I recently created some landscape code and added some diffuse lighting to the scene, however, to my disappointment, there are no shadows. I looked around the web for hours looking for ways to get shadows in OpenGL, however they all seemed terribly complicated; and very unique to their own demo programs.
Are there any simple ways to make shadows?
No. Rasterization is very bad at this (even recent AAA games have noticeable shadow artefacts), but everybody lives with it.
Solutions include (approx. from easiest/poorest to best/hardest) :
So the usual trick is to mix beautiful-but-static-only approaches with dynamic-but-not-that-good approaches. For instance, see my tutorials on lightmapping and shadowmapping.