The image above is a jeep I modeled following this tutorial.
Below to the left, we have the cursor and to the right the 3d manipulator (or selection):
The cursor’s position can be set by left-clicking. Its position determines where a new object will be centered.
The 3d manipulator is set at the object center of mass when it is created. You cannot change its relative position with the object in the object mode. So if you try to move the object away, this manipulator will move together. But when you enter edit mode, the manipulator is different from the object one (you can see the object manipulator in edit mode: it’s the pink dot). Thus, if you move the object in edit mode, the object manipulator won’t move and you change their relative position.
It is possible to set the position of the cursor or the 3d manipulator using the snap menu (Shift+S). Remember that selection = 3d manipulator.
The behaviour of these commands are different for the 3d manipulator in object and edit mode. Let’s consider first the object mode:
- “Selection->Grid” moves the 3d manipulator to the nearest intersection of the grid.
- “Selection->Cursor” sets the 3d manipulator position with the cursor position.
- “Selection->Center” does not apply to object mode (as far as I know)
Let’s now consider the edit mode:
- “Selection->Grid”: the same as in object mode.
- “Selection->Cursor” moves the 3d manipulator and all selected vertices to the position of the cursor.
- “Selection->Center” moves all selected vertices to the position of the 3d manipulator.
And now the cursor commands:
- “Cursor->Selection” sets the cursor position with the 3d manipulator position.
- “Cursor->Grid” moves the cursor to the nearest intersection of the grid.
- “Cursor->Active”: in object mode it places the cursor in the center of the last object selected.
There’s another useful shortcut which places the cursor in the grid origin: Shift+C
