I saw some pictures of M4 with the veins of the body visible.

can anyone tell me where to find the kind of skin ?

thanks

Do you actually mean visible or prominent?  If you are referring to 'popping out', then there is one product for sale @ DAZ3D.

http://www.daz3d.com/i/3d-models/-/m4-displacement-maps?item=8356&_m=d

However, it only works for DAZStudio..

There is a freebie script which will accomplish the same effect @ RuntimeDNA.  Developed by Semidieu, and it can be found here:

http://www.runtimedna.com/forum/showthread.php?40908-M4-Displacement-Not-only-for-DAZ-Studio&highlight=m4+displacement

The displacement maps from DAZ link Hborre gave you are .tiff files.

I used 'em by manually attaching the .tiffs to the displacement plug.
with displacement values of .5, 1.0, etc.

Wich is the "displacement plug" ?

many thanks

That is a plug connection on the PoserSurface node in the advanced section of the Material Room.  Currently, I am not at my own computer, so I can't give you a screencap of it's location.

Dear hborre, can you help me again with better information about "displacement plug" ?

Many thanks.

The image above shows a screencap to the advanced tab of the Material Room.  Notice, specific areas are encircled in red to make it easier to identify when you look into your own application.  The large node entitled 'PoserSurface' is your primary node for either your character/prop or material zone for the aforementioned objects.  This is your control center, so to speak, where various maps, specialty nodes, and mathematically derived combination nodes are plugged in and dictate how your textures are going to respond to your scene lighting and render. 

For your particular query, ignore all the other connects in the image and look down the PoserSurface to where Displacement is encircled.  Look to the right of that plug and you will notice a wire connection attached to a set of nodes.  In this instance, we have a grayscale Displacement Map connected to a Displacement Bias, in turn, connected to Displacement of the PoserSurface.  This is not always the arrangement, displacement maps are usually darker and not connected to bias nodes, but I am just illustrating a point. 

By increasing the increment values on the PoserSurface Displacement dial, you can add varying degree of mesh displacements to your texture to enhance its appearance.

In the image above, I dressed up my M4 in a converted texture I downloaded from sharecg.com.  This was rendered without any displacement.  Notice how smooth his overall appearance came out.

This next image illustrates how activating displacement in your render settings and applying a Displacement map to the character dramatically changes M4's overall appearance.  This is Semidieu's free M4 Displacement script applied.

You can never see displacement occur in the Preview window, you must render to see the difference.  Also, displacement must be activated in Render settings for a full effect.

Forgot a little thing ... The displacement bias is a substract math fonction ...

Value1 set to 1 and plug your map
Value2 set to 0.5

Many thank Anthanasius

but i'm not able to find the way to add the different node in your image....

Like this ...

Ok, that's work !!

Many thanks to everyone.