Why does the Remesh Modifier change object outer dimensions? I am trying to use the Remesh Modifier to reduce the number of polygons in a hemisphere shape (and simultaneously convert the tris to quads), as shown in the Blender page on the topic here. Note how the outer dimensions of the cone stay roughly constant as the Octree Depth increases (Original on left, then increasing Octree Depth from left to right).



However, when I try to use it, it drastically changes the outer dimensions of the hemisphere, such that it only keeps the top section of the hemisphere, as shown in the series of images below. Note how the hemisphere height decreases as the Octree Depth decreases.



Why is this? 
Note: I am using Blender v2.66 (released 2013), which may be the cause.
The problem is resolved by using a closed hemisphere mesh (below left), rather than an open hemisphere mesh (below right).



Using a fully enclosed mesh, the remesh tool retains the outer dimensions of the geometry (without shrinking the input shape) as the Octree Depth is decreased.



Perhaps in future I will close the geometry, apply the Remesh Modifier, and then remove the plane that closes the geometry after the modifier is applied.