The Environment tab controls the environment which will be used in the exported MXS, and contains all of the parameters necessary to control each Environment Type. There are three main types of environment available; Sky, Image Based, and None. The environment for a scene is set by using the drop-down list contained in the main Environment group.
The sun may be enabled, regardless of the chosen type of environment. It may either use a physical model based on temperature, or a custom one, in which its color is directly specified by RGB value. Its intensity and radius may be modified as well; though this is not necessarily good for achieving realism, it can be useful in some cases where softer sun shadows may be desired, to create dramatic compositions, or in certain circumstances, to speed up rendering (since parallel rays are difficult to resolve).
In this mode, environment lighting comes from a dome of light, with controls provide for defining the colors at the horizon and zenith, as well as the angle for the gradient between them, and the overall intensity of the illumination.
In this mode, a physical model is used to simulate a real world sky.
The Image Based Environment Type allows you to light the scene using HDR (High Dynamic Range, i.e. MXI, EXR, HDR) images. There are four Image Based Channels provided: Background, Illumination, Reflection, and Refraction; each may be disabled, or set to use a specific HDR image, the same settings as the Background Channel, the Active Sky. for more information on how these channels are used, see Image Based Lighting.
Besides these per-channel parameters there are also three other main parameters, which apply to Image Based lighting as a whole:
This option turns on render-time pixel-interpolation for environment HDR images.
Adjusts the overall intensity of all channels.
This determines the type of sky to use, for channels set to use Active Sky.
When using Image Based environment, the sun will only be seen when the Illumination channel is set to use Active Sky.