1 files changed, 158 insertions, 0 deletions
diff --git a/src/toys/ellipse-intersect-toy.cpp b/src/toys/ellipse-intersect-toy.cpp
new file mode 100644
index 0000000..3d65baa
--- /dev/null
+++ b/src/toys/ellipse-intersect-toy.cpp
@@ -0,0 +1,158 @@
+#include <2geom/cairo-path-sink.h>
+#include <2geom/ellipse.h>
+#include <2geom/line.h>
+#include <2geom/polynomial.h>
+#include <toys/toy-framework-2.h>
+
+using namespace Geom;
+
+class CircleIntersect : public Toy {
+    PointSetHandle psh[2];
+    Ellipse ea, eb;
+    Line l[6];
+
+    void intersect() {
+        // This is code is almost the same as in ellipse.cpp.
+        // We use it here to get the lines.
+        double A, B, C, D, E, F;
+        double a, b, c, d, e, f;
+
+        ea.coefficients(A, E, B, C, D, F);
+        eb.coefficients(a, e, b, c, d, f);
+
+        double I, J, K, L;
+        I = (-E*E*F + 4*A*B*F + C*D*E - A*D*D - B*C*C) / 4;
+        J = -((E*E - 4*A*B) * f + (2*E*F - C*D) * e + (2*A*D - C*E) * d +
+              (2*B*C - D*E) * c + (C*C - 4*A*F) * b + (D*D - 4*B*F) * a) / 4;
+        K = -((e*e - 4*a*b) * F + (2*e*f - c*d) * E + (2*a*d - c*e) * D +
+              (2*b*c - d*e) * C + (c*c - 4*a*f) * B + (d*d - 4*b*f) * A) / 4;
+        L = (-e*e*f + 4*a*b*f + c*d*e - a*d*d - b*c*c) / 4;
+
+        std::vector<double> mu = solve_cubic(I, J, K, L);
+
+        for (unsigned i = 0; i < mu.size(); ++i) {
+            double aa = mu[i] * A + a;
+            double bb = mu[i] * B + b;
+            double cc = mu[i] * C + c;
+            double dd = mu[i] * D + d;
+            double ee = mu[i] * E + e;
+            double ff = mu[i] * F + f;
+            double delta = ee*ee - 4*aa*bb;
+            if (delta < 0) {
+                continue;
+            }
+
+            if (aa != 0) {
+                bb /= aa; cc /= aa; dd /= aa; ee /= aa; ff /= aa;
+                double s = (ee + std::sqrt(ee*ee - 4*bb)) / 2;
+                double q = ee - s;
+                double alpha = (dd - cc*q) / (s - q);
+                double beta = cc - alpha;
+
+                l[i*2]   = Line(1, q, alpha);
+                l[i*2+1] = Line(1, s, beta);
+            } else if (bb != 0) {
+                cc /= bb; dd /= bb; ee /= bb; ff /= bb;
+                double s = ee;
+                double q = 0;
+                double alpha = cc / ee;
+                double beta = ff * ee / cc;
+
+                l[i*2]   = Line(q, 1, alpha);
+                l[i*2+1] = Line(s, 1, beta);
+            } else {
+                // both aa and bb are zero
+                l[i*2]   = Line(ee, 1, dd);
+                l[i*2+1] = Line(0, 1, cc/ee);
+            }
+        }
+    }
+
+    void draw(cairo_t *cr, std::ostringstream *notify, int width, int height, bool save, std::ostringstream *timer_stream) override {
+
+        Rect all(Point(0,0), Point(width, height));
+
+        double r1x = Geom::distance(psh[0].pts[0], psh[0].pts[1]);
+        double r1y = Geom::distance(psh[0].pts[0], psh[0].pts[2]);
+        double rot1 = Geom::atan2(psh[0].pts[1] - psh[0].pts[0]);
+
+        double r2x = Geom::distance(psh[1].pts[0], psh[1].pts[1]);
+        double r2y = Geom::distance(psh[1].pts[0], psh[1].pts[2]);
+        double rot2 = Geom::atan2(psh[1].pts[1] - psh[1].pts[0]);
+
+        ea = Ellipse(psh[0].pts[0], Point(r1x, r1y), rot1);
+        eb = Ellipse(psh[1].pts[0], Point(r2x, r2y), rot2);
+
+        for (auto & i : l) {
+            i = Line(0, 0, 0);
+        }
+
+        cairo_set_line_width(cr, 1.0);
+
+        cairo_set_source_rgb(cr, 0, 0, 0);
+        Geom::CairoPathSink cps(cr);
+        cps.feed(ea);
+        cps.feed(eb);
+        cairo_stroke(cr);
+
+        try {
+            intersect();
+            std::vector<ShapeIntersection> result = ea.intersect(eb);
+
+            if (!l[0].isDegenerate() && !l[1].isDegenerate()) {
+                cairo_set_source_rgba(cr, 1, 0, 0, 0.2);
+                draw_line(cr, l[0], all);
+                draw_line(cr, l[1], all);
+                cairo_stroke(cr);
+            }
+            if (!l[2].isDegenerate() && !l[3].isDegenerate()) {
+                cairo_set_source_rgba(cr, 0, 1, 0, 0.2);
+                draw_line(cr, l[2], all);
+                draw_line(cr, l[3], all);
+                cairo_stroke(cr);
+            }
+            if (!l[4].isDegenerate() && !l[5].isDegenerate()) {
+                cairo_set_source_rgba(cr, 0, 0, 1, 0.2);
+                draw_line(cr, l[4], all);
+                draw_line(cr, l[5], all);
+                cairo_stroke(cr);
+            }
+
+            cairo_set_source_rgb(cr, 1, 0, 0);
+            for (auto & i : result) {
+                draw_handle(cr, i.point());
+            }
+            cairo_stroke(cr);
+        } catch(...) {
+            *notify << "Exception";
+        }
+
+        // TODO: draw_handle at intersections
+
+        Toy::draw(cr, notify, width, height, save,timer_stream);
+    }
+
+    public:
+    CircleIntersect(){
+        psh[0].push_back(300,300); psh[0].push_back(450,150); psh[0].push_back(250, 250);
+        psh[1].push_back(350,300); psh[1].push_back(500,500); psh[1].push_back(300, 350);
+        handles.push_back(&psh[0]);
+        handles.push_back(&psh[1]);
+    }
+};
+
+int main(int argc, char **argv) {
+    init(argc, argv, new CircleIntersect());
+    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=4:softtabstop=4:fileencoding=utf-8:textwidth=99 :