Protect against division by zero in QuadTreeBuilder

This could only happen when there's one leaf in the tree, or all the objects
happen to have the same position. Noticed by Csaba Halaz

diff --git a/simgear/scene/util/QuadTreeBuilder.hxx b/simgear/scene/util/QuadTreeBuilder.hxx
index 2c5c4bf558c0599f147cc87571bd24daed809fc5..62734e3b1856e16067f16813023305c80a422bc8 100644 (file)
--- a/simgear/scene/util/QuadTreeBuilder.hxx
+++ b/simgear/scene/util/QuadTreeBuilder.hxx
@@ -80,10 +80,14 @@ public:
     {
         using namespace osg;
         const Vec3 center(_getLocalCoords(obj));
-        int x = (int)(_dimension * (center.x() - _min.x())
+        int x = 0;
+        if (_max.x() != _min.x())
+            x = (int)(_dimension * (center.x() - _min.x())
                       / (_max.x() - _min.x()));
         x = clampTo(x, 0, (_dimension - 1));
-        int y = (int)(_dimension * (center.y() - _min.y())
+        int y = 0;
+        if (_max.y() != _min.y())
+            y = (int)(_dimension * (center.y() - _min.y())
                       / (_max.y() - _min.y()));
         y = clampTo(y, 0, (_dimension -1));
         _addLeafObject(_leaves(y, x), obj);