Anyone created a good random terrain generator?

I want to create random worlds during runtime for 3d terrains. I want them to be realistic and varied and smooth enough to move around. Has anyone managed this and willing to give out the code (or some tips)?

Try this one...worked nicely for me.

http://www.robot-frog.com/3d/hills/

That is an awesome tutorial mearrin69... I have been looking for alternatives to Perlin Noise for generating ladscapes for a while now.

Another method to look at is:
http://www.gamedev.net/reference/programming/features/fluidterrain/
It uses fluid simulation to generate a terrain. Looks similiar to Perlin Noise though.

Not that Perlin Noise is bad, it is just that everything seems to use it nowadays... sometimes you want a bit of a different look to things!

There is a perlin noise terrain generator in the code archives that I wrote.

wow. that hill tut mearrin69 linked to is nice. obvious, but nice. You could create tiny map files with this simply by storing hill size and positioning. If I was doing an in-depth game, I'd also include object/enemy positions, and more modifiers, like one to flatten an area for a building.