What option i have to put Shadows in my games

Hi, i have another cuestion...


what option i have to put shadows in my games...
without using external librarys.. (sorry my english)

i need option, becouse the far objetcs not need detail shadow.. but in the near objet, i won to make a nice shadow..

i use a terrain standar.... and is not flat... so the shadow must be adapted to the terrain...

thanks...