Chris, This goes back a ways, but can you elaborate a little on what errors were fixed in the below patch? If this fixes a bug in sketch+extrude or sketch+revolve, like ray tracing or conversion, I want to make sure we properly document it.
Cheers! Sean On Jul 17, 2012, at 1:42 PM, crdu...@users.sourceforge.net wrote: > Revision: 51564 > http://brlcad.svn.sourceforge.net/brlcad/?rev=51564&view=rev > Author: crdueck > Date: 2012-07-17 17:42:16 +0000 (Tue, 17 Jul 2012) > Log Message: > ----------- > use signed curvature to find inflection point in bezier_inflection(), change > test condition for approx_bezier(), fix some errors > > Modified Paths: > -------------- > brlcad/trunk/src/librt/primitives/sketch/sketch_tess.cpp > > Modified: brlcad/trunk/src/librt/primitives/sketch/sketch_tess.cpp > =================================================================== > --- brlcad/trunk/src/librt/primitives/sketch/sketch_tess.cpp 2012-07-17 > 16:43:35 UTC (rev 51563) > +++ brlcad/trunk/src/librt/primitives/sketch/sketch_tess.cpp 2012-07-17 > 17:42:16 UTC (rev 51564) > @@ -30,10 +30,11 @@ > > #include "common.h" > > -#include <algorithm> > #include <vector> > > #include "raytrace.h" > +#include "rtgeom.h" > +#include "vmath.h" > #include "../../opennurbs_ext.h" > > > @@ -56,6 +57,7 @@ > return incenter; > } > > + > /* create a biarc for a bezier curve. > * > * extends the tangent lines to the bezier curve at its first and last control > @@ -64,7 +66,7 @@ > * of the circle defined by the first, last and intersection points. > */ > HIDDEN ON_Arc > -make_biarc(const ON_BezierCurve bezier) > +make_biarc(const ON_BezierCurve& bezier) > { > ON_2dPoint isect, arc_pt; > ON_2dPoint p_start(bezier.PointAt(0)), p_end(bezier.PointAt(1.0)); > @@ -78,22 +80,28 @@ > } > > > -/* computes the first point of inflection on a bezier if it exists by finding > - * where the magnitude of the velocity vector (1st derivative) is at a > - * maximum. > - * Returns true if an inflection point was found > +#define POW3(x) ((x)*(x)*(x)) > +#define SIGN(x) ((x) >= 0 ? 1 : -1) > +#define SIGNEDCURVATURE(d1, d2) SIGN(V2CROSS((d1), (d2)) / > POW3((d1).Length())) > + > +/* find a point of inflection on a bezier curve, if it exists, by finding the > + * value of parameter 't' where the signed curvature of the bezier changes > + * signs. Returns true if an inflection point is found. > */ > HIDDEN bool > -bezier_inflection(const ON_BezierCurve bezier, fastf_t& inflection) > +bezier_inflection(const ON_BezierCurve& bezier, fastf_t& inflection_pt) > { > fastf_t t, step = 0.1; > - for (t = 0.0; t <= 1.0; t += step) { > - ON_2dVector derv_1, derv_2; > - derv_1 = bezier.DerivativeAt(t); > - derv_2 = bezier.DerivativeAt(t + step * 0.5 > 1.0 ? 1.0 : t + step * > 0.5); > - // compare magnitude of velocity vectors > - if (derv_1.LengthSquared() > derv_2.LengthSquared()) { > - inflection = t; > + ON_3dVector d1, d2; > + ON_3dPoint tmp; > + > + bezier.Ev2Der(0, tmp, d1, d2); > + int sign = SIGNEDCURVATURE(d1, d2); > + > + for (t = step; t <= 1.0; t += step) { > + bezier.Ev2Der(t, tmp, d1, d2); > + if (sign != SIGNEDCURVATURE(d1, d2)) { > + inflection_pt = t; > return true; > } > } > @@ -107,17 +115,15 @@ > * tolerance by the biarc > */ > HIDDEN void > -approx_bezier(const ON_BezierCurve bezier, const ON_Arc biarc, const struct > bn_tol *tol, std::vector<ON_Arc>& approx) > +approx_bezier(const ON_BezierCurve& bezier, const ON_Arc& biarc, const > struct bn_tol *tol, std::vector<ON_Arc>& approx) > { > fastf_t t, step = 0.1; > fastf_t err, max_t, max_err = 0.0; > - ON_3dPoint test; > ON_BezierCurve head, tail; > > // walk the bezier curve at interval given by step > for (t = 0; t <= 1.0; t += step) { > - test = bezier.PointAt(t); > - err = (test - biarc.ClosestPointTo(test)).LengthSquared(); > + err = fabs((bezier.PointAt(t) - biarc.Center()).Length() - > biarc.Radius()); > // find the maximum point of deviation > if (err > max_err) { > max_t = t; > @@ -125,16 +131,16 @@ > } > } > > - if (max_err > tol->dist_sq) { > + if (max_err + VDIVIDE_TOL < tol->dist) { > + // bezier doesn't deviate from biarc by the given tolerance, add the > biarc > + // approximation > + approx.push_back(biarc); > + } else { > // split bezier at point of maximum deviation and recurse on the new > // subsections > bezier.Split(max_t, head, tail); > approx_bezier(head, make_biarc(head), tol, approx); > approx_bezier(tail, make_biarc(tail), tol, approx); > - } else { > - // bezier doesn't deviate from biarc by the given tolerance, add the > biarc > - // approximation > - approx.push_back(biarc); > } > } > > @@ -143,7 +149,7 @@ > * returns approximation in carcs > */ > HIDDEN void > -bezier_to_carcs(const ON_BezierCurve bezier, const struct bn_tol *tol, > std::vector<ON_Arc>& carcs) > +bezier_to_carcs(const ON_BezierCurve& bezier, const struct bn_tol *tol, > std::vector<ON_Arc>& carcs) > { > bool curvature_changed = false; > fastf_t inflection_pt, biarc_angle; > @@ -152,16 +158,14 @@ > std::vector<ON_BezierCurve> rest; > > // get inflection point, if it exists > - //if (bezier_inflection(bezier, inflection_pt)) { > - //curvature_changed = true; > - //bezier.Split(inflection_pt, current, tmp); > - //rest.push_back(tmp); > - //} else { > - //current = bezier; > - //} > + if (bezier_inflection(bezier, inflection_pt)) { > + curvature_changed = true; > + bezier.Split(inflection_pt, current, tmp); > + rest.push_back(tmp); > + } else { > + current = bezier; > + } > > - current = bezier; > - > do { > bez_to_carcs_loop: > biarc = make_biarc(current); > @@ -197,7 +201,7 @@ > > current = rest.back(); > rest.pop_back(); > - continue; > + goto loop; > } > > if (curvature_changed) { > @@ -237,8 +241,8 @@ > * else, calculate the area for the polygon edge Start->End, and the area > * of the circular segment > * bezier_seg: approximate the bezier using the bezier_to_carcs() function. > for > - * each carc_seg, calculate the area for the polygon edges Start->Mid > and > - * Mid->End, and the area of the circular segment > + * each carc_seg, calculate the area for the polygon edges Start->End > and > + * the area of the circular segment > */ > extern "C" void > rt_sketch_surf_area(fastf_t *area, const struct rt_db_internal *ip) //, const > struct bn_tol *tol) > @@ -298,9 +302,8 @@ > // approximate bezier curve by a set of circular arcs > bezier_to_carcs(ON_BezierCurve(bez_pts), &tol, carcs); > for (std::vector<ON_Arc>::iterator it = carcs.begin(); it != > carcs.end(); ++it) { > - // calculate area for polygon edges Start->Mid, Mid->End > - *area += V2CROSS(it->StartPoint(), it->MidPoint()); > - *area += V2CROSS(it->MidPoint(), it->EndPoint()); > + // calculate area for polygon edges Start->End > + *area += V2CROSS(it->StartPoint(), it->EndPoint()); > // calculate area for circular segment > *area += 0.5 * it->Radius() * it->Radius() * > (it->AngleRadians() - sin(it->AngleRadians())); > } > > This was sent by the SourceForge.net collaborative development platform, the > world's largest Open Source development site. > > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > BRL-CAD Source Commits mailing list > brlcad-comm...@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/brlcad-commits ------------------------------------------------------------------------------ Symantec Endpoint Protection 12 positioned as A LEADER in The Forrester Wave(TM): Endpoint Security, Q1 2013 and "remains a good choice" in the endpoint security space. For insight on selecting the right partner to tackle endpoint security challenges, access the full report. http://p.sf.net/sfu/symantec-dev2dev _______________________________________________ BRL-CAD Developer mailing list brlcad-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/brlcad-devel
