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Cubic curve distance optimization

This commit is contained in:
Chlumsky 2025-06-20 16:50:26 +02:00
parent 9e7901aa7c
commit e3ced1e362
1 changed files with 14 additions and 9 deletions
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23
core/edge-segments.cpp
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@ -244,17 +244,22 @@ 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;
double t = 1./MSDFGEN_CUBIC_SEARCH_STARTS*i;
Vector2 qe = qa+3*t*ab+3*t*t*br+t*t*t*as;
Vector2 d1 = 3*ab+6*t*br+3*t*t*as;
for (int step = 0; step < MSDFGEN_CUBIC_SEARCH_STEPS; ++step) {
// Improve t
Vector2 d2 = 6*br+6*t*as;
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;
d1 = 3*ab+6*t*br+3*t*t*as;
Vector2 d2 = 6*br+6*t*as;
double improvedT = t-dotProduct(qe, d1)/(dotProduct(d1, d1)+dotProduct(qe, d2));
if (improvedT > 0 && improvedT < 1) {
int remainingSteps = MSDFGEN_CUBIC_SEARCH_STEPS;
do {
t = improvedT;
qe = qa+3*t*ab+3*t*t*br+t*t*t*as;
d1 = 3*ab+6*t*br+3*t*t*as;
if (!--remainingSteps)
break;
d2 = 6*br+6*t*as;
improvedT = t-dotProduct(qe, d1)/(dotProduct(d1, d1)+dotProduct(qe, d2));
} while (improvedT > 0 && improvedT < 1);
double distance = qe.length();
if (distance < fabs(minDistance)) {
minDistance = nonZeroSign(crossProduct(d1, qe))*distance;