How does UV pinning work

daniellooartist

I have seen dozens of tutorials that talk about something called UV pinning. It's the concept that you deselect any number of UV's on a shell's boarder and unfold. This will somehow make the unwrap better.

It has never made my unwraps "better" and a large part of this is that I'm not understanding what it actually does. I do what I normally do when I can't comprehend the internet. Make a random shape, play around with the tool and see if any patterns emerge. The only pattern I've noticed is that unselected pinned UV's don't move. I don't understand how or why this is supposed to be significant or helpful.

I started looking back at my old tutorials. 75% of the time they pin UV's on the boarders. I'm not sure why but I it is a pattern I found. However they don't pin all of them, but only some of them. If they pin some boarder UVs and not all boarder UVs, then we can conclude that certain boarder UV's being pinned give better unfolds than others. Now what makes pinning certain UV's better than others is a mystery.

When do you guys pin UV's? What factors go into determining what UV's get pinned?

slosh

I pin UVs when I want to square edges or retain a shape similar to the asset. Example, If I'm UVing a pair of pants, I straighten the border UVs to resemble the general shape of the pants, pin them, and then unfold all the UVs within them for a nice clean, even, layout. Or sometimes you want the center seam of an asset to be straight so you pin those and unfold the rest. There are various uses for pinning...

daniellooartist

I see what your saying. So the boarder edges just have to make up the general silhouette right? After that I unpin all the boarder edges and the UVs will even themselves out right? I tried that myself and i THINK it's working... I did it on a really simple surface so I'm not sure.

slosh

Well, always look at the model with a UV indicating texture to make sure they look even and clean. I UV my stuff to maximize even layout across a mesh, for easy clean shells to make texturing easier, and to maximize texel density across my whole texture. Pinning UVs just makes certain situations easier while UVing.

Bartalon

Pinning UV's doesn't make your unwraps better, it simply makes unwrapping faster. Quality comes mostly from experience. Use a tool for long enough and quality and speed start blending together.

I have seen dozens of tutorials that talk about something called UV pinning. It's the concept that you deselect any number of UV's on a shell's boarder and unfold. The only pattern I've noticed is that unselected pinned UV's don't move. I don't understand how or why this is supposed to be significant or helpful.

Pinning doesn't have to occur at a border edge, but if you have squared off a UV shell and want it to remain squared, then you would omit those UVs your future unfolding operations.

By pinning UVs you are giving Maya a frame of reference for scale and location. Maya will look at how your unselected (pinned) UVs are arranged and try to put everything else into place according to that arrangement.

Imagine you had a partially completed jigsaw puzzle. These pieces could be thought of as pinned UVs, pieces that already have a good projection which you don't want to move from their place. It's much easier to arrange the remaining pieces together based on what is already there.

When do you guys pin UV's? What factors go into determining what UV's get pinned?

I pin UVs for nearly every shell as I am unfolding them. If I get a good planar projection on a few faces, I pin those undistorted polygons for Maya to use when automatically unfolding the rest of the shell. Everything generally snaps into place this way, and I don't have to spend time stitching hundreds of edges back together from an automatic unwrap.

For meshes that might be more easily textured with squared UV shells, such as tire treads, I will often straighten a single border edge, pin them, and use Unfold on the rest which snaps them into place. From there I'll straighten up the remaining border edges as necessary to square off the entire shell.

After that I unpin all the boarder edges and the UVs will even themselves out right?

If you are pinning anything that has bad distortion, your unfolds will probably also be bad. If you pin UVs with little or no distortion, your unfolds will be much better. Whether your pinned UVs belong to border edges has nothing to do with it.

daniellooartist

Great analogy with the jigsaw puzzle. I've tested this and it everything is working as expected.