How do I create a nighttime variant of a battle map?

[rogue_gamer]

How do I create a nighttime variant of a battle map? I'm guessing it has something to do with adding overlays and using the eraser tool. If there is a good tutorial anyone knows about I'd love to be pointed in the right direction.

[Redrobes]

Quick and dirty would be to take a copy of the map and erase it all to black. Then copy paste that black one onto the map as a new layer and do a 50:50 blend. Then on the black layer spot in with a white blob wherever there is lights like bonfires or lamps etc. Then blur the black with white blobs layer a lot so all of the white spots are now blended blobs of lightness. Then use contrast or the color curve tool to make the black and white layer more grey than black by raising up the black level to a mid to dark grey sort of value. Then change the blend mode of the layer to "multiply" and set it to 100% instead of the 50:50. Then all of your map is darker but with all of the light areas lit up. You can also play around with adding in yellow instead of white on the black layer if the light is a candle or fire of some sort. Or maybe aqua or green if magical light etc.

Sometimes people go for a generally navy blue base rather than darken with black / grey. Not sure why tho.

Clearly some activities change at night and maybe the whole map needs some rework but as I say thats a bit quick and dirty to get you part way there.

[RenflowerGrapx]

Well, i'm one month late on this reply, but... I do battle maps for a living and I have my method for the night variants.
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What I do is to apply a "multiply" layer in a cold color. Which is between a blu-ish and purple-ish shade. Depending on the ambient.
and ABOVE the dark layer, I apply a light layer in "screen" mode. This Light can be pink, yellow or orange, (at your taste, it can be really any color)
I apply a Mask on the light layer, and paint on the mask the sources of light, the reflections (if any), and the ambient fade.

This method allows you to edit the colors of the light and dark area without ruining your original art. Plus, you can play and create multiple layers to change the light effects.

I don't know any tutorials, but I have a couple of battle map speed paintings in my youtube channel if it helps. They are more about the full drawing/painting, I don't show the layer panel, tho.