1 files changed, 57 insertions, 0 deletions
diff --git a/experimental/Intersection/QuadraticBezierClip.cpp b/experimental/Intersection/QuadraticBezierClip.cpp
new file mode 100644
index 0000000000..1114d74398
--- /dev/null
+++ b/experimental/Intersection/QuadraticBezierClip.cpp
@@ -0,0 +1,57 @@
+#include "CubicIntersection.h"
+#include "LineParameters.h"
+#include <algorithm> // used for std::swap
+
+// return false if unable to clip (e.g., unable to create implicit line)
+// caller should subdivide, or create degenerate if the values are too small
+bool bezier_clip(const Quadratic& q1, const Quadratic& q2, double& minT, double& maxT) {
+    minT = 1;
+    maxT = 0;
+    // determine normalized implicit line equation for pt[0] to pt[3]
+    //   of the form ax + by + c = 0, where a*a + b*b == 1
+    
+    // find the implicit line equation parameters
+    LineParameters endLine;
+    endLine.quadEndPoints(q1);
+    if (!endLine.normalize()) {
+        printf("line cannot be normalized: need more code here\n");
+        return false;
+    }
+
+    double distance = endLine.controlPtDistance(q1);
+    
+    // find fat line
+    double top = 0;
+    double bottom = distance / 2; // http://students.cs.byu.edu/~tom/557/text/cic.pdf (7.6)
+    if (top > bottom) {
+        std::swap(top, bottom);
+    }
+    
+    // compute intersecting candidate distance
+    Quadratic distance2y; // points with X of (0, 1/2, 1)
+    endLine.quadDistanceY(q2, distance2y);
+    
+    int flags = 0;
+    if (approximately_lesser(distance2y[0].y, top)) {
+        flags |= kFindTopMin;
+    } else if (approximately_greater(distance2y[0].y, bottom)) {
+        flags |= kFindBottomMin;
+    } else {
+        minT = 0;
+    }
+
+    if (approximately_lesser(distance2y[2].y, top)) {
+        flags |= kFindTopMax;
+    } else if (approximately_greater(distance2y[2].y, bottom)) {
+        flags |= kFindBottomMax;
+    } else {
+        maxT = 1;
+    }
+    // Find the intersection of distance convex hull and fat line.
+    x_at(distance2y[0], distance2y[1], top, bottom, flags, minT, maxT);
+    x_at(distance2y[1], distance2y[2], top, bottom, flags, minT, maxT);
+    x_at(distance2y[2], distance2y[0], top, bottom, flags, minT, maxT);
+    
+    return minT < maxT; // returns false if distance shows no intersection
+}
+