Mist

Perhaps Mist's most interesting application is on containers; applying Mist as a volume shader of a transparent object gives the object a murky interior, without adversely effecting rendering times.

Parameters

Overall

Transparency controls the fog's maximum transparency. The fog will never become more opaque than this value. Low values give a more opaque fog, higher values give a more transparent fog.

Affect Alpha controls whether or not Mist applies itself to the alpha channel. With Affect Alpha turned off, Mist will not alter the alpha-channel value.

Color

The artist has two ways of setting the fog's color. With Use Solid Color the artist chooses one Solid Color that is applied in all directions, while Use Map and Bitmap changes the color depending on viewing direction, much like a reflection map, useful in situations such as a sunset, where the fog color is different when looking toward or away from the sun.

Layering

To get the appearance of fog laying on a surface, Layering changes the fog's thickness as a function of height. Base Plane Normal and Base Plane Distance control the layer's vertical direction and position from the world center. Transition Height controls how tall the transitional layer is, and thus how abruptly the fog varies from opaque to transparent.

Falloff

The Falloff settings control the rate at which the fog becomes opaque over distance.

Linear Falloff activates linear decay. At the Linear Start distance the fog is transparent, and the Linear End distance the fog is opaque. Distances between interpolate linearly.

Realistic Falloff uses an exponential function, similar to a true natural fog. Where the Linear falloff has an abrupt end (as an object passes through the End distance, it almost seems to spring into view) the Realistic falloff is more gradual. With Realistic, the artist has no direct control over starting and ending distances, only the fog's overall thickness, controlled with Density.

Custom Falloff allows the artist to specify exactly what he wants as the falloff curve. At the Custom Start distance the fog is transparent, and at the Custom End distance the fog is opaque. At the Custom Middle distance the fog is exactly halfway between transparent and opaque. Distances between are interpolated on a spline curve. (See the discussion on Custom Curves.)

NOTE: If banding occurs when using Mist, simply turn on "Dithering" in the Render dialogue box to correct it.