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In fact, a key word in IDL is "diffuse". Poser only deals with diffuse secondary lighting. It does not deal with specular effects, which is shame. Most other apps that do some form of GI do it fully.

i never heard of specular bouncing.

specular is a cheat for reflections. and we can have more bounces for reflection. so if we could use soft reflections we could do specular bouncing

from what  i understand GI and IDL was always only diffuse.