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[PD] rewrite a Helix function

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rewrite the function to check if helix might intersect itself to make it better readable/understandable
This commit is contained in:
Uwe
2021-12-05 21:28:52 +01:00
parent 1af3755a17
commit d2dc6ca7dd
1 changed files with 21 additions and 20 deletions
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41
src/Mod/PartDesign/App/FeatureHelix.cpp
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@@ -471,35 +471,36 @@ TopoDS_Shape Helix::generateHelixPath(void)
// this function calculates self intersection safe pitch based on the profile bounding box.
double Helix::safePitch()
{
Base::Vector3d v = Axis.getValue();
Base::Vector3d n = getProfileNormal();
Base::Vector3d s = v.Cross(n); // pointing towards the desired helix start point.
if (s.IsNull())
return Precision::Confusion(); // if the axis orthogonal to the profile, any pitch >0 is safe
// Below is an approximation. It is possible to do the general way by solving for the pitch
// where the helix is self intersecting.
Base::Vector3d axis = Axis.getValue();
Base::Vector3d start = axis.Cross(getProfileNormal()); // pointing towards the helix start point
if (start.IsNull())
return Precision::Confusion(); // if the axis orthogonal to the profile, any pitch > 0 is safe
double angle = Angle.getValue() / 180.0 * M_PI;
gp_Dir direction(axis.x, axis.y, axis.z);
gp_Dir directionStart(start.x, start.y, start.z);
TopoDS_Shape sketchshape = getVerifiedFace();
Bnd_Box bb;
BRepBndLib::Add(sketchshape, bb);
Bnd_Box boundingBox;
BRepBndLib::Add(sketchshape, boundingBox);
// get boundary and dimensions of boundingBox
double Xmin, Ymin, Zmin, Xmax, Ymax, Zmax;
bb.Get(Xmin, Ymin, Zmin, Xmax, Ymax, Zmax);
boundingBox.Get(Xmin, Ymin, Zmin, Xmax, Ymax, Zmax);
double X = Xmax - Xmin, Y = Ymax - Ymin, Z = Zmax - Zmin;
gp_Vec boundingBoxVector(X, Y, Z);
gp_Dir dir(v.x, v.y, v.z);
gp_Vec bbvec(X, Y, Z);
// Below is an approximation becaue since we take the bounding box it is
// impossible to calculate it precisely. For example a circle has as bounding
// box a square and thus results in a larger pitch than really necessary
double p0 = bbvec * dir; // safe pitch if angle=0
// minimal safe pitch if the angle is 0
double p0 = boundingBoxVector * direction;
gp_Dir dir_s(s.x, s.y, s.z);
if (tan(abs(angle)) * p0 > abs(bbvec * dir_s))
return abs(bbvec * dir_s) / tan(abs(angle));
// if the angle is so large that the distange perpendicular to p0
// between two turns is larger than the bounding box size in this direction
// the pitch can be smaller than p0
if (tan(abs(angle)) * p0 > abs(boundingBoxVector * directionStart))
return abs(boundingBoxVector * directionStart) / tan(abs(angle));
else
return p0;
}