Definition
Illumination in Patchwork 3D is provided by light sources. These light sources can be any of various types: sky, spot, omni, sun or area. Light sources of all types are grouped into lighting layers, which can be combined to create complex illumination set-ups. The set of visible layers and their coverage provides a total illumination set-up which is used to calculate lightmaps.
Lighting is managed in the 
Lighting tab of the Shaper sidebar. At each level — light sources, lighting layers, and full illumination set-up — settings are available to adjust the lighting properties.