Lighting, shadows& some other stuff
 

First, hello all ;)
New here...

I'm having a hard time understanding some weird things that happen around maya 4 and mental ray 3.0 (i guess).
Frankly, i don't understand how to make proper shadows and lighting :)

Let's say we have a long tube and a point light inside it. The light should come out only from the opening of the tube, right? wrooong...it acts like the tube doesn't exist.
I thought the lack of shadows must be the reason. I checked raytraced shadows, and it works ok, but the shadows are sharp, not smooth (of course, they are raytraced).
Mray seems to ignore dmap shadows.
Is there a solution to this?

Frankly, i'm quite puzzled about shadows, lighting, final gathering and global illumination...
I understand each concept very clearly taken separately, but i'm lost in digging the interaction between all of them. :banghead:
Any help?