Align an object to a specific face

Question

I usually face this problem when I cut objects to make them printable in my 3D printer. As you may know, you need your object to have a nice base to be printed.

So I usually use bisect to cut an object to different pieces. As in this example:

and I need to rotate the top part to have a face as bottom:

I'll share my workflow in an answer, but I'm asking for a simpler solution, if there were any.

Answer 1

So this is my workflow:

First select the face you want to be the ground of the object, and create a custom Transform Orientation from the N panel:

Then select the new orientation and place 3D Cursor at the face center with ShiftS, Cursor to Selected. You could also move object center to the same place with ShiftCtrlAltC>Object to 3D Cursor.

Now add an emtpy and align it to my custom orientation.

Now parent the object to the empty (CtrlP), clear the empty rotation (AltR), and clear the object's parent keeping transformation (AltP>...).

Finally rotate the piece 180º, and you have the face as the ground.

Answer 2

Try my addon, Mesh Align Plus (we align an object in the example below, but you can also do this to a mesh selection or whole mesh):

Answer 3

You can use vertex snapping to achieve this effect.

Note before we begin: You can activate snapping by holding down Ctrl

1. Enable vertex snapping
   

2. Select all the vertices along the edge of the cut face, then with the pivot point set to anything except active element, press Shift S > Cursor to selected

3. Set the origin of the mesh to the 3D cursor(ShiftCtrlAltC>Origin to 3D cursor) If you don't want to move the origin, set the pivit point to 3D cursor.
4. Add a plane in object mode. we will align the mesh to this plane.
5. Now with the mesh selected, hit R, (lock rotation to the axis of the cut mesh). With snapping turned on, move your cursor over one of the vertices on the plane.

Gif Demo:

Edit: This will work on multiple axis, first perform the snap on the X then the Y. I will note that it is incredibly difficult to get the snapping right. The best technique is to do the rotation in edit mode with snapping set to active.

Answer 4

Although developed in a fork there is a tool that simplifies this requirement.

It works over selected data, in ob and editmode, and developed as a new transform tool. It's not and addon. You must specify 1, 2, or 3 points as origin (using snap tool most times), and then the same number of points as destiny. First point is a translation. With the second point it performs and axis match, and with the 3rd point a plane match (rotating over the axis defined).

The project also allows to move the view during transform, which is also great.

https://vimeo.com/161994522

http://www.mechanicalblender.org/features/match-tool.html

Answer 5

You have an object that is rotated in an strange angle.

• You add a default cube then by use of snapping as in below you drag it to the surface that you want to be un-turned of a strange angle

• As a result the cube will be turned into the same orientation.

• Next you select your object then the cube and press CTRL+J. This join the object, and by doing so your object gets a new origin
  which is rorated as the cube.

• Now you can go to your object and undo any strange rotations by setting the object roations to zero