Global Illumination question

I've recently heard that when rendering a scene if you turn on the GI radius it decreases the rendering time of that scene.Did a little test,turned on the GI radius(value 1) and to my suprise it decreased the render time to almost 35% The scene however was unaffected and looked the same as with GI radius OFF.

After that i started to increase the value of the radius and it increased the render time progressively.

Now my question is how do i know what radius value is appropriate for a scene to look good(so the photons are overlaping properly)in order to decrease the render time?

Another question: Will this trick work the same with FG?

Thanks.:wink:

Goodday sir! is GI radius applicable in autocad 2008?

Ya!Surely you can...08 or 09!