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Fixed an edge case in cubic curve distance evaluation

This commit is contained in:
Viktor Chlumský 2020-10-11 15:37:44 +02:00
parent 17ea97c085
commit 8c6fb790b5
1 changed files with 9 additions and 10 deletions
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19
core/edge-segments.cpp
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@ -172,21 +172,20 @@ SignedDistance CubicSegment::signedDistance(Point2 origin, double &param) const
// Iterative minimum distance search
for (int i = 0; i <= MSDFGEN_CUBIC_SEARCH_STARTS; ++i) {
double t = (double) i/MSDFGEN_CUBIC_SEARCH_STARTS;
for (int step = 0;; ++step) {
Vector2 qe = p[0]+3*t*ab+3*t*t*br+t*t*t*as-origin; // do not simplify with qa !!!
Vector2 qe = qa+3*t*ab+3*t*t*br+t*t*t*as;
for (int step = 0; step < MSDFGEN_CUBIC_SEARCH_STEPS; ++step) {
// Improve t
Vector2 d1 = 3*as*t*t+6*br*t+3*ab;
Vector2 d2 = 6*as*t+6*br;
t -= dotProduct(qe, d1)/(dotProduct(d1, d1)+dotProduct(qe, d2));
if (t <= 0 || t >= 1)
break;
qe = qa+3*t*ab+3*t*t*br+t*t*t*as;
double distance = nonZeroSign(crossProduct(direction(t), qe))*qe.length();
if (fabs(distance) < fabs(minDistance)) {
minDistance = distance;
param = t;
}
if (step == MSDFGEN_CUBIC_SEARCH_STEPS)
break;
// Improve t
Vector2 d1 = 3*as*t*t+6*br*t+3*ab;
Vector2 d2 = 6*as*t+6*br;
t -= dotProduct(qe, d1)/(dotProduct(d1, d1)+dotProduct(qe, d2));
if (t < 0 || t > 1)
break;
}
}