V-Ray for Rhino Manual - Rum

Adding the V-Ray Sky
Previously we were simply dealing with the only the V-Ray
Sun, but now lets go ahead and add the V-Ray sky. In the
environment rollout of the V-Ray options, click on the "m"
next to GI parameters. You must have Indirect Illumination
enabled to access this, so enable it if you have not already.
Clicking the "m" should bring up the texture editor, and
under Type select Sky. At the top you will notice the option
to select a light source. Click on that button and select the
light that was created via the sunlight command. Now V-
Ray knows where the sun direction is coming from, and this
is an important step for having the Sun and the Sky working
together. Lastly, there is an option next to the button that
says Override Sun's Parameters. This allows separate settings for the Sun and the Sky, but for simplicity
and continuity it is recommended to have this unchecked. Now go ahead and repeat this process for the
background. If we render again we'll notice that our white ground plane has a slightly blue hue to it.
This is due to the influence of the sky on our scene.
Time of Day and the Sun’s appearance
Now that we have added the sun and sky, let’s see how the sun reacts to changing the time of day. In
order to change the position of the sun, select the sun and go to the light properties. At the top of the
window is a button named Modify. Click on the button and it will bring up the Sunlight window and you
can change the position. Now the appearance of the scene has completely changed sole based on the
position of our sun. This allows users the flexibility to worry only about the time of day rather than
adjusting the appearance and intensity of the sun and the background.
Morning Mid-Day Evening
Changing the Sun’s Appearance with Turbidity
Although the time and position of the sun will have the most affect on the appearance of the Sun and Sky,
there are several other controls that will be helpful in adjusting their appearance. Turbidity essentially
changes the amount of dust that is in the air. Values on the lower end or the spectrum will create a very
clear blue sky as you would see in the country side. Having larger values will make the sky slightly
yellow or orangish as you would see in the city. Think of turbidity almost as a control for the haziness of
the sky.
Turbidity= 2, Clear Day Turbidity= 5, Slightly Hazy Turbidity= 8, Very Hazy Day
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