How to create displacement maps in photoshop / gimp.

I have met someone who was so kind and explained to me how I can create my own displacement maps, well, at least the simple ones like for example veins. His simple but intelligent tutorial is a start for sure and gave me an idea of how this works, I asked him i I am allowed to post his words here and he is okay with that. So here we go (Some photoshop and / or gimp knowledge plus a wacom are recommended btw.):

"In Daz Studio, displacement maps work pretty much like bump maps. Light areas render as positive while dark areas render as negative. To make a map for veins, for instance, I load the actual texture into Gimp as a guide layer, create a transparent layer above it, and simply airbrush the veins (white) using the texture as a guide. Some textures have veins that are visible and very easy to follow, while others do not and you just have to kinda wing it. I add in a black background behind the vein layer. Generally, so they have a nice soft appearance, I duplicate the vein layer, and run the bottom copy through a gaussian blur filter. This gives an more gradual fading of the edges of the veins, while the top original layer will leave the centers raised nicely.

When satisfied with what I've got, I delete the bottom texture guide layer, merge the remaining layers, flatten the image, and reduce it to greyscale, then you can save it as a .jpg or as a .tif file.

The best way to figure out displacement maps is simply with textures on a 2D panel in Daz Studio. Test out the displacement settings to see how everything looks at different levels. For just veins on skin using a white on black map, I use 100% strength, 0% negative, and depending on how bright the white is and how strong you want the veins, between 0.10 & 0.60% positive. The strengths really depend on the map you use.

If you have a texture that uses displacement maps, open them up and take a look at them, and take a look at the settings they use. (...) The "M4 Displacement Maps" have muscular definition as well as vein displacement, and they have to be applied with negative strength and positive strengths as exact opposites (like -0.50% & +0.50%)."

Thank you Chuck for sharing this with me!

This is a very helpful Tut, Mav. Thanks for sharing.
I'm not an enormous fan of second skins, mainly because clothing does not follow all body contours. I don't know of any material, for a bikini bottom for example, that would hug the curves from hip to hip. A little Bump and/or displacement would help in some cases to add the illusion of 'reality'.
I might have to do a Male. Displaced veins sounds like fun.

Oh yes, they are! Also I have done scars and for second skins, I bet you can get great details if you displace patterns for example... There is clothing which I find too flat for example, so I sometimes use the bump as a displacement map for example and it gets structure like real material has. That does not work with all of them though... You just gotta fiddle with it and give it a try. And doing your own displacement maps and seeing them is aways fun.