I must illuminate completely a series of architectural models in real time .
I tryed to use directional lights , but all the model appear flat without gradient typical of the real illumination.
What kind of lighting you advice me?
Cast shadows and ambient occlusion are often very important for any kind of realistic lighting.
Can you post screenshots, both with full faces, and a wireframe ?
I think, then he will post screenshots, we’ll find out question was much simplier.
But anyway, i agree with ZBuffer that shadows are good way to add depth and realism to scene, also normal mapping and some reflections will do. But i highly doubt that Ambient Occlusion is a good thing to do, the only acceptable case i’ve seen in real time is nvidia AO that you can enable through drivers in HL2. But in real life AO is just a little part of global illumination and it’s barely noticable, so avoid implementations like in typical multiplatform shooters(e.g. Brink), there AO is overused and mostly, a very cheap hack that makes everything look flat.
For all these techniques in OpenGL there are plenty of tutorials in Google.
Unles your are talking about gothic cathedrals with fine details, or wall with apparent stones, modern architecture models gets nothing from normal maps. AO on the contrary is an important part of outdoor lighting for anything not set in space (ie. with either a blue or grey sky).
If using AO, it shouldn’t be too noticable, and a bit of noise on light surfaces looks good with AO.
Why did you use directional lights? That’s the worst choice you could have made. It’s the simplest of the lighting models and should give exactly what you got. You will get no variation in lighting over a flat surface with directional lighting. Try spotlights or local lights, and read about attenuation here: http://glprogramming.com/red/chapter05.html