This would probably be a flagship module, adapted to Foundry v9 to respect the vision rules, would certainly be essential.
Dnd 5e. DMG pg 251 Line of Sight: To precisely determine whether there is line of sight between two spaces, pick a corner of one space and trace an imaginary line from that corner to any part of another space. If at least one such line doesn't pass through or touch an object or effect that blocks vision - such as a stone wall, a thick curtain, or a dense cloud of dog - then there is line of sight.
This would probably be a flagship module, adapted to Foundry v9 to respect the vision rules, would certainly be essential. Dnd 5e. DMG pg 251 Line of Sight: To precisely determine whether there is line of sight between two spaces, pick a corner of one space and trace an imaginary line from that corner to any part of another space. If at least one such line doesn't pass through or touch an object or effect that blocks vision - such as a stone wall, a thick curtain, or a dense cloud of dog - then there is line of sight.