js
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@ -1066,7 +1066,7 @@ new function() { // Scope for methods that require numerical integration
// Let P be the first curve and Q be the second
var q0x = v2[0], q0y = v2[1], q3x = v2[6], q3y = v2[7],
tolerance = /*#=*/Numerical.TOLERANCE,
hullEpsilon = 1e-9,
epsilon = 1e-10, // /*#=*/Numerical.EPSILON,
// Calculate the fat-line L for Q is the baseline l and two
// offsets which completely encloses the curve P.
d1 = getSignedDistance(q0x, q0y, q3x, q3y, v2[2], v2[3]) || 0,
@ -1082,7 +1082,9 @@ new function() { // Scope for methods that require numerical integration
dp2 = getSignedDistance(q0x, q0y, q3x, q3y, v1[4], v1[5]),
dp3 = getSignedDistance(q0x, q0y, q3x, q3y, v1[6], v1[7]),
tMinNew, tMaxNew, tDiff;
if (q0x === q3x && uMax - uMin <= hullEpsilon && recursion > 4) {
// NOTE: the recursion threshold of 4 is needed to prevent issue #571
// from occurring: https://github.com/paperjs/paper.js/issues/571
if (q0x === q3x && uMax - uMin <= epsilon && recursion > 4) {
// The fatline of Q has converged to a point, the clipping is not
// reliable. Return the value we have even though we will miss the
// precision.
@ -1101,7 +1103,7 @@ new function() { // Scope for methods that require numerical integration
tMaxClip = clipConvexHull(top, bottom, dMin, dMax);
// No intersections if one of the tvalues are null or 'undefined'
if (tMinClip == null || tMaxClip == null)
return false;
return;
// Clip P with the fatline for Q
v1 = Curve.getPart(v1, tMinClip, tMaxClip);
tDiff = tMaxClip - tMinClip;
@ -1132,7 +1134,10 @@ new function() { // Scope for methods that require numerical integration
parts[1], v1, curve2, curve1, locations, include,
t, uMax, tMinNew, tMaxNew, tDiff, !reverse, recursion);
}
} else if (Math.max(uMax - uMin, tMaxNew - tMinNew) < tolerance) {
} else if (Math.max(uMax - uMin, tMaxNew - tMinNew) < tolerance / 2) {
// NOTE: Not sure why we compare with half the tolerance here, but
// it appears to be needed to fix issue #568 (intersection is found
// twice): https://github.com/paperjs/paper.js/issues/568
// We have isolated the intersection with sufficient precision
var t1 = tMinNew + (tMaxNew - tMinNew) / 2,
t2 = uMin + (uMax - uMin) / 2;