[Algorithms] It looks terrible (was: Lightmap Terrain)

[Klaus H. <k_h...@os...>]

Hi all,

Please have a look at the following image (~310 KB):
http://www.thecore.de/TheCore/shadows.jpg

This lightmap looks majorly terrible, and I'm looking for ways to enhance
this. I use the simple dot-product approach, and I have two light source.
One light source (sun) is to the east, and the other ('anti' sun) is to the
west. I use two light sources, because I don't like ambient. I compute the
light for each texel, and then I cast a ray towards the sun (directional
light). If this ray intersect with the surface before it reaches the sun,
then I decrease the texel's intensity by some amount. I don't reflect or
refract rays. I figured, that reflection probably wouldn't make much sense,
because there's only a few cases where the reflected ray would hit the
terrain again (or am I wrong?).

How can I make this look better? For example, is there a way to have real
penumbrae in the shadows. Of course, I could blur the image, but that just
wouldn't be the same.

Any ideas? Honestly... a simple dot-product (without shadows) looks more
than twice as good (I can upload the same scene without shadows, if
requested).
Niki