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Sketcher: Symmetric arc when center is on symmetry line. (#24228)

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* Sketcher: Symmetric arc when center is on symmetry line.

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This commit is contained in:
PaddleStroke
2025-10-06 18:02:42 +02:00
committed by GitHub
parent 85776dd66b
commit 365af33fc6
1 changed files with 54 additions and 0 deletions
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54
src/Mod/Sketcher/App/Sketch.cpp
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@@ -3726,6 +3726,60 @@ int Sketch::addSymmetricConstraint(int geoId1, PointPos pos1, int geoId2, PointP
return -1;
}
// Special handling for arc endpoint symmetry when the arc's center is on the symmetry axis.
// In this specific geometric configuration, the perpendicularity part of the symmetry
// constraint is inherently redundant. Applying it would lead to solver errors.
// We detect this case and add only the midpoint-on-line part of the constraint,
// which is sufficient to enforce symmetry without causing redundancy.
// Step 1: Check if the two points (p1, p2) are endpoints of the same arc.
// We iterate through all geometries to find an arc whose start/end points match our input
// points.
int arcGeoId = -1;
for (int i = 0; i < (int)Geoms.size(); ++i) {
if (Geoms[i].type == Arc) {
int arcStartPointId = Geoms[i].startPointId;
int arcEndPointId = Geoms[i].endPointId;
int p1_Id = getPointId(geoId1, pos1);
int p2_Id = getPointId(geoId2, pos2);
if ((p1_Id == arcStartPointId && p2_Id == arcEndPointId)
|| (p1_Id == arcEndPointId && p2_Id == arcStartPointId)) {
arcGeoId = i;
break;
}
}
}
if (arcGeoId != -1) {
// Step 2: We found the arc. Now check if its center lies on the symmetry line.
int centerPointId = Geoms[arcGeoId].midPointId;
GCS::Point& center = Points[centerPointId];
GCS::Line& l = Lines[Geoms[geoId3].index]; // The symmetry line
double dx = *l.p2.x - *l.p1.x;
double dy = *l.p2.y - *l.p1.y;
double line_len_sq = dx * dx + dy * dy;
if (line_len_sq > Precision::SquareConfusion()) {
double area = (*center.x - *l.p1.x) * dy - (*center.y - *l.p1.y) * dx;
if (std::abs(area) / sqrt(line_len_sq) < Precision::Confusion()) {
// The center IS on the symmetry line. This is the degenerate case.
// Weaken the constraint by only adding the midpoint part.
int pointId1 = getPointId(geoId1, pos1);
int pointId2 = getPointId(geoId2, pos2);
GCS::Point& p1 = Points[pointId1];
GCS::Point& p2 = Points[pointId2];
int tag = ++ConstraintsCounter;
// addConstraintMidpointOnLine is a GCS::System method, but we can call it from
// here.
GCSsys.addConstraintMidpointOnLine(p1, p2, l.p1, l.p2, tag);
return ConstraintsCounter;
}
}
}
int pointId1 = getPointId(geoId1, pos1);
int pointId2 = getPointId(geoId2, pos2);