Daylight system > Modify panel > Daylight Parameters rollout > Skylight drop-down list > mr Sky > Confirm prompt.
The mr Physical Sky shader is intended primarily for use in the mental ray Sun & Sky combination. This topic mainly provides information on parameters unique to this component. A number of mr Physical Sky parameters are common to all three Sun & Sky components. For some of those parameters, this topic provides a brief explanation plus a link to the main topic with additional details.
Use these settings to adjust the visible appearance of the sun in the sky.
Disk Intensity—The brightness of the sun.
Glow Intensity—The brightness of the glow surrounding the sun.
Use Custom Background Map—When on but no background map is specified, the background of the rendering is transparent black, suitable for external compositing. If you supply a background shader by clicking the button and then specifying a map or shader, the background of the rendering will come from that shader (for example, a texture map that uses a background photograph). In either case the mr Physical Sky will still be visible in reflections and refraction.
To apply a map or shader to this parameter, click the None button.
Note: The background area in the rendered image's alpha channel is always fully transparent, as is the case in general in Autodesk VIZ.
Inherit from mr Sky—Uses the equivalent settings from the mr Sky Parameters rollout for the remaining mr Physical Sky Parameters rollout settings, except for Aerial Perspective. Default=on.
For further information, see Common Parameters
Haze—The amount of particulate matter in the air. Possible values range from 0.0 (a completely clear day) to 15.0 (extremely overcast, or a sandstorm in the Sahara). Default=0.0.
For details, see Haze.
To apply a map or shader to this parameter, click the None button.
Horizon Height—The vertical position of the horizon. Default=0.0.
For details, see Horizon Height.
Blur—The “blurriness” with which the horizon is rendered. Default=0.1.
At 0.0 the horizon is completely sharp. Generally only values lower than 0.5 are useful, but the full range is up to 10.0 for a horizon that consists of blur only, with no actual horizon at all.
Ground Color—The color of the virtual ground plane. Note that this is a diffuse reflectance value (that is, albedo). The ground appears as a Lambertian reflector with this diffuse color, lit by the sun and sky only, and does not receive any shadows.
To apply a map or shader to this parameter, click the None button.
Tip: Some sky models neglect the influence of bounce light from the ground, assuming only the sky is illuminating the scene. To compare the output of mr Sky with, for example, the IES Sky model, one must therefore set Ground Color to black.
Night Color—The minimum color of the sky: The sky will never become darker than this value. It can be useful for adding things like moon, stars, high-altitude cirrus clouds that remain lit long after sunset, etc. As the sun sets and the sky darkens, the contribution from Night Color is unaffected and remains as the base light level.
To apply a map or shader to this parameter, click the None button.
Red/Blue Tint—Provides artistic control over the redness of the sky light. The default value of 0.0 is the physically correct value (calculated for a 6500K whitepoint), but can be changed with this parameter, which ranges from -1.0 (extremely blue) to 1.0 (extremely red).
To apply a map or shader to this parameter, click the None button.
Saturation—Provides artistic control over saturation of the sky light. The default value of 1.0 is the physically calculated saturation level. Possible values range from 0.0 (black and white) to 2.0 (extremely high saturation).
To apply a map or shader to this parameter, click the None button.
Note: This parameter is for advanced users, and functions only when you use mr Physical Sky is used as a lens shader or volume shader. When used as a lens shader, the aerial perspective “mist” applies to primary rays only; it doesn't appear in reflections. When used as a volume shader, it applies to the entire scene and every ray in it, including reflections and refraction.
Visibility Distance—Aerial Perspective is a term used by painters to convey how distant objects are perceived as hazier and tinted towards the blue end of the spectrum. mr Sky emulates this with the Visibilty Distance parameter. When nonzero, it defines the “10% distance”, that is, the distance at which approximately 10% of haze is visible at a Haze level of 0.0.