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Improve evaluation of tangents and normals at t == 0 and 1.

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This commit is contained in:
Jürg Lehni 2014-02-19 18:50:30 +01:00
parent 1a0eead28c
commit cc0f088a11
1 changed files with 12 additions and 5 deletions
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17
src/path/Curve.js
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@ -485,12 +485,14 @@ statics: {
c1x = v[2], c1y = v[3],
c2x = v[4], c2y = v[5],
p2x = v[6], p2y = v[7],
tolerance = /*#=*/ Numerical.TOLERANCE,
x, y;
// Handle special case at beginning / end of curve
if (type === 0 && (t === 0 || t === 1)) {
x = t === 0 ? p1x : p2x;
y = t === 0 ? p1y : p2y;
if (type === 0 && (t < tolerance || t > 1 - tolerance)) {
var isZero = t < tolerance;
x = isZero ? p1x : p2x;
y = isZero ? p1y : p2y;
} else {
// Calculate the polynomial coefficients.
var cx = 3 * (c1x - p1x),
@ -510,11 +512,16 @@ statics: {
// 3: curvature, 1st derivative & 2nd derivative
// Prevent tangents and normals of length 0:
// http://stackoverflow.com/questions/10506868/
var tolerance = /*#=*/ Numerical.TOLERANCE;
if (t < tolerance && c1x === p1x && c1y === p1y
|| t > 1 - tolerance && c2x === p2x && c2y === p2y) {
x = p2x - p1x;
y = p2y - p1y;
} else if (t < tolerance) {
x = cx;
y = cy;
} else if (t > 1 - tolerance) {
x = 3 * (p2x - c2x);
y = 3 * (p2y - c2y);
} else {
// Simply use the derivation of the bezier function for both
// the x and y coordinates:
@ -532,7 +539,7 @@ statics: {
}
}
// The normal is simply the rotated tangent:
return type == 2 ? new Point(y, -x) : new Point(x, y);
return type === 2 ? new Point(y, -x) : new Point(x, y);
},
subdivide: function(v, t) {