Gotta start somewhere, eh? Well, if you are a Displace rookie, I'm a bit apprehensive 'bout posting how to make the D-Map. Following directions is one thing. Understanding what's going on so you can do it again with out instructions, or reworking it for similiar application, is another. Know what I mean?
Even though I'm late, vector is better, and I'm apprehensive, here goes anyways.
Start a new document. Minimum of 256x256.
Lay down a bunch of guides so you can drag from side-to-side and top-to-bottom with authority.
Grab the Gradient tool and make sure that Smoothiness is 0%. If Smoothiness is not 0%, then you will get Funkiness. Remember: Smoothiness and Funkiness are directly proportionate.
Default colours: black and white by slapping the 'd' key.
Linear Gradient.
Drag it so white is across the top and black is across the bottom.
New layer.
Reflected Gradient.
Drag it from the center to one of the sides so that white is down the middle and black is on the left and right sides. You might have to flip the 'd'efault colours, but I can't say for sure.
Set the mode of this layer to Exclusion.
Add a Curves Adjustment Layer.
While the Curves Ad-Layer dialoge is open, bring the lower-left point up to 128. Add another point and drag up so you have a semi-circular/oval kind of looking curve.
Slap the 'Okay' button to get out of the dialoge. I call this Ad-Layer 'Tweak'.
Clip the Curves Ad-Layer to the Exclusion layer.
Save as a PSD to be used as a D-Map.
Get busy with Displace using Horizontal: 0%, Vertical: whatever positive%, and Stretch to Fit.
Don't like the resulting curve you get when you Displace? Go back to the D-Map and tweak the 'Tweak' Ad-Layer. Or try different Vertical: whatever positive% to bring the curve in more or less. Hmm... more or less... something like that. I'm sure you know the drill.
:whew: