scratchfoundation/paper.js
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Fix issue with imprecise tangents / normals to curves at t = 0, 1.

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Jürg Lehni 2013-04-20 17:40:19 -07:00
parent 1952e3dc7d
commit 461def5383
1 changed files with 13 additions and 11 deletions
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24
src/path/Curve.js
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@ -437,13 +437,6 @@ statics: {
x = t === 0 ? p1x : p2x; x = t === 0 ? p1x : p2x;
y = t === 0 ? p1y : p2y; y = t === 0 ? p1y : p2y;
} else { } else {
// TODO: Find a better solution for this:
// Prevent tangents and normals of length 0:
var tMin = /*#=*/ Numerical.TOLERANCE;
if (t < tMin && c1x == p1x && c1y == p1y)
t = tMin;
else if (t > 1 - tMin && c2x == p2x && c2y == p2y)
t = 1 - tMin;
// Calculate the polynomial coefficients. // Calculate the polynomial coefficients.
var cx = 3 * (c1x - p1x), var cx = 3 * (c1x - p1x),
bx = 3 * (c2x - c1x) - cx, bx = 3 * (c2x - c1x) - cx,
@ -460,10 +453,19 @@ statics: {
break; break;
case 1: // tangent, 1st derivative case 1: // tangent, 1st derivative
case 2: // normal, 1st derivative case 2: // normal, 1st derivative
// Simply use the derivation of the bezier function for both // Prevent tangents and normals of length 0:
// the x and y coordinates: // http://stackoverflow.com/questions/10506868/
x = (3 * ax * t + 2 * bx) * t + cx; var tMin = /*#=*/ Numerical.TOLERANCE;
y = (3 * ay * t + 2 * by) * t + cy; if (t < tMin && c1x == p1x && c1y == p1y
|| t > 1 - tMin && c2x == p2x && c2y == p2y) {
x = c2x - c1x;
y = c2y - c1y;
} else {
// Simply use the derivation of the bezier function for both
// the x and y coordinates:
x = (3 * ax * t + 2 * bx) * t + cx;
y = (3 * ay * t + 2 * by) * t + cy;
}
break; break;
case 3: // curvature, 2nd derivative case 3: // curvature, 2nd derivative
x = 6 * ax * t + 2 * bx; x = 6 * ax * t + 2 * bx;