BUG with lights in MR animation

[teocomi]

Hello everybody,

i'm getting pretty mad trying to render an animation in 3ds max 2011 + mental ray, since lights in my scene change randomly intensity during the aimation without any reason!!

 

I attach some frames, as you can see in frame 82 and 83 (the wrong ones) there are strange reflections..! It's even more odd that if I change some random settings (render size, geometry, render region size, camera position) it may render correctly that frame and not others ..

 

Render setting are pretty default ones, lights are photometric, and yes I tried to create new ones..

 

frame 81

frame 82

frame 83

frame 84

 

I also attach a simpler version of the scene, you can see the bug happening in frame 102 and not in 101 for instance...

 

sfaso_luce.max

 

Please HELP me!! Many thaks!!