BoxesNode: improve bounding box calculation, mention remaining issue

Nodes/BoxesNode.cc

@@ -98,9 +98,10 @@ void
 BoxesNode::
 boundingBox(Vec3d& _bbMin, Vec3d& _bbMax)
 {
+    // FIXME: this assumes matrices to only consist of vectors up to unit length
     for (const auto &be: elem_) {
-        _bbMax.maximize(be.pos + Vec3d(1.,1.,1.));
-        _bbMin.minimize(be.pos + Vec3d(-1., -1., -1.));
+        _bbMax.maximize(be.pos + Vec3d(scaleFactor_,scaleFactor_,scaleFactor_));
+        _bbMin.minimize(be.pos + Vec3d(-scaleFactor_, -scaleFactor_, -scaleFactor_));
     }
 }