Mask Modes

The masking mode refers to the manner in which masks are combined during expression evaluation. The mode may be either and or.

If the masking mode is and, then masks are combined by finding their intersection (Diagram 1). If the mode is or, then masks are combined by finding their union (Diagram 2). The masking mode may be changed using the Project Defaults option (under the Grid Calc > Edit Modelling Defaults submenu), or by using the set command.

Diagram 1 - AND masking mode

Diagram 2 - OR masking mode

By default, the grid mask for a given grid location is determined by the intersection (that is, logical AND) of all mask flags for all grids referenced in the expression for that point.

If a point falls outside any of the grid areas referenced, then the mask for that point for such a grid is taken to be zero (off).