GGU-2D-SSFLOW: "Diffuse sources" menu item

Certain elements can be assigned diffuse sourcesby 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 diffuse source" 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. If you click the "Delete all" button, all existing diffuse sources are deleted and you can define a new diffuse source after specifying a new polygon.