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Sketcher: Correction of B spline normals

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When writting solver implementations it has to be taken into account that the normal is not to be provided in the sense of the curvature, but to
the left when walking a curve from start to end.

https://forum.freecadweb.org/viewtopic.php?f=10&t=26312#p209486

This commit has impact on all the previous files using bspline and endpoint to endpoint tangency.

A work-around is to delete the tangency and do it again.
This commit is contained in:
Abdullah Tahiri
2018-01-14 15:58:45 +01:00
committed by wmayer
parent fd7d75b309
commit 4bfa12d86d
1 changed files with 8 additions and 14 deletions
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22
src/Mod/Sketcher/App/planegcs/Geo.cpp
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@@ -613,6 +613,12 @@ DeriVector2 BSpline::CalculateNormal(Point& p, double* derivparam)
// place holder
DeriVector2 ret;
// even if this method is call CalculateNormal, the returned vector is not the normal strictu sensus
// but a normal vector, where the vector should point to the left when one walks along the curve from
// start to end.
//
// https://forum.freecadweb.org/viewtopic.php?f=10&t=26312#p209486
if (mult[0] > degree && mult[mult.size()-1] > degree) {
// if endpoints through end poles
if(*p.x == *start.x && *p.y == *start.y) {
@@ -620,30 +626,18 @@ DeriVector2 BSpline::CalculateNormal(Point& p, double* derivparam)
// then tangency is defined by first to second poles
DeriVector2 endpt(this->poles[1], derivparam);
DeriVector2 spt(this->poles[0], derivparam);
DeriVector2 npt(this->poles[2], derivparam); // next pole to decide normal direction
DeriVector2 tg = endpt.subtr(spt);
DeriVector2 nv = npt.subtr(spt);
if ( tg.scalarProd(nv) > 0 )
ret = tg.rotate90cw();
else
ret = tg.rotate90ccw();
ret = tg.rotate90ccw();
}
else if(*p.x == *end.x && *p.y == *end.y) {
// and you are asking about the normal at end point
// then tangency is defined by last to last but one poles
DeriVector2 endpt(this->poles[poles.size()-1], derivparam);
DeriVector2 spt(this->poles[poles.size()-2], derivparam);
DeriVector2 npt(this->poles[poles.size()-3], derivparam); // next pole to decide normal direction
DeriVector2 tg = endpt.subtr(spt);
DeriVector2 nv = npt.subtr(spt);
if ( tg.scalarProd(nv) > 0 )
ret = tg.rotate90ccw();
else
ret = tg.rotate90cw();
ret = tg.rotate90ccw();
} else {
// another point and we have no clue until we implement De Boor
ret = DeriVector2();