Quote - Actually if you make two versions of your pattern, one horizontal, and one vertical, as shaders it is easy.

You then plug them both into a Blender.

You make a mask for where you want pattern 1 = black, pattern 2 = white.

You drive the Blender.Blending value with that mask.

So all you have to do is design a good pattern for the arm that is bad at the moment - using different mU+nV to get a good line. (I assume you used m=1, n=0 for the existing case that is mostly horizontal)

Once you have the new pattern you combine with the old one using the Blender and mask. This is similar in technique to a transmap - the math is identical. The only difference is we treat one pattern as the "background" and make the other pattern the "transmapped" texture on top of it.

But I call this a blending mask.

Photoshop would call it a "layer mask".

That's exactly what I was trying to describe.  A way to simply incorporate both materials using a mask to separate them from being displayed on the wrong regions (over each-other).  It's done with textures all the time and is easy to do.  (Tatoos/second-skin clothing, etc.)  I didn't think the principle was any different with generated materials with the exception of having the engine compute the materials on the fly which would have to be adjusted for the different regions.

I don't know a lot about Poser's material room but it seems relatively straightforward.  I just haven't played with it enough to learn to develop good techniques.