GGU-3D-TRANSIENT: "Diffuse sources" menu item

Certain elements can be assigned diffuse sources by defining the area required as a polygon using 4 counter-clockwise points. You will then see the following dialog box:

If you activate the "Add to present sources" check box, the value entered will be added to any diffuse sources already present. If negative entries are made the diffuse source is reduced correspondingly. Existing diffuse sources can be deleted by entering a value 0.