pre pass question

[Sawyer]

I am watching the pre passes and I have noticed this a bit but I wanted to know whats happening. Current image:


I have irr map set to med - it takes 4 prepasses the last one is almost black except for the areas around a light source. I change the set up to LOW and I still have 4 prepasses but numbers 3 & 4 are almost black and render lighting fast. Why is this? I had thought that prepasses were defined by the Irr map.

Thanks

[percydaman]

make sure you dont have materials using interp glossies?

[Sawyer]

Yes I had thought I had none. I was wrong. Thank you Percy for getting me to double check.