About LOS Checking

VASL provides an integrated tool you can use to check line of sight (LOS)

Version 6 and later boards support LOS checking. All MMP and BFP geoboards (including SK, Deluxe, and a/b style boards) along with several others support los checking. Most HASL and TPP boards do not but RB, RO, Dinant, and Singling do. You can flip and crop boards, either to half-hexes or full-hexes and LOS checking will work.

LOS checking can apply ETO terrain rules or PTO terrain rules. As of 2023, many but not all DTO terrain rules apply.
PTO terrain rules are applied when you choose and apply the PTO Transformations option in the Terrain Transformations dialog. The following transformations are available:
  • Dense Jungle
  • Bamboo
  • Palm Trees
  • Swamp
  • Huts

If the Dense Jungle box is not checked when other boxes in the PTO Transformations are checked, woods are treated as Light Jungle.

LOS checking increasingly applies to overlays and terrain counters, but this is not yet complete. LOS checking also does not detect hindrances along a Continuous Slope. LOS checking does not work correctly in board edge half-hexes where abutting half-hexes have different terrain types.

The LOS engine does not enforce the rule that terrain must be visible on both sides of the thread to affect LOS. If the thread touches an obstacle or hindrance, LOS will be affected.