Simply adding an Environment Map automatically enables a skydome_light with no other input required. The 'skydome_light' and background shader is constructed under the hood, and no extra light creation is required.

 

The lights page has more detail about the controls. The only additional parameters are:

Color

 The skydome_light has a texturable color slot so that you can map a texture to be used for IBL.

 

Intensity

Resolution

The resolution attribute should be used with care. The higher the resolution value, the longer the skydome_light will take to precompute the importance tables for that light. For high-resolution maps, this can be very slow.

Format

Portal Mode

Contribution

Camera

Transmission

Diffuse / Specular / SSS / Volume

AOV Indirect

 

The atmosphere_volume will not work with atmosphere_volume. You must use regular lights that have a precise location and size, and inverse-square decay.