JavaScriptCollection
diff --git a/‎d3.geo.js‎
Lines changed: 31 additions & 29 deletions b/‎d3.geo.js‎
Lines changed: 31 additions & 29 deletions
@@ -738,37 +738,32 @@ d3.geo.clip = function() {
         o = {source: origin, target: null},
         n = d.length,
         i = -1,
-        j,
         path,
         clipped = [],
         p = null,
-        q = null;
+        q = null,
+        distance,
+        oldDistance;
     while (++i < n) {
       o.target = d[i];
       distance = d3_geo_clipGreatCircle.distance(o);
       if (distance < r) {
-        if (q) {
-          path = d3_geo_clipGreatCircle({source: q, target: o.target});
-          j = d3_geo_clipClosest(path, o, r);
-          if (path.length) clipped.push(path[j]);
-        }
+        if (q) clipped.push(d3_geo_clipIntersect(q, o.target, (oldDistance - r) / (oldDistance - distance)));
         clipped.push(d[i]);
         p = q = null;
       } else {
         q = o.target;
         if (!p && clipped.length) {
-          path = d3_geo_clipGreatCircle({source: clipped[clipped.length - 1], target: o.target});
-          j = d3_geo_clipClosest(path, o, r);
-          if (path.length) clipped.push(path[j]);
-          p = o.target;
+          clipped.push(d3_geo_clipIntersect(clipped[clipped.length - 1], q, (r - oldDistance) / (distance - oldDistance)));
+          p = q;
         }
       }
+      oldDistance = distance;
     }
     if (q && clipped.length) {
       o.target = clipped[0];
-      path = d3_geo_clipGreatCircle({source: q, target: o.target});
-      j = d3_geo_clipClosest(path, o, r);
-      if (path.length) clipped.push(path[j]);
+      distance = d3_geo_clipGreatCircle.distance(o);
+      clipped.push(d3_geo_clipIntersect(q, o.target, (oldDistance - r) / (oldDistance - distance)));
     }
     return clipped;
   }
@@ -799,20 +794,27 @@ var d3_geo_clipGreatCircle = d3.geo.greatCircle().coordinates(function(d) {
   return [d.source, d.target];
 });
 
-function d3_geo_clipClosest(path, o, r) {
-  var i = -1,
-      n = path.length,
-      index = 0,
-      best = Infinity;
-  while (++i < n) {
-    o.target = path[i];
-    var d = Math.abs(d3_geo_clipGreatCircle.distance(o) - r);
-    if (d < best) {
-      best = d;
-      index = i;
-    }
-  }
-  o.target = path[index];
-  return index;
+function d3_geo_clipIntersect(from, to, f) {
+  var x0 = from[0] * d3_radians,
+      y0 = from[1] * d3_radians,
+      x1 = to[0] * d3_radians,
+      y1 = to[1] * d3_radians,
+      cx0 = Math.cos(x0), sx0 = Math.sin(x0),
+      cy0 = Math.cos(y0), sy0 = Math.sin(y0),
+      cx1 = Math.cos(x1), sx1 = Math.sin(x1),
+      cy1 = Math.cos(y1), sy1 = Math.sin(y1),
+      d = Math.acos(Math.max(-1, Math.min(1, sy0 * sy1 + cy0 * cy1 * Math.cos(x1 - x0)))),
+      e = f * d,
+      sd = Math.sin(d),
+      A = Math.sin(d - e) / sd,
+      B = Math.sin(e) / sd,
+      x = A * cy0 * cx0 + B * cy1 * cx1,
+      y = A * cy0 * sx0 + B * cy1 * sx1,
+      z = A * sy0       + B * sy1;
+
+  return [
+    Math.atan2(y, x) / d3_radians,
+    Math.atan2(z, Math.sqrt(x * x + y * y)) / d3_radians
+  ];
 }
 })();