A question about obj and object data orientation

After reading a few post and some tutorials, it seems to me the a mesh object is (indicatied by the violet ball in the 3D view) and the actual Mesh object data(indicated but the black lines and smaller violet balls in the edit mode and violet lines in the object mode) can have different orientations.

I have learned that they can have different locations in the 3d view and that you use the center,center new and center cursor buttons to change that location.

But if i thougt that they both had the same orientation that was only changed when you rotated the wireframe mesh object. If it is true that then can have different orientation how do you show the axis and their orientation of the object( the purple ball)?? I know you can use draw axis to show the oreintation of the puple mesh.

are you asking if the object center can have its own location/rotation, different from the mesh?

[the answer is no]

when you rotate the mesh in edit mode, you are rotating the object’s data. blender doesn’t remember how the object is oriented in edit mode. This can make it so for example if you rotate a several times cube in edit mode [from different points of view], there is nothing you can do to rotate it back completely.

also, you can apply the rotation/scaling of a mesh [which will reset the mesh’s axes to be like the global ones] with control+a out of edit mode.

z3ro d. So if I understand you correctly the object( the violet ball) and the object data( the wireframe mesh lines) always have th same orientation when you rotate the mesh.?? Is that correct.

I was particularly thinking about the edit mode. I seem to remember some tutorial where the author wanted you to enter the edit mode and leave the object and one orientation and then rotate the mesh into another for some reason. That tutorial is what got me thinking. The way he put it seemed that the object and the mesh could have different orientations but when I turn on draw axis I only see one set of axes arrows.

well, the object can have only one orientation, but it is relative to the the parent’s orientation [or the world if no parent]

and, the mesh and the dot are pretty much one and the same, the dot is merely an indicator of where the center of the object is [and if it is selected or not]

The tut you mentioned possibly had something to do with duplis. In F7 when you set the Track-Axiis and Up-Axiis the axis it uses is the axis of the Object Center (that violet dot). Yet, if you rotate the dupliverted mesh in edit mode then the local axis of the mesh will be offset from the Global axis of the mesh and the allignment wouldn’t be the same as if you had rotated it in Object Mode.


Maybe the distinction between an object and object data will become a little more clear when you consider what ‘Alt+D’ (Duplicate Linked) does vs. ‘Shift+D’ (Duplicate).

‘Alt+D’ creates a new ObjData structure which is linked to the same Object. It creates a new visual “thing on the screen,” but the only thing that’s really distinct between these two “things” is the rotation, size and position of each. All that’s in the ObjData. If you change the materials and certain other characteristics of one (anything that’s in the parent Object structure), the change will simultaneously affect both “things on the screen.”

‘Shift+D’ replicates both Object and ObjData, creating a wholly new instance of each. “Things on the screen” created in this way are entirely distinct.

Erm, it’s Shift D, not Ctrl :slight_smile: