scratchfoundation/paper.js
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Fix imprecision in intersection code by re-introducing tolerance parameter in Curve#isFlatEnough().

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This commit is contained in:
Jürg Lehni 2012-12-27 20:13:45 +01:00
parent 3c4978eb04
commit 5b9d33f32e
2 changed files with 8 additions and 4 deletions
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8
src/path/Curve.js
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@ -544,7 +544,7 @@ statics: {
return v;
},
isFlatEnough: function(v) {
isFlatEnough: function(v, tolerance) {
// Thanks to Kaspar Fischer for the following:
// http://hcklbrrfnn.files.wordpress.com/2012/08/bez.pdf
var p1x = v[0], p1y = v[1],
@ -555,7 +555,8 @@ statics: {
uy = 3 * c1y - 2 * p1y - p2y,
vx = 3 * c2x - 2 * p2x - p1x,
vy = 3 * c2y - 2 * p2y - p1y;
return Math.max(ux * ux, vx * vx) + Math.max(uy * uy, vy * vy) < 1;
return Math.max(ux * ux, vx * vx) + Math.max(uy * uy, vy * vy)
< 16 * tolerance * tolerance;
},
getBounds: function(v) {
@ -641,7 +642,8 @@ statics: {
&& bounds1.y + bounds1.height >= bounds2.y
&& bounds1.x < bounds2.x + bounds2.width
&& bounds1.y < bounds2.y + bounds2.height) {
if (Curve.isFlatEnough(v1) && Curve.isFlatEnough(v2)) {
if (Curve.isFlatEnough(v1, /*#=*/ Numerical.TOLERANCE)
&& Curve.isFlatEnough(v2, /*#=*/ Numerical.TOLERANCE)) {
// Treat both curves as lines and see if their parametric
// equations interesct.
/*#*/ if (options.debug) {

4
src/path/PathFlattener.js
View file

@ -51,7 +51,9 @@ var PathFlattener = Base.extend({
_computeParts: function(curve, index, minT, maxT) {
// Check if the t-span is big enough for subdivision.
// We're not subdividing more than 32 times...
if ((maxT - minT) > 1 / 32 && !Curve.isFlatEnough(curve)) {
// After quite a bit of testing, a tolerance of 0.25 appears to be a
// good trade-off between speed and precision.
if ((maxT - minT) > 1 / 32 && !Curve.isFlatEnough(curve, 0.25)) {
var curves = Curve.subdivide(curve);
var halfT = (minT + maxT) / 2;
// Recursively subdive and compute parts again.