I saw the aum 44. it makes the world "endless" if I want it to, am I right? how is it that if I use different terrains with different "types" one being a huge mounty terrain, one forrest, thats ok for me to make, what I dont understand, is how will these "stitch" together if I create the terrains from different heightmaps, or would I have to make them compatible through med-3dsmax etc?

i think you have to create the complete world as one, and split it.
Now you make a model/terrain of each part. at the end, it will look seamless together.

Hmm, or I can make serveral terrains and stitch them together but not directly, inbetween them, there would be transition terrains slowly changing or rapidly at some spots, this way I think would be easier and more controllable to which region I am supposed to be in.

zone mapping.. urgg i had to so that with space game, gave me headaches..

You can write a script, wich moves the vertecies of the terrain, and smoothes out the edges.
This way you can creates Terrains wich get aligned by code.

what would you suggest for large and many different terrains? performance wise, using code to align them would it cost much performance if I use code to align every terrain?

I'd say that the easiest (and at the same time the fastest) method would be to create a huge heightmap that includes all the terrain pieces, and then split it and create the individual terrains. If you make sure that the bitmap area that is split has the same color (height) on both sides, your terrain pieces will tile seamlessly.

Splitting is the esiest way.

Having some script running over the side vertices of a terrain would work as well, but then you need to have loaded all touching terrains in order to be able to smooth out the vertex positions.

then again, regarding seamless world, should I place my entities and such through lite-c? because it doesnt seem like wed likes too big levels, objects dissapare in the views.

I use ent_create to create the entities at runtime, keeping their offset in relation to their parent terrain / level piece. I use a while(1) loop for that.