1 files changed, 86 insertions, 0 deletions
diff --git a/src/toys/precise-flat.cpp b/src/toys/precise-flat.cpp
new file mode 100644
index 0000000..0113619
--- /dev/null
+++ b/src/toys/precise-flat.cpp
@@ -0,0 +1,86 @@
+/**
+ * efficient and precise flattening of curves.
+ * incomplete rewrite (njh)
+ */
+#include <2geom/d2.h>
+#include <2geom/sbasis.h>
+#include <2geom/bezier-to-sbasis.h>
+
+#include <toys/path-cairo.h>
+#include <toys/toy-framework-2.h>
+
+using std::vector;
+using namespace Geom;
+
+unsigned total_pieces_sub;
+unsigned total_pieces_inc;
+
+class PreciseFlat: public Toy {
+    PointSetHandle hand;
+void draw(cairo_t *cr, std::ostringstream *notify, int width, int height, bool save, std::ostringstream *timer_stream) override {
+    cairo_set_line_width (cr, 0.5);
+    
+    D2<SBasis> B = hand.asBezier();
+    D2<SBasis> dB = derivative(B);
+    D2<SBasis> ddB = derivative(dB);
+    cairo_set_source_rgb(cr, 0,0,0);
+    cairo_d2_sb(cr, B);
+    cairo_stroke(cr);
+    
+    // draw the longest chord that is no worse than tol from the curve.
+    
+    Geom::Point st = unit_vector(dB(0));
+    double s3 = fabs(dot(hand.pts[2] - hand.pts[0], rot90(st)));
+    
+    SBasis inflect = dot(dB, rot90(ddB));
+    std::vector<double> rts = roots(inflect);
+    double f = 3;
+    for(double rt : rts) {
+        draw_handle(cr, B(rt));
+        
+        double tp = rt;
+        Geom::Point st = unit_vector(dB(tp));
+        Geom::Point O = B(tp);
+        double s4 = fabs(dot(hand.pts[3] - O, rot90(st)));
+        double tf = pow(f/s4, 1./3);
+        Geom::Point t1p = B(tp + tf*(1-tp));
+        Geom::Point t1m = B(tp - tf*(1-tp));
+        cairo_move_to(cr, t1m);
+        cairo_line_to(cr, t1p);
+        cairo_stroke(cr);
+        //std::cout << tp << ", " << t1m << ", " << t1p << std::endl;
+    }
+    
+    cairo_move_to(cr, B(0));
+    double t0 = 2*sqrt(f/(3*s3));
+    //std::cout << t0 << std::endl;
+    cairo_line_to(cr, B(t0));
+    cairo_stroke(cr);
+    Toy::draw(cr, notify, width, height, save,timer_stream);
+}
+
+public:
+PreciseFlat () {
+    for(unsigned i = 0; i < 4; i++)
+        hand.pts.emplace_back(uniform()*400, uniform()*400);
+    handles.push_back(&hand);
+}
+
+};
+
+int main(int argc, char **argv) {
+    init(argc, argv, new PreciseFlat());
+
+    return 0;
+}
+
+/*
+  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 :