Visibility radius is a game mechanic - so lies outside the remit of this as a game agnostic mapper. But GM settable hard and soft FOW should make it easy enough to set this appropriately.

Here's the version I have in production now:
Click image for larger version. 

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Click image for larger version. 

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One is the GM view (so you can see what is/isn't in FOW), the other is the player view.

And if you want to try it out, sign up here! https://docs.google.com/forms/d/1G7y...4CGt4/viewform