Revision: 56000
http://sourceforge.net/p/brlcad/code/56000
Author: phoenixyjll
Date: 2013-07-11 07:58:18 +0000 (Thu, 11 Jul 2013)
Log Message:
-----------
Add arc (including circle) fitting and ellipse (including elliptical arc)
fitting.
Modified Paths:
--------------
brlcad/trunk/src/libbrep/intersect.cpp
Modified: brlcad/trunk/src/libbrep/intersect.cpp
===================================================================
--- brlcad/trunk/src/libbrep/intersect.cpp 2013-07-11 03:20:08 UTC (rev
55999)
+++ brlcad/trunk/src/libbrep/intersect.cpp 2013-07-11 07:58:18 UTC (rev
56000)
@@ -1851,9 +1851,12 @@
ON_Curve*
curve_fitting(ON_Curve* in, double fitting_tolerance, bool delete_curve =
false)
{
+ // Fit a *2D* curve into line, arc, ellipse or other comic curves.
+
if (in == NULL)
return NULL;
+ // Linear fitting
if (in->IsLinear(fitting_tolerance)) {
ON_LineCurve *linecurve = new ON_LineCurve(in->PointAtStart(),
in->PointAtEnd());
linecurve->ChangeDimension(in->Dimension());
@@ -1861,6 +1864,79 @@
return linecurve;
}
+ // Arc fitting (including circle)
+ ON_Arc arc;
+ if (in->IsArc(&ON_xy_plane, &arc, fitting_tolerance)) {
+ if (delete_curve) delete in;
+ ON_ArcCurve* arccurve = new ON_ArcCurve(arc);
+ arccurve->ChangeDimension(in->Dimension());
+ return arccurve;
+ }
+
+ double conic[6];
+ double sample_pts[12];
+ int plotres = in->IsClosed() ? 6 : 5;
+ for (int i = 0; i < 6; i++) {
+ ON_3dPoint pt3d =
in->PointAt(in->Domain().ParameterAt((double)i/plotres));
+ sample_pts[2*i] = pt3d.x;
+ sample_pts[2*i+1] = pt3d.y;
+ }
+ if (ON_GetConicEquationThrough6Points(2, sample_pts, conic, NULL, NULL,
NULL)) {
+ // It may be a conic.
+ ON_2dPoint ell_center;
+ ON_2dVector ell_A, ell_B;
+ double ell_a, ell_b;
+ // First, fitting an ellipse. It seems that ON_Curve::IsEllipse()
+ // doesn't work, so we use conic fitting first. If this is not ideal,
+ // an alternative solution is to use least square fitting on all
+ // points.
+ if (ON_IsConicEquationAnEllipse(conic, ell_center, ell_A, ell_B,
&ell_a, &ell_b)) {
+ ON_Plane ell_plane = ON_Plane(ON_3dPoint(ell_center),
ON_3dVector(ell_A), ON_3dVector(ell_B));
+ ON_Ellipse ell(ell_plane, ell_a, ell_b);
+ int knotcnt = in->SpanCount();
+ double* knots = new double [knotcnt + 1];
+ in->GetSpanVector(knots);
+ int i;
+ double t_min = DBL_MAX, t_max = -DBL_MAX;
+ for (i = 0; i <= knotcnt; i++) {
+ // It may not be a complete ellipse.
+ // We find the domain of its parameter.
+ ON_3dPoint pt = in->PointAt(knots[i]);
+ double t;
+ ON_3dPoint ell_pt;
+ if (!ell.ClosestPointTo(pt, &t))
+ break;
+ ell_pt = ell.PointAt(t);
+ if (ell_pt.DistanceTo(pt) > fitting_tolerance)
+ break;
+ t_min = std::min(t, t_min);
+ t_max = std::max(t, t_max);
+ }
+ if (i == knotcnt+1) {
+ // All points are on the ellipse
+ if (in->IsClosed()) {
+ t_max = ON_PI*2, t_min = 0;
+ }
+ ON_NurbsCurve nurbscurve;
+ ell.GetNurbForm(nurbscurve);
+ // The params of the nurbscurve is between [0, 2*pi]
+ ON_Curve *left = NULL, *right = NULL;
+ if (!ON_NearZero(t_min))
+ nurbscurve.Split(t_min, left, right);
+ else
+ right = &nurbscurve;
+ if (right && !ON_NearZero(t_max - 2*ON_PI))
+ right->Split(t_max, left, right);
+ else
+ left = right;
+ if (delete_curve) delete in;
+ return left->Duplicate();
+ }
+ }
+ }
+
+ // We have tried all fittings, but none of them succeed.
+ // So we just return the original curve.
return in;
}
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