Mostly I'm doing this cause I've never tried lava before. Beyond that, I think I'm going to need to do a lava filled map soon so I wanted to figure out my process a bit.
STEP I - Google Up Some Inspiration
I spent a lot of time looking at lava flows, and then remembered how the Balrog looked in Lord of the Rings and googled him a bunch too. With those images firmly implanted in my mind, I proceeded to open up Photoshop and leap into step 2.
STEP II - Bottoms Up
I usually do my maps starting with the floor and working my way up, so I figured I'd start with the lava.
New Layer > Fill it with black
Filter > Render > Difference Clouds > Hit Cntrl-f about a gazillion times.
Right about now you should have something that looks like this:
Large spans of twisty white will probably be important since those will end up being our highlights. Make sure you've got a fair bit of those.
Repeat the process on a new layer so that you end up with two different twisty, cloudy things.
Go to the top layer and set it to Overlay.
Futz with the contrast of that top layer till you get a nice even spread of swirly madness.
Hot hot hot! Cntrl-b brings up the Color Balance window. Play with the red and yellow levels in the shadows, mid tones, and highlights in each layer.
Now we have lava.
STEP III - When I Get Back on Solid Ground
New layer! > Fill it with black!
Filter > Render > Difference Clouds > Hit Cntrl-f about half as many a gazillion times as you did for the lava.
This is what mine looks like:
Now, go to the Channels Window, and drag one of the channels down to the new channel icon
Then, go back to Layers
Make new layer > Fill it with a nice mid-range gray
Filter > Render > Lighting Effects
Which should leave you with something that looks kinda like this:
Hey that looks like rocks!
STEP IV - Roman Numerals Are Pretentious
So. At this point, if you've been following directions, and as long as I didn't screw anything up, you should have 3 layers. One layer of rock up on top, and two layers of lava underneath. Now comes the part where we poke holes in the ground and let the lava through.
Select the top layer (the ground layer) and click on the Add Vector Mask button.
It's that little square with a circle in it button on the bottom of the Layer window.
Now, to explain what a vector mask is doing, everything in the mask that you paint black, will show what 's underneath that layer. Everything that's white, will show the layer that you're on. You can get the same effect by erasing the layer you're on, but the mask isn't destructive. You can go back and forth, painting things black and white, and you never have to worry about losing something important.
So, make sure you click on not only the ground layer, but the vector mask on that layer. Select the paint brush (I'd suggest a smaller brush, with a soft edge, and a paint opacity of about 50%) and start painting out the spots where you want to see lava.
So there's a quick run-through of at least my first attempt. The one thing I thought was really neat about pictures of lava flows and fields, which I didn't manage to capture with this run, was the sense of movement to both the lava and the cooled flow. We'll see what I end up going with.
