Hi Bagginsbill,

Quote - - This is V4, right?
Are we shading a body suit that is like V4's stupid UV map? (I don't have this item and have never seen it)

Yes, it's V4 and in example her bodysuit from DAZ. I used that cause it has some nice morphs to give the pants and arm sleeve a bit flare not as tight as a pantyhose or stocking.
That bodysuit has a compltely different uvmap compared with V4 ... especially regarding the legs and arms. Legs are 4 pieces left/right as back and front. Back an front match exactly there the lace now is placed. So that makes the additional problem that the back and front side of the lace are on 2 different pieces in the map. Makes it more difficult to have them right matched.
As said I'm not such a great texturing specialist.

If my 2D skills would be better I might never have come to 3D ... buildings, cars, technical drawings as also trees or birds ... ok ... but something looking like human beings, even if aliens,  no, no,  better to have 3D to make 2D images ...

But back to theme, morkonan, who is building that moonbase jumper might use the shader on the V4 as a second skin.

So my idea was to create something that might be used on the bodysuit (or other clothing) with a bit transparency but on other hand could be used also as material for a second skin without transparency.
As far as the fabrics without that lace it works very well.

So thinking that the uv's might be different I needed something to set the correct position of the lace depending of the carrying figure. That was the base idea to combine a uvmap for that part with all around as procedural.

If you see my map (didn't know that I mentioned somethere to include the complete uvmap ) that black lines are round 20 pixels (back and front) in total and the underlying polygons are only 5-6 in total parallel along that lines. So there is not much volume to do something.

Quote - - So procedurally we can do it, but the UV axes don't line up. And there is a discontinuity in UV coordinates between upper thigh and lower thigh, as well as a huge abrupt change in UV density. Am I understanding the problems or off base?

Additional direct in the middle, e.g. exact the border of the uvmap, is a straight seam that can be morphed to be seen in the figure. That's cause it looks as if the fabrics isn't right fitting even if the uv is matching front and back. But thats not a problem, needs only to morphed zero to go straight.

Quote - -The side lace-up looks like it could be modeled as a separate conforming clothing item, just a strip up the side of the leg. It seems to stick up from the rest of the legging. You could model that with a good straight UV map and just apply a tiled image of the lace only.

Modeling as a conforming clothing is for sure a good idea and if it would be for Posette it would have been my first ... but V4, uh, why does she have so much morphs and magnets and other memory killers ...

Quote - - Or what about re-mapping the legs altogether first?

It should be a most simple solution, also I think remapping would not solve the problem with view to versatility of such a material.

Quote - - Never mind I find the BS-LegSeams.jpg file. So the UV seams are actually right there on the side of the leg? Wow that's doubly complicated.

Yeah, they are on position.

Be coaxed :thumbupboth:  Knowing your talents from several postings I would not have bothered you if it's not challenging ... 
I often had colleagues that in front of looking to a problem and trying to solve first asked for some training curses. Not my way ... training on the job is the better solution. What can be done should be tryed ... but, ok, than might be a point there it is better to ask a expert as to waste time and energy on a might be misleading way ... so here we are ...

Quote - - I have an idea about using a piece-wise linear function to track the seam, and use that to "straighten" and "expand" the UV map.

Hey, that sounds good ... though I have no idea how this might look in source ...

But this will also need a 2D map to find the correct position, right ?

See, I didn't see any solution to place a procedural shader on a specific position if it's not a mat zone as such. Ok, there is a function to get exact x,y,z-positions but only in viewspace. So I looked desparately for such function giving that point on a figure.

That fabrics material for example is derived from a stripy material I have created for stockings of the "Pippy Longstockings"-type (in german Ringelsöckchen). And there my first approach went over that x,y,z space component with the problem that the material didn't follow the clothing.

So then went over to that u-v-components but they don't give any chance for a precise positioning in the mat zone or did I overlook something.