Re: Tumble Tool

Esben,

Please read my reply below.

>> You can also precisely position the camera to rotate an object by:
>> 1) Selecting an object (right mouse button)
>> 2) position the 3D cursor at the center of the object with Shift+S
>>> "Cursor -> Selection"
>> 3) Press the C key to again center the camera where the 3D cursor is.
>
> This is indeed what I want to do, but to move the 3d cursor to the
> center mass of an object, I have to first go into edit mode and then
> select all vertices and then Cursor->Selection.

You have fallen into a well-known Blender user trap of thinking that an
object's center is the same as the center mass of the associated mesh. 
The center of the object and the center of the mass of the mesh are two
different things.

In object mode, select a mesh object and move it around (GKEY, drag
mouse).  Do you see a little (probably pink) dot moving around with the
mesh as you drag it around the screen?  That is the object's center.  The
dot may or may not coincide with the mesh's approximate mass center.  When
you select an object in object mode and snap the cursor to the selection
with the Shift+S menu, the cursor snaps to the object center, regardless
of whether or not the mesh data is anywhere near it.

It will probably help you to think of objects as being separate from
meshes.  An object is a separate entity and it can contain a mesh, an
empty, a lamp, a curve, and more.  If you open up the Outliner window with
a Blender file and start browsing around in there, the relationships
should become a little more clear.

The solution in your case is to move the object center so that it
coincides with your perceived center of the mesh.  The way to do that is
to:

1) in object mode, select the object
2) in the buttons window, switch to the Edit Buttons
3) find the "Center" and "Center New" buttons.  click either of those and
the mesh's calculated center will correspond to the object center.

There's an important difference between the "Center" and the "Center New"
buttons.  The "Center" button will move the mesh data so that it's center
corresponds with the object center.  The "Center New" button is probably
more useful, which does not move the mesh data but instead repositions the
object center to correspond with the mesh data center.  Try moving the
mesh data away from the object center and then pressing a button to see
what it does.

Also of interest is the "Center Cursor" button, which does not move the
mesh data, moving only the object center to be wherever the 3D cursor
happens to be.  As you become more proficient in Blender, this function
will become more useful to you.

Once you have your object center in the middle of the mesh data, you
should then be able to follow the previous instructions to position the
cursor at the object center, and then center the viewport around the
cursor.

David