I’m doing realistic 3d city scene and the questions are:
1.How to get a realistic light (sun light)effects,that will look impressive.I read NEHE tutorial and also the red book ,but I don’t know
witch lights I should combine together to get a nice look.I tried a diffuse light(as sun light )but it looks a little boring. I tried also other combinations and meantime I didnt get a good look.
2.What is the recomended diffuse light position (I’m working with depth about 500 and height about 300)?
As you’ve already surmised, a single directional diffuse light, by itself, isn’t the most realistic solution. Ambient occlusion maps can help, if setup properly. These contain an ambient occlusion term that can be modulated with diffuse lighting to break up the ambient flatness.
Lightmaps can be used to store a static diffuse lighting solution. You can get pretty fancy with these: you could have a nice radiosity solution baked right in, with soft shadows to boot. Of course, these are for static lights, so no moving sun here. But they make for very nice, ultra fast lighting in realtime.
This is a very tough question. The global illumination problem is a big one, and there’s a lot of research going on in this area. I would start with a google for “global illumination”. There’s a ton of info out there in this area. The trick is to creatively bring current hardware to bear on the theory, which can be very tricky indeed.