I have no idea how the code determines lighting, so I apologise if any suggestions are nonsense or unimplementable.
Personal light sources can have a bright and dim light radius, such as the default D20 lamp:
Lamp - 15: circle 15 30#000000
In the following image, Vision is set to "Night", Fog of War is enabled, and the character on the left is a human with the default D20 Lamp.
- Light and sight example.png (105.94 KiB) Viewed 2706 times
The character on the right is an elf with the default darkvision:
Darkvision: circle r60
The Elf's can "see" like the "bright" part of the light cast by the lamp, rather than the "dim" outer edges of the lamp's radius. I imagine since there is already code to cast bright and dim light with light sources this could be implemented without significant changes for the "personal light" associated with sight? Having the ability to define sight bright and dim radii (as for light sources) would help to overcome any D&D/Pathfinder/etc specific problems).
Just to see if it would work (in case this had already been implemented but was undocumented), I tried changing the Campaign Properties->Sight setting to
Darkvision: circle r30 60
(this caused Java error popups)
or to
Darkvision: circle r30 r60
(MapTool automagically removed the "r30" when I closed the Campaign Properties window).
I certainly get that implementing black and white vision, and dawn/twilight modes would be a significant extra piece of work so am certainly not pushing you for those!
Thanks again.