Hi all. I'm trying HDRI for the first time. Please, don't consider the s**tty environment, I'm way behind in setting the scene properly. What perplexes (?) me is another thing. This first image is rendered with Premium Settings, True Ambience, 64rpp. Rendertime 4m43sec.

This second image is rendered with normal settings. Rendertime 6 seconds. The settings on the HDRI sphere are the same. 100 diffuse, 100 ambient, both diffusion and ambience driven by the picture in channel A. There's so big a difference? But I don't understand why, having sunlight disabled in both images (both, I repeat, have the same settings), I see perfectly even when I don't use True Ambience. Please forgive me if this is trivial, but... anyone can enligthen ;-) me about this? Thanx in advance, Stefano

Ok, reflective surfaces do not need true ambiance to show up. They work as follows, sort of a reverse reality so bear with me. 64 "visual" rays per every pixel of the image are sent out from a single point located at the camera's location, these rays bounce off reflective objects onto other objects, the final resting place of the ray is then transfered as alpha back onto the original reflective sphere, IE you see a reflection. If you have the ambiance of your HDRI sphere turned on, you will notice that even without any lights the HDRI image will show up. (This is however NOT true if you set the ambiance of the HDRI sphere to 0.) You can get the best ambiance and difusion of the HDRI image by placing the middle Amb and dif marbles under your HDRI texture. That way the white spots will be whiter and the dark spots darker. (also if you greatly increase the resolution of your HDRI image in photoshop, then apply a gaussian blur untill it's no longer pixilated you will get a much better effect. True ambiance comes into play when you are using a non reflective surface. IE if you look in my gallery: These images use 0 direct lighting and non reflective surfaces (on some) yet still are lit in a GI fashion. http://www.renderosity.com/viewed.ez?galleryid=340763&Start=13&Artist=Ornlu&ByArtist=Yes http://www.renderosity.com/viewed.ez?galleryid=340081&Start=13&Artist=Ornlu&ByArtist=Yes http://www.renderosity.com/viewed.ez?galleryid=331596&Start=13&Artist=Ornlu&ByArtist=Yes http://www.renderosity.com/viewed.ez?galleryid=332086&Start=13&Artist=Ornlu&ByArtist=Yes Non reflective surfaces utilize True ambiance by acting like a reflective surface but only using light values from the final destination of the ray. There is also a falloff value in true ambiance as well. IE the closer the objects are to each other, the greater the light transfer between the two. Just like real life. Sometimes you will notice that your renders (with no lights and non reflective surfaces) will come out too dark. In this case take spotlights and shine them up at the bright spots of your HDRI sphere (NOT onto your scene, but up at the sphere) If you want, for a final touch, put a omni light with 1 brightness and no falloff up by one of the light sources on your hdri image, set it to blurry shadows. This is how you achieve the most realistic lighting.