Arrow Group Industries LM86 Manual de usuario descargar pdf (Pagina 29)

Maxwell Render 2.5 User Manual

Chapter 7. Setting up environment lighting | 29

• Sun: Switch direct sunlight on/ off.

• Sun Temperature: Temperature of the sun’s spectral radiation. The default value

of 5777ºK is the most common value measured outside the Earth’s atmosphere.

Lowering this value will give the sky and scene illumination a yellow tint, higher

values will give the illumination a blue tint. Although it is possible to change this value

for different looks, it is better to leave it at default and instead change the other

atmosphere parameters for accurate and predictable results.

• Sun Power: A multiplier that controls the amount of light emitted from the sun.

Higher values than the default 1 will make the sun emit more light, lower values will

emit less. A value of 2 means the sun in your scene emits twice as much light as the

Earth’s sun.

• Planet Reectance: Controls the percentage of light reected from the planet

surface back into the atmosphere. Changing this value will brighten/ darken the overall

sky and scene illumination with lower values giving a darker result. Common values

are 26-32 %. This parameter is similar to the common term “Planet Albedo”, which

refers to light reected from the planet surface plus the light reected from cloud

coverage. Albedo is the ratio of light reected by an object to the total amount of light

it receives. The albedo of an object can range from 0 (0% light reected back) to 1

(100% light reected back). The average albedo for the Earth is 0.3, which means on

average the Earth reects 30% of the light it receives back into the atmosphere. The

albedo can vary greatly. Fresh snow has an albedo of about 0.8; forested areas have

an albedo of 0.05-0.10, etc. Regional albedo values can be found online.

F.01 Globe (only available in studio)

Gas Properties:

• Ozone: The amount of ozone gas in the atmosphere. The default value of 0.4

centimeters means that if you gathered all the ozone in a vertical column stretching

through the entire atmosphere, you would get a stack of ozone of 0.4cm high. Raising

this value will result in the sky and scene illumination having a more blue tone,

lowering it will produce a more yellow tone.

• Water: The amount of water vapor in the atmosphere. It is measured in centimeters,

in the same way as ozone. This setting may not have much inuence on the look

of the sky at midday, but will have a clearer effect at sunrise and sunset. In those

situations, raising the water value will make the sky look heavier and less saturated,

with a red/ orange tone at the horizon, while the rest of the sky will turn a darker

blue.

Aerosol Properties: The physical sky model in Maxwell Render adds parameters for

aerosols: small particles found in the atmosphere. Light interacts with these particles as it

travels through the atmosphere. They absorb and scatter light, which has a big impact on

the coloration of the sky and scene illumination. The last four parameters control various

aspects of the aerosols found in the atmosphere.

• Turbidity Coefcient: Denes the concentration and amount of particles in the

atmosphere. A value of 0 creates a perfectly clear sky (in which case the next three

parameters won’t have any effect). 0.01 is a good value for low turbidity, e.g. a sky

with very few aerosols in it so that it will appear almost clear. 0.04 is a good medium

value and 0.1 is a high value. Raising the amount of particles in the atmosphere will

usually result in a darker sky and darker scene illumination, but the effect depends

also on the Scattering Asymmetry parameter (see below). In bright daylight situations

and with a positive Scattering Asymmetry, raising the Turbidity Coefcient will at rst

desaturate and brighten the sky. Raising the parameter further will start to darken

the sky. With negative asymmetry, the sky will begin to desaturate and darken. The

following images show this effect:

Raising the Turbidity Coefcient in sunset situations will darken the sky. Remember

that you can also raise the ISO of the camera in these cases, which can reveal an

interesting sky.

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Arrow Group Industries LM86 Manual de usuario Pagina 29

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