commit 1a90b98832b7b3cc9ab6ec04e320dbf64744e9e3
Author: Mitchell Richters <mjr4077au@gmail.com>
Date:   Fri Oct 7 19:50:50 2022 +1100

    - Duke3D: Ensure player maintains velocity when going through a portal.
    
    * The current setup that's been long-standing has the player come to a complete stand-still for one tic while transiting through a portal.
    * By saving off the velocity difference between the player's pos/opos, we can re-apply that to opos to make the portal transition truly seamless.

See https://voidpoint.io/terminx/eduke32 for more details.