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FlightGear Newsletter August 2015: Difference between revisions
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== Development news == | == Development news == | ||
=== Atmospheric Light Scattering === | |||
==== Irradiance maps ==== | |||
As part of a more detailed interior model effect, the ALS framework now offers the possibility to select irradiance maps for the cabin. What is this, and what is it for? | |||
Most simple rendering schemes make a difference between directional (specular and diffuse) light and non-directional (ambient) light. However, in reality indirect light is not really non-directional. Even if the sun (the main source of directional light) is hidden by an overcast layer, the sky is still brighter than the ground, i.e. upward-facing surfaces will be brighter than downward-facing surfaces. The indirect light has a weak directionality - it is stronger from the zenith than from the ground, but it is never really absent. | |||
Irradiance maps modify the ambient light channel to mimic these effects. ALS has long used an open sky irradiance map for the terrain and the exterior of models, but the interesting thing is that irradiance is different in enclosed spaces. In particular, in a GA aircraft cockpit, the light usually doesn't fall through the ceiling but through the windows, i.e. the irradiance distribution is strongest at the horizon. In contrast, in a fighter cockpit, most of the light comes from directly above. | |||
The most pronounced visual effect of irradiance is that it sculptures the 3d-structure of objects even in the absence of direct light by a gentle shading. Consider the interior of the C-172p rendered without an irradiance map in the absence of direct light underneath full cloud cover (i.e. using omnidirectional ambient light): | |||
[[File:Als-interior-irradiance01.jpg|600px|C-172p cabin interior rendered without irradiance and grain map]] | |||
Thes scene appears largely bland and featureless. Now compare with the second scene rendered with an irradiance map maximizing the horizontal ambient light (where the windows are located) - suddenly gentle shades sculpt the 3-dim structure of the roof: | |||
[[File:Als-interior-irradiance02.jpg|600px|C-172p cabin interior rendered with irradiance and grain map]] | |||
In addition, the effect also allows to specify an internal residual ambient light (e.g. the illumination of the cockpit from lit instruments) - with its own irradiance map, thus the glow of the instruments will produce a soft light coming from the front of the aircraft into the cabin. | |||
Read more on [[ALS technical notes]]. | |||
== In the hangar == | == In the hangar == | ||