I have lost a little of my material room knowledge but I need to try to combine three parts  of a texture into one diffuse. I have the base skin texture and I want to add a scar layer in a certain color (call it red) and then I want to add a hair layer in a certain color (call it black). If I could get a touch of assistance with the blender nodes I would appreciate it. I have an older file someplace that I do something similar (beard and superhero outfit on top of diffuse) but I can't find it on my other machine.

Thanks, in advance.

a simple way is to use two image files and a mask.  You may be able to omit the mask.

add a blender node. connect the two image maps to inputs 1 and 2 . set the blend value (last input) to 0.5 and connect the blender node to diffuse.

The blend value can be adjusted as needed.

For better blend control make a black and white mask and plug it into the blend value input.  The mask sets one or the other image to display. Blur the edge of the mask a little and you get a transition between the two textures.

Thanks. I was doing that but it was coming in half as strong as I wanted but I adjusted the strength of the initial blends and it worked, if somewhat inelegantly.

try a search for tatoos in this forum. There are a couple ways of doing it. Bagginsbill is the expert.

Actually, it didn't work as well as I had hoped. And yes, I haven't seen him around much lately. I know he is busy :)

You can also use a color_math node set to multiply.

If you put the map of scar material on white background, when you multiply the two images, the white will drop out, because anything times 1 is unchanged.

http://www.renderosity.com/mod/forumpro/showthread.php?message_id=3093638

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2716576

these two threads might help.

You might also get an interesting depth effect by blending using a Custom_Scatter node.  Not sure how well that would end up working for skin and tattoos, but I've had some success at creating layered depth for other surfaces using that node.  Putting the tattoo in the base layer might allow one to skip any blurring step, dunno....  :unsure:

     If you have two textures in addition to the base skin, I would suggest a red/green/blue mask on a black background. The black background of the discriminator image would represent skin. Red can be scar, green for hair, and blue unused. Component nodes for each color would drive the value of that color's texture.* * A chain of blender nodes creates the composite texture.

.

The mask, the displacement map, and the "Blinn" map, are automatically created from the second "corset" texture".

Figure texture is upper right
Second texture is lower right
The Blender puts one on top of the other, controlled by the in Math_Functions_3 automatically created mask.

The Blend value connected to the mask on the Blender node should be 1.  Anything less lightens the combination. 

Thanks all. I got it figured out.