scratchfoundation/paper.js
1
0
Fork 0
mirror of https://github.com/scratchfoundation/paper.js.git synced 2025-01-20 22:39:50 -05:00
Code Issues Projects Releases Packages Wiki Activity Actions

Winding number calculation for a given point

Browse source
This commit is contained in:
hkrish 2013-12-25 20:46:13 +01:00
parent 39c52f326e
commit 4562b104f2
1 changed files with 61 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

61
src/path/PathItem.js
View file

@ -190,6 +190,67 @@ var PathItem = Item.extend(/** @lends PathItem# */{
return !(this.hasFill() && this.hasStroke());
},
/**
* Returns the winding contribution of the given point with respect to this
* PathItem.
*/
_getWinding: function(point, isHorizontal) {
var v,
curves = this._getMonotoneCurves(),
tolerance = /*#=*/ Numerical.TOLERANCE;
var i, li, t, x0, ty, wind,
tolMin = -tolerance,
tolMax = 1 + -tolerance,
xAfter = point.x + tolerance,
xBefore = point.x - tolerance,
tMin = tolMin,
tMax = tolerance,
tVal = 0,
y = point.y,
winding = 0,
roots = [];
// Adjustment for horizontal curve. Here, we will miss to count
// atleast one intercept since we only account for y intercepts
// on other curves excluding the end point of those curves.
if (isHorizontal){
tolMin = tolerance;
tolMax = 1 + tolerance;
tMin = 1 - tolerance;
tMax = tolMax;
tVal = 1;
}
// DEBUG:
var check = point.x === 217.32504322936848 && point.y === 354.67997242479777;
// Find the winding number for right hand side of the curve,
// inclusive of the curve itself, while tracing along its direction.
for (i = 0, li = curves.length; i < li; i++) {
v = curves[i];
if (Curve.solveCubic(v, 1, y, roots, tolMin, tolMax) === 1) {
t = roots[0];
if ( t >= tMin && t <= tMax)
t = tVal;
x0 = Curve.evaluate(v, t, 0).x;
ty = Curve.evaluate(v, t, 1).y;
// DEBUG:
// wind = v[8];
// if (check && (x0 >= xAfter || (x0 >= xBefore && wind > 0))){
// hilightCrv(v);
// markPoint(Curve.evaluate(v, 0.5, 0), t.toFixed(1), null, 0.01);
// // markPoint(new paper.Point(x0, y), t.toFixed(1), null, 0.001);
// console.log(t.toFixed(1), ty, v[8]);
// }
wind = v[8];
if (x0 >= xAfter){
winding += wind;
} else if (x0 >= xBefore && wind > 0) {
winding += wind;
}
}
}
return Math.abs(winding);
},
_contains: function(point) {
// NOTE: point is reverse transformed by _matrix, so we don't need to
// apply here.