1 files changed, 194 insertions, 0 deletions
diff --git a/src/live_effects/lpe-extrude.cpp b/src/live_effects/lpe-extrude.cpp
new file mode 100644
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+++ b/src/live_effects/lpe-extrude.cpp
@@ -0,0 +1,194 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/**
+ * @file
+ * LPE effect for extruding paths (making them "3D").
+ *
+ */
+/* Authors:
+ *   Johan Engelen <j.b.c.engelen@utwente.nl>
+ *
+ * Copyright (C) 2009 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include "live_effects/lpe-extrude.h"
+
+// TODO due to internal breakage in glibmm headers, this must be last:
+#include <glibmm/i18n.h>
+
+
+namespace Inkscape {
+namespace LivePathEffect {
+
+LPEExtrude::LPEExtrude(LivePathEffectObject *lpeobject) :
+    Effect(lpeobject),
+    extrude_vector(_("Direction"), _("Defines the direction and magnitude of the extrusion"), "extrude_vector", &wr, this, Geom::Point(-10,10))
+{
+    show_orig_path = true;
+    concatenate_before_pwd2 = false;
+
+    registerParameter(&extrude_vector);
+}
+
+LPEExtrude::~LPEExtrude()
+= default;
+
+static bool are_colinear(Geom::Point a, Geom::Point b) {
+    return Geom::are_near(cross(a,b), 0., 0.5);
+}
+
+// find cusps, except at start/end for closed paths.
+// this should be factored out later.
+static std::vector<double> find_cusps( Geom::Piecewise<Geom::D2<Geom::SBasis> > const & pwd2_in ) {
+    using namespace Geom;
+    Piecewise<D2<SBasis> > deriv = derivative(pwd2_in);
+    std::vector<double> cusps;
+    // cusps are spots where the derivative jumps.
+    for (unsigned i = 1 ; i < deriv.size() ; ++i) {
+        if ( ! are_colinear(deriv[i-1].at1(), deriv[i].at0()) ) {
+            // there is a jump in the derivative, so add it to the cusps list
+            cusps.push_back(deriv.cuts[i]);
+        }
+    }
+    return cusps;
+}
+
+Geom::Piecewise<Geom::D2<Geom::SBasis> >
+LPEExtrude::doEffect_pwd2 (Geom::Piecewise<Geom::D2<Geom::SBasis> > const & pwd2_in)
+{
+    using namespace Geom;
+
+    // generate connecting lines (the 'sides' of the extrusion)
+    Geom::Path path(Point(0.,0.));
+    path.appendNew<Geom::LineSegment>( extrude_vector.getVector() );
+    Piecewise<D2<SBasis> > connector = path.toPwSb();
+
+    switch( 1 ) {
+    case 0: {
+        /* This one results in the following subpaths: the original, a displaced copy, and connector lines between the two
+         */
+
+        Piecewise<D2<SBasis> > pwd2_out = pwd2_in;
+        // generate extrusion bottom: (just a copy of original path, displaced a bit)
+        pwd2_out.concat( pwd2_in + extrude_vector.getVector() );
+
+        // connecting lines should be put at start and end of path if it is not closed
+        // it is not possible to check whether a piecewise<T> path is closed, 
+        // so we check whether start and end are close
+        if ( ! are_near(pwd2_in.firstValue(), pwd2_in.lastValue()) ) {
+            pwd2_out.concat( connector + pwd2_in.firstValue() );
+            pwd2_out.concat( connector + pwd2_in.lastValue() );
+        }
+        // connecting lines should be put at cusps
+        Piecewise<D2<SBasis> > deriv = derivative(pwd2_in);
+        std::vector<double> cusps; // = roots(deriv);
+        for (double cusp : cusps) {
+            pwd2_out.concat( connector + pwd2_in.valueAt(cusp) );
+        }
+        // connecting lines should be put where the tangent of the path equals the extrude_vector in direction
+        std::vector<double> rts = roots(dot(deriv, rot90(extrude_vector.getVector())));
+        for (double rt : rts) {
+            pwd2_out.concat( connector + pwd2_in.valueAt(rt) );
+        }
+        return pwd2_out;
+    }
+
+    default:
+    case 1: {
+        /* This one creates separate closed subpaths that correspond to the faces of the extruded shape.
+         * When the LPE is complete, one can convert the shape to a normal path, then break subpaths apart and start coloring them.
+         */
+
+        Piecewise<D2<SBasis> > pwd2_out;
+        // split input path in pieces between points where deriv == vector
+        Piecewise<D2<SBasis> > deriv = derivative(pwd2_in);
+        std::vector<double> rts = roots(dot(deriv, rot90(extrude_vector.getVector())));
+
+        std::vector<double> cusps = find_cusps(pwd2_in);
+
+        // see if we should treat the path as being closed.
+        bool closed_path = false;
+        if ( are_near(pwd2_in.firstValue(), pwd2_in.lastValue()) ) {
+            // the path is closed, however if there is a cusp at the closing point, we should treat it as being an open path.
+            if ( are_colinear(deriv.firstValue(), deriv.lastValue()) ) {
+                // there is no jump in the derivative, so treat path as being closed
+                closed_path = true;
+            }
+        }
+
+        std::vector<double> connector_pts;
+        if (rts.empty()) {
+            connector_pts = cusps;
+        } else if (cusps.empty()) {
+            connector_pts = rts;
+        } else {
+            connector_pts = rts;
+            connector_pts.insert(connector_pts.begin(), cusps.begin(), cusps.end());
+            sort(connector_pts.begin(), connector_pts.end());
+        }
+
+        double portion_t = 0.;
+        for (unsigned i = 0; i < connector_pts.size() ; ++i) {
+            Piecewise<D2<SBasis> > cut = portion(pwd2_in, portion_t, connector_pts[i] );
+            portion_t = connector_pts[i];
+            if (closed_path && i == 0) {
+                // if the path is closed, skip the first cut and add it to the last cut later
+                continue;
+            }
+            Piecewise<D2<SBasis> > part = cut;
+            part.continuousConcat(connector + cut.lastValue());
+            part.continuousConcat(reverse(cut) + extrude_vector.getVector());
+            part.continuousConcat(reverse(connector) + cut.firstValue());
+            pwd2_out.concat( part );
+        }
+        if (closed_path) {
+            Piecewise<D2<SBasis> > cut = portion(pwd2_in, portion_t, pwd2_in.domain().max() );
+            cut.continuousConcat(portion(pwd2_in, pwd2_in.domain().min(), connector_pts[0] ));
+            Piecewise<D2<SBasis> > part = cut;
+            part.continuousConcat(connector + cut.lastValue());
+            part.continuousConcat(reverse(cut) + extrude_vector.getVector());
+            part.continuousConcat(reverse(connector) + cut.firstValue());
+            pwd2_out.concat( part );
+        } else if (!are_near(portion_t, pwd2_in.domain().max())) {
+            Piecewise<D2<SBasis> > cut = portion(pwd2_in, portion_t, pwd2_in.domain().max() );
+            Piecewise<D2<SBasis> > part = cut;
+            part.continuousConcat(connector + cut.lastValue());
+            part.continuousConcat(reverse(cut) + extrude_vector.getVector());
+            part.continuousConcat(reverse(connector) + cut.firstValue());
+            pwd2_out.concat( part );
+        }
+        return pwd2_out;
+    }
+    }
+}
+
+void
+LPEExtrude::resetDefaults(SPItem const* item)
+{
+    Effect::resetDefaults(item);
+
+    using namespace Geom;
+
+    Geom::OptRect bbox = item->geometricBounds();
+    if (bbox) {
+        Interval const &boundingbox_X = (*bbox)[Geom::X];
+        Interval const &boundingbox_Y = (*bbox)[Geom::Y];
+        extrude_vector.set_and_write_new_values( Geom::Point(boundingbox_X.middle(), boundingbox_Y.middle()), 
+                                                 (boundingbox_X.extent() + boundingbox_Y.extent())*Geom::Point(-0.05,0.2) );
+    }
+}
+
+} //namespace LivePathEffect
+} /* namespace Inkscape */
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :