Preetham-Wilkie environment¶
Description¶
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.
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¶
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>