After having s3d installed, you can write your own s3d programs (yeah, that is what this guide is about ;)
#include <s3d.h>should be enough to access the 3d functions. If you want to use keyboard interaction, do
#include <s3d_keysym.h>for the keycode table. Now you can compile your program with
bash$ gcc program.c -ls3d -o program That wasn't that hard, wasn't it?