powerstroke: more robust method of determining parameters at joins. should fix some bugs. (may introduce new ones...)

(bzr r11247)

1 files changed, 18 insertions, 71 deletions

diff --git a/src/live_effects/lpe-powerstroke.cpp b/src/live_effects/lpe-powerstroke.cpp
index 281376cde..a9cf22f6a 100644
--- a/src/live_effects/lpe-powerstroke.cpp
+++ b/src/live_effects/lpe-powerstroke.cpp
@@ -205,47 +205,8 @@ static bool compare_offsets (Geom::Point first, Geom::Point second)
     return first[Geom::X] < second[Geom::X];
 }
 
-// find discontinuities in input path
-struct discontinuity_data {
-    Geom::Point der0; // unit derivative of 'left' side of join
-    Geom::Point der1; // unit derivative of 'right' side of join
-    double width; // intended stroke width at join
-};
-std::vector<discontinuity_data> find_discontinuities( Geom::Piecewise<Geom::D2<Geom::SBasis> > const & der,
-                                                      Geom::Piecewise<Geom::SBasis> const & x,
-                                                      Geom::Piecewise<Geom::SBasis> const & y,
-                                                      double eps=Geom::EPSILON )
-{
-    std::vector<discontinuity_data> vect;
-    for(unsigned i = 1; i < der.size(); i++) {
-        if ( ! are_near(der[i-1].at1(), der[i].at0(), eps) ) {
-            discontinuity_data data;
-
-            data.der0 = der[i-1].at1();
-            data.der1 = der[i].at0();
-            if ( Geom::are_near(data.der0.length(), 0) ) {
-                data.der0 = -unitTangentAt(reverse(der[i-1]),0.,2); // == unitTangentAt(der[i-1], 1, 2);
-            }
-            if ( Geom::are_near(data.der1.length(), 0) ) {
-                data.der1 = unitTangentAt(der[i], 0, 2);
-            }
-
-            double t = der.cuts[i];
-            std::vector< double > rts = roots (x - t);  /// @todo this has multiple solutions for general strokewidth paths (generated by spiro interpolator...), ignore for now
-            if (!rts.empty()) {
-                data.width = y(rts.front());
-            } else {
-                data.width = 1;
-            }
-            vect.push_back(data);
-        }
-    }
-    return vect;
-}
-
-
 Geom::Path path_from_piecewise_fix_cusps( Geom::Piecewise<Geom::D2<Geom::SBasis> > const & B,
-                                          std::vector<discontinuity_data> const & cusps,
+                                          Geom::Piecewise<Geom::SBasis> const & y, // width path
                                           LineJoinType jointype,
                                           double miter_limit,
                                           bool forward_direction,
@@ -258,9 +219,6 @@ Geom::Path path_from_piecewise_fix_cusps( Geom::Piecewise<Geom::D2<Geom::SBasis>
         return pb.peek().front();
     }
 
-    double sign = forward_direction ? 1. : -1.;
-
-    unsigned int cusp_i = forward_direction ? 0 : cusps.size()-1;
     Geom::Point start = B[0].at0();
     pb.moveTo(start);
     build_from_sbasis(pb, B[0], tol, false);
@@ -273,9 +231,12 @@ Geom::Path path_from_piecewise_fix_cusps( Geom::Piecewise<Geom::D2<Geom::SBasis>
         }
         if (!are_near(B[prev_i].at1(), B[i].at0(), tol) )
         { // discontinuity found, so fix it :-)
-            discontinuity_data cusp = cusps[cusp_i];
+            double width = y( B.cuts[i] );
 
-            bool on_outside = ( sign*cusp.width*angle_between(cusp.der0, cusp.der1) < 0. );
+            Geom::Point tang1 = -unitTangentAt(reverse(B[prev_i]),0.); // = unitTangentAt(B[prev_i],1);
+            Geom::Point tang2 = unitTangentAt(B[i],0);
+            Geom::Point discontinuity_vec = B[i].at0() - B[prev_i].at1();
+            bool on_outside = ( dot(tang1, discontinuity_vec) >= 0. );
 
             switch (jointype) {
             case LINEJOIN_ROUND: {
@@ -289,8 +250,6 @@ Geom::Path path_from_piecewise_fix_cusps( Geom::Piecewise<Geom::D2<Geom::SBasis>
                        A 2Geom method was created to do exactly this :)
                        */
 
-                    Geom::Point tang1 = -unitTangentAt(reverse(B[prev_i]),0.); // = unitTangentAt(B[prev_i],1);
-                    Geom::Point tang2 = unitTangentAt(B[i],0);
                     boost::optional<Geom::Point> O = intersection_point( B[prev_i].at1(), tang1,
                                                                               B[i].at0(), tang2 );
                     if (!O) {
@@ -301,7 +260,7 @@ Geom::Path path_from_piecewise_fix_cusps( Geom::Piecewise<Geom::D2<Geom::SBasis>
 
                     Geom::Ellipse ellipse = find_ellipse(B[prev_i].at1(), B[i].at0(), *O);
                     pb.arcTo( ellipse.ray(Geom::X), ellipse.ray(Geom::Y), ellipse.rot_angle(),
-                              false, cusp.width < 0, B[i].at0() );
+                              false, width < 0, B[i].at0() );
                 } else {
                     // we are on the inside, do a simple bevel to connect the paths
                     pb.lineTo(B[i].at0()); // default to bevel for too shallow cusp angles
@@ -311,8 +270,7 @@ Geom::Path path_from_piecewise_fix_cusps( Geom::Piecewise<Geom::D2<Geom::SBasis>
 /*            case LINEJOIN_NONE: {
                 if ( on_outside ) {
                     // we are on the outside
-                    Geom::Point der1 = -unitTangentAt(reverse(B[prev_i]),0.); // = unitTangentAt(B[prev_i],1);
-                    Geom::Point point_on_path = B[prev_i].at1() - rot90(der1) * cusp.width;
+                    Geom::Point point_on_path = B[prev_i].at1() - rot90(tang1) * width;
                     pb.lineTo(point_on_path);
                     pb.lineTo(B[i].at0());
                 } else {
@@ -324,13 +282,10 @@ Geom::Path path_from_piecewise_fix_cusps( Geom::Piecewise<Geom::D2<Geom::SBasis>
                 if (on_outside) {
                     // we are on the outside, do something complicated to make it look good ;)
 
-                    Geom::Point der1 = -unitTangentAt(reverse(B[prev_i]),0.); // = unitTangentAt(B[prev_i],1);
-                    Geom::Point der2 = unitTangentAt(B[i],0);
-
-                    Geom::D2<Geom::SBasis> newcurve1 = B[prev_i] * Geom::reflection(rot90(der1), B[prev_i].at1());
+                    Geom::D2<Geom::SBasis> newcurve1 = B[prev_i] * Geom::reflection(rot90(tang1), B[prev_i].at1());
                     Geom::CubicBezier bzr1 = sbasis_to_cubicbezier( reverse(newcurve1) );
 
-                    Geom::D2<Geom::SBasis> newcurve2 = B[i] * Geom::reflection(rot90(der2), B[i].at0());
+                    Geom::D2<Geom::SBasis> newcurve2 = B[i] * Geom::reflection(rot90(tang2), B[i].at0());
                     Geom::CubicBezier bzr2 = sbasis_to_cubicbezier( reverse(newcurve2) );
 
                     Geom::Crossings cross = crossings(bzr1, bzr2);
@@ -339,9 +294,9 @@ Geom::Path path_from_piecewise_fix_cusps( Geom::Piecewise<Geom::D2<Geom::SBasis>
                         pb.lineTo(B[i].at0());
                     } else {
                         // check size of miter
-                        Geom::Point point_on_path = B[prev_i].at1() - rot90(der1) * cusp.width;
+                        Geom::Point point_on_path = B[prev_i].at1() - rot90(tang1) * width;
                         Geom::Coord len = distance(bzr1.pointAt(cross[0].ta), point_on_path);
-                        if (len > fabs(cusp.width) * miter_limit) {
+                        if (len > fabs(width) * miter_limit) {
                             // miter too big: default to bevel
                             pb.lineTo(B[i].at0());
                         } else {
@@ -362,15 +317,13 @@ Geom::Path path_from_piecewise_fix_cusps( Geom::Piecewise<Geom::D2<Geom::SBasis>
                 if (on_outside) {
                     // we are on the outside, do something complicated to make it look good ;)
 
-                    Geom::Point der1 = -unitTangentAt(reverse(B[prev_i]),0.); // = unitTangentAt(B[prev_i],1);
-                    Geom::Point der2 = unitTangentAt(B[i],0);
-                    boost::optional<Geom::Point> p = intersection_point( B[prev_i].at1(), der1,
-                                                                         B[i].at0(), der2 );
+                    boost::optional<Geom::Point> p = intersection_point( B[prev_i].at1(), tang1,
+                                                                         B[i].at0(), tang2 );
                     if (p) {
                         // check size of miter
-                        Geom::Point point_on_path = B[prev_i].at1() - rot90(der1) * cusp.width;
+                        Geom::Point point_on_path = B[prev_i].at1() - rot90(tang1) * width;
                         Geom::Coord len = distance(*p, point_on_path);
-                        if (len <= fabs(cusp.width) * miter_limit) {
+                        if (len <= fabs(width) * miter_limit) {
                             // miter OK
                             pb.lineTo(*p);
                         }
@@ -384,9 +337,6 @@ Geom::Path path_from_piecewise_fix_cusps( Geom::Piecewise<Geom::D2<Geom::SBasis>
             }
             case LINEJOIN_SPIRO: {
                 if (on_outside) {
-                    Geom::Point tang1 = -unitTangentAt(reverse(B[prev_i]),0.); // = unitTangentAt(B[prev_i],1);
-                    Geom::Point tang2 = unitTangentAt(B[i],0);
-
                     Geom::Point direction = B[i].at0() - B[prev_i].at1();
                     double tang1_sign = dot(direction,tang1);
                     double tang2_sign = dot(direction,tang2);
@@ -419,8 +369,6 @@ Geom::Path path_from_piecewise_fix_cusps( Geom::Piecewise<Geom::D2<Geom::SBasis>
                 pb.lineTo(B[i].at0());
                 break;
             }
-
-            cusp_i += forward_direction ? 1 : -1;
         }
         build_from_sbasis(pb, B[i], tol, false);
         prev_i = i;
@@ -491,14 +439,13 @@ LPEPowerStroke::doEffect_path (std::vector<Geom::Path> const & path_in)
         y = portion(y, rtsmin.at(0), rtsmax.at(0));
     }
 
-    std::vector<discontinuity_data> cusps = find_discontinuities(der, x, y);
     LineJoinType jointype = static_cast<LineJoinType>(linejoin_type.get_value());
 
     Piecewise<D2<SBasis> > pwd2_out   = compose(pwd2_in,x) + y*compose(n,x);
     Piecewise<D2<SBasis> > mirrorpath = reverse(compose(pwd2_in,x) - y*compose(n,x));
 
-    Geom::Path fixed_path       = path_from_piecewise_fix_cusps( pwd2_out,   cusps, jointype, miter_limit, true, LPE_CONVERSION_TOLERANCE);
-    Geom::Path fixed_mirrorpath = path_from_piecewise_fix_cusps( mirrorpath, cusps, jointype, miter_limit, false, LPE_CONVERSION_TOLERANCE);
+    Geom::Path fixed_path       = path_from_piecewise_fix_cusps( pwd2_out,   y, jointype, miter_limit, LPE_CONVERSION_TOLERANCE);
+    Geom::Path fixed_mirrorpath = path_from_piecewise_fix_cusps( mirrorpath, reverse(y), jointype, miter_limit, LPE_CONVERSION_TOLERANCE);
 
     if (path_in[0].closed()) {
         fixed_path.close(true);