Example #1: a first person character controller mover that does it:
In the gist linked in the above post, look at line 295 for the assembly of the right/forward components of the motion. The line presently reads as:
move = ( playerTx.right * inputMoveX ) + ( playerTx.forward * inputMoveY );
Example #2: a third-person isometric controller that does it:
The relevant work is lines 124 to line 130 in the above file.
Example 2 is part of my proximity buttons full project and the above is a link to one file in the repository.
proximity_buttons is presently hosted at these locations:
https://bitbucket.org/kurtdekker/proximity_buttons
https://github.com/kurtdekker/proximity_buttons