[Effect] mode7

Consider my reply before:

You have to factor in the players viewport angle.

Therefore :

mode7 x: Player.X / scrollingfactor + cos(Player.Angle)

mode7 y: Player.Y / scrollingfactor + sin(Player.Angle)

scrollingfactor is related to player viewport height and screen resolution / mode7 object height and has to be tweaked.

Also keep in mind for FPS purposes, the horizon line has to be at Y viewportheight /2.

If you get the scrolling factor right it might look perfect when you walk up to a wall or walk away from one (forward and backward), but then strafing the floor flies by willie nillie. Then you can adjust it further so there's a sweet spot that seems to work for both fb and strafing motion, but then turning the floor angle turns at a different rate than the walls. Then you can adjust the fov to minimize this, once you do the scrollfactor is once again all wrong. After a lot of "tweaking" I got it pretty much under control.