scratchfoundation/paper.js
1
0
Fork 0
mirror of https://github.com/scratchfoundation/paper.js.git synced 2025-01-03 19:45:44 -05:00
Code Issues Projects Releases Packages Wiki Activity Actions

Merge pull request #895 from iconexperience/further-simplify-winding-calculation2

Browse source 
Further simplify and explain winding calculation in getWinding() (2)
This commit is contained in:
Jürg Lehni 2016-01-08 10:00:55 +01:00
commit 18e00f6312
1 changed files with 32 additions and 25 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

57
src/path/PathItem.Boolean.js
View file

@ -353,11 +353,11 @@ PathItem.inject(new function() {
// Retrieve and use it here (See _getMonoCurve()).
var curve = curves[start],
last = curve.last,
// Get the values of to the end x coordinate and winding of
// the last non-horizontal curve, which will be the previous
// non-horizontal curve for the first curve of the loop.
// Get the values of to the end x coordinate and winding of
// the last non-horizontal curve, which will be the previous
// non-horizontal curve for the first curve of the loop.
prevWinding = last.winding,
prevEnd = last.values[6];
prevXEnd = last.values[6];
end = start + curve.length;
for (var i = start; i < end; i++) {
var curve = curves[i],
@ -369,37 +369,44 @@ PathItem.inject(new function() {
// compare the endpoints of the curve to determine if the
// ray from query point along +-x direction will intersect
// the monotone curve.
// horizontal curves with winding == 0 will be completely
// ignored
if (winding && (py >= yStart && py <= yEnd
|| py >= yEnd && py <= yStart)) {
|| py >= yEnd && py <= yStart)) {
// calculate the x value for the ray's intersection
var x;
if (py === yStart) {
var x = values[0];
if (winding * prevWinding < 0) {
if (x > xBefore && x < xAfter) {
++windLeft;
++windRight;
} else if (x < xBefore) {
x = values[0];
} else if (py === yEnd) {
x = values[6];
} else if (Curve.solveCubic(values, 1, py, roots, 0, 1) === 1) {
x = Curve.getPoint(values, roots[0]).x;
}
if (x != null) {
// count the intersection of the ray with the monotonic curve if
// - the crossing is not at the start of the curve
// - or the windings are opposite (intersect at a vertical extremum)
// - or the start of the current curve and the end of the prev
// curve are on opposite sides of px
var isWindingChange = winding === -prevWinding,
countIntersection = py !== yStart || isWindingChange ||
(x - px) * (prevXEnd - px) < 0;
if (countIntersection) {
if (x < xBefore) {
windLeft += winding;
} else if (x > xAfter) {
windRight += winding;
} else if (py === yStart && isWindingChange) {
// intersection is at a vertical extremum
++windLeft;
++windRight;
}
} else if (x < xBefore && prevEnd > xBefore) {
windLeft += winding;
} else if (x > xAfter && prevEnd < xAfter) {
windRight += winding;
}
} else if (Curve.solveCubic(values, 1, py, roots, 0, 1)
=== 1) {
var x = Curve.getPoint(values, roots[0]).x;
if (x < xBefore) {
windLeft += winding;
} else if (x > xAfter) {
windRight += winding;
}
}
// Update previous winding and end coordinate whenever
// we encountered a non-horizontal curve.
// the ray intersects a non-horizontal curve.
prevWinding = winding;
prevEnd = values[6];
prevXEnd = values[6];
}
}
}