Mostly revert ef01f37

That commit message was a lie, it did not improve performance but actually reduce it significantly...

I had accidentally added a lot of complexity due to the std::list data structure. this approach might seem more redundant, but it's much faster with rectangles (like 100x faster) and doesn't seem to make a difference in the other cases.

Quickhull.h

@@ -149,38 +149,38 @@ private:
         // If the input vector is empty, we're done
         if (input.empty()) return;
 
-        // Find the points which are furthest away from the line
+        // Find the point which is furthest away from the line, add it to the output
+        Point furthest_point;
         float furthest_distance = -1.0;
 
-        std::list<Point> furthest_points;
-
         for (const Point &point : input)
         {
             float this_distance = line.distance_squared_to(point);
-            // It's possible for there to be multiple closests points (e.g. in the case)
-            //  of a rectangle). We need to handle all these properly, so we make a list
-            //  of all points at the furthest distance.
             if (this_distance > furthest_distance)
             {
                 furthest_distance = this_distance;
-                furthest_points.clear();
+                furthest_point = point;
-                furthest_points.emplace_back(point);
-            }
-            else if (this_distance == furthest_distance)
-            {
-                furthest_points.emplace_back(point);
             }
         }
 
-        for (const Point &point : furthest_points)
+        // This seems unnecessarily complicated, but it actually yielded the best results,
+        //  especially when the rectangle edge case is taken into account.
+        for (const Point &point : input)
         {
-            // All furthest points we found are part of the hull, so add them to the output
+            float this_distance = line.distance_squared_to(point);
-            //  and remove them from the input.
+            if (this_distance == furthest_distance)
-            output.emplace_back(point);
+            {
-            input.remove(point);
+                output.emplace_back(point);
+            }
         }
+        // Remove the previously checked points from the input -- we can't do that in
+        //  the previous loop because we can't delete from the list we're iterating over
+        input.remove_if([furthest_distance, line](Point point)
+        {
+            return furthest_distance == line.distance_squared_to(point);
+        });
 
-        Point furthest_point = furthest_points.front();
+        output.emplace_back(furthest_point);
 
         // Build a triangle with these 3 points