Preetham-Wilkie environment

Description

../../../_images/preetham.jpg

Scene lit by a Preetham-Wilkie environment

Environment The Preetham-Wilkie environment simulates sun and the atmosphere lighting of the earth’s surface. It is based on the work A Practical Analytic Model for Daylight - University of Utah. Sky polarization is modeled according to An Analytical Model for Skylight Polarisation, Wilkie et al.(2004)

The zenith direction (or normal to the horizon plane) may be set to any value in scene coordinates.

../../../_images/preetham2.jpg

Outdoor scene lit by a Preetham-Wilkie environment

The sun position can be adjusted to any direction in the sky. The turbidity parameter controls the amount of scattering due to mist and dust. It can be set to any value between 2 and 6.

Note

Up to Ocean 2015, this environment was named “skylight”. It has been renamed to “Preetham-Wilkie” in Ocean 2016 with the introduction of another skylight model, the Hosek-Wilkie environment

Children Nodes

Spectrum albedo The ground albedo spectrum

Parameters

name type description
sunpos vec3 The sun direction
turbidity real The turbidity, or haziness, of the atmosphere. Must be between 2 and 6
zenith vec3 Zenith direction, allows for instance switching between Z-top and Y-top conventions
atmosphere boolean Disabling this removes the atmosphere, which simulates the sun viewed from space

Ocean XML 4.0 example

<environment type="preetham" name="environment">
   <prm sunpos="-0.4629      -0.8201 0.3365"/>
   <prm turbidity="2"/>
   <prm atmosphere="true"/>
   <prm zenith="0 0 1"/>
   <spectrum type="uniform" name="albedo" value="0.5"/>
</environment>