In Carrara 3 manual, it did not give enough information how to use with GI. I thought I should create new thread about GI here. So someone can share tips how to use it. ---------------------------------------------- It seem that everyone have common problem with skylight because both background and atmosphere is light source to GI at the same time. I could not make GI to work with either one background or skylight separately. Atmosphere color is not considered lightsource unless the dirty gas reflect the colors. Sky blue dont make us look like smurfs. Background and atmosphere should be separated to GI with scaler each. I run some scene wizard and tested eovia's precreated GI scenes. I am puzzled that some of their scenes were able to disabled skylight eventhough if I turned it on. I would like to be able to use just the background to give some GI effect to the ground and objects as if it was a sun that give off some colors. Did you have any success on realistic light environment like I described with what Global Illumination should be?

I have recently stopped using sky light rendering, and have resorted to using indirect lighting. Im my gallery,edge of the ocean 2 was set up using the atmosphere setting. I played with the clouds and turned the ground plane a shade of blue. i used one distant light source to white, and i used indirect light, not sky light when rendering. I put 2 cubes and scaled them so that i have a wall behind the camera in my scene so that light will bounce out and light the front of the subject. I hope this helps. regards, E

Very good tips. Thank you for sharing with us.

I've been using a dome over my scenes that glows pretty well with indirect lighting turned on. No lights are used. The Carrara 3 manual states that glowing objects (like street lamps at night) do not light up other objects in a scene. But I think Eovia meant when indirect lighting isn't being used.

What? Smurfs? The observation that sky light was blue was made back in the Rennaisance. It is one of the key facts behind the standard theatrical lighting set-ups, as well as typical painting of highlights and shadows in my business. The blue effect is due to Rayleigh scattering (first described by John Rayleigh in 1870). The shorter wavelengths (of the full spectrum coming from the sun) are absorbed more often by gas molecules of the atmosphere. When they are re-radiated, they are no longer directional but instead are scattered through the thickness of the atmosphere. What remains of the sunlight is thus, also, more yellow than it would be. By the way, you can simulate this effect at home with a glass jar full of water with a little milk in it, a dark room and a strong flashlight. The reasons why we don't look like Smurfs (at least not usually) are two; the main reason is that the effect of this blue sky light is overpowered by the effects of direct sunlight and often washed out by interobject reflectivity of all the other material in the vicinity. If you are standing near a large building it will block all the blue from that side (think of the skylight as being from a dome at infinate distance from the scene), and paint the subject with the whitish light of sunlight off concrete. The other is that our eyes, unlike cameras, are self-correcting. We set our own "white point" constantly. Ever notice how, when you go indoors in the middle of the day all the lights look nasty and yellowed? But then, if you visit the same building in the middle of the night, the lights will look almost white. A last point is that the skylight is not a constant. On an overcast day, much more light is scattered, and shadows become very soft and pale. These are good days for photographs. During sunset and sunrise the scattering becomes more pronounced, with more of the shorter wavelengths removed from the sunlight -- and many of those are "lost" (sent to light areas off on the horizon) before they reach your present viewpoint. Thus, both sun and sky go through orange and reds, and blues are almost completely removed.

I am aware about the true skylight and its chemistry but Carrara is using it incorrectly. Like I stated before that the backdrop and skylight should have scaler separately.

I did a scene just now with no indirect lighting and found that reflective objects act as light sources when placed near glowing objects that won't light anything.

I agree with you there, Waldo. At least the level of general scattering and skylight can be adjusted in reference to each other. I found in experimenting that the skylight effect in Carrara is very sensitive to small changes in hue and value. It is a bit hard to work with, tho, with all the controls interacting the way they do. I'd prefer to see them completely seperated.

echo871 Thanks for the tip about setting up the wall and a reflection. I'll have to try that w/ my next render.

Was discussing this with a friend recently. He points out that photons aren't super-intelligent. If a blue photon hits your eye (aka from the sky), it also hits your skin. That's, in a nutshell, the principle of the HDRI render; what is in the surrounding image is also the available light on the object you are rendering!