...
a frame on the bottom of the tree will allow to select the material: Air and expect to be assigned to groups of entities.
In general a recommendable workflow is to create first the groups of entities and to apply in a second step the calculation properties to these groups, but for simple cases it is possible to create automatically the group during a selection, pressing the Select button
- Click Select and select the surface. Press <Esc> when this step is finished, and then press Ok to validate it (the automatic group name could be changed before its validation)
- Choose then Point Weight, and the frame to assign it to points will be showed
- Enter the value 1e3 in the Weight box. Click Select and select the upper corner point. Press <Esc> when this step is finished, and then Ok to accept it.
...