perfect-vision VS foundryvtt-drag-ruler

in foundry v10 you can do that with the module perfect vision which can set up areas where global illumination is disabled, alas some change in foundry v11 make updating the module too complicated for the author so he abandoned the project

You can use the module Perfect Vision to draw areas of darkness, limited vision etc.

Perfect Vision v4.1.14 Bugs URL

Look no further, perfect vision does exactly what you want to do: https://github.com/dev7355608/perfect-vision

Have you checked out Perfect Vision?

Perfect Vision v4.0.17 [Bugs URL](https://github.com/dev7355608/perfect-vision/issues)

perfect vision lets you do this with their vision limit setting in a drawn shape

Clicking on a drawing you should see a lighting menu like this https://github.com/dev7355608/perfect-vision/blob/main/images/drawing-config.png

Alright, this isn't a direct answer to your question, but more of me trying to answer what I think your problem is. I believe the solution is using https://github.com/dev7355608/perfect-vision

Perfect Vision: Improved vision support

foundryvtt-drag-ruler - his module shows a ruler when you drag a token or measurement template to inform you how far you've dragged it from its start point. Additionally, if you're using a grid, the spaces the token will travel though will be colored depending on your tokens speed. By default, three colors are being used: green for spaces that your token can reach by walking normally are colored green, spaces that can only be reached by dashing will be colored yellow and spaces that cannot be reached with the token's speed will be colored red. If you're using a gridless map the ruler color will change to convey this information.

Drag Ruler v1.13.2 Bugs URL

Drag Ruler: https://github.com/manuelVo/foundryvtt-drag-ruler (requires socketlib)

Drag Ruler - Allows tokens to display a ruler indicating how much they are about to move. Can create waypoints to make a token move between multiple destination points.

I've just released Drag Ruler v1.13.0, which is the first official Drag Ruler version to support Foundry v10. A lot of code had to be changed for this release, so it's quite possible that some bugs have crept in that weren't present in Drag Ruler v1.12. If you find anything, please report it in the Drag Ruler bug tracker.

The module uses Drag Ruler iirc as it's source of measurement. Drag Ruler does not work with V10. There is an interim update (not released by the Drag Ruler author) but not sure if it works with ETL

Drag Ruler: Ruler display on movement

Drag Ruler