Thanks for your response and screen shots MikeJ, but yes it is a definite bug. I tried your same settings and got a very dark gray sky with no sun visible at all. In Vue4 the fog especially is needed for volumetrics because it is this simulation of moisture in the air that allows the light beams and glow to be seen. With a volumetric sky you don't even need lens flares because the sun glows behind all that 'moisture.' Before the update I could render volumetric skies and suns with absolutely no lens flare, just like the image you posted. The glow setting in volumetrics is what really makes the sun sing. The atmosphere controls make sense to me and I had a nicely tweaked sky before things went wonky. I am waiting to see if Steve can re-create the bug, but until then I will re-install from the CD. It may be a Mac only bug. The volumetrics are what made me want Vue in the first place - Bryce cannot do volumetric skies - only materials. You're welcome, I'm glad you're getting to explore what is under the hood - Vue4 is truly a very deep program - and I beta tested Bryce for many years , I should know ; ) I was right in the middle of trying to get sunbeams to come out of the sun (without having to fake it) when I lost everything. I'll save a backup of all my custom presets and re-install I guess. I'll post one of those test images too, if I can re-render them when I go back to the previous version. thanks for answering so quickly : )