I modified a copy of "knights on wheels" code so that it loads a terrain and tiles it around the center tile. When the code starts, the car is on the center tile and if I drive the car to the next tile, the car falls off the tile. How can I fix the problem?

physX_open();
level_loadendless("ground.hmp");
terrain_tile(level_ent);
ent_createlayer("skycube+6.dds",SKY|CUBE|SHOW, 0);
pXent_settype(level_ent,PH_STATIC,PH_POLY|PH_MODIFIED);

PhysX seems to have some problems with terrains and scaling... all terrains that are scaled fail for PhysX for me...

You can not really drive a car to the next tile because there is no next tile. The endless level effect works with rendering imaginary images of the same level.

For endless terrain illusion, you must put back the car when it reaches a level border, in just the same way as the endless terrain script does it with the camera. The car is a physics object, so you must disable it before you can put it on a different position.

I havent tried it myself but this is the way it should normally work. Maybe you must overlap the tiles a little, otherwise the car could already fall over the border when its front wheels are outside the level border.