Ornlu wrote: "(disregarding ta, which really has nothing to do with illumination at all, but with the proximity of ambient surfaces)" Are you speaking from firm knowledge of the operation of True Ambience in the Bryce render engine, or from assumption? How does your description explain my observations in this thread; http://www.renderosity.com/messages.ez?Form.ShowMessage=1445452 Why should "the proximity of ambient surfaces" be affected by objects that have no ambient setting (the transparent and reflective items)? How do such objects bend and bounce "the proximity of ambient surfaces"? I don't show it in those pics, but if the refractive index of the transparent sphere is changed, the shape of the light pool behind it changes too. If I change the transparent colour of the sphere, the colour of the light pool changes too. How does this equate to "the proximity of ambient surfaces"? The proximity of the ambient surfaces in those pics is constant. The supposedly non-existent illumination is altered by the reflective, refractive and transmission properties of non-ambient objects.