We will begin with a look at the model itself. Its always good to unwrap Uvs on an object that is not to detailed because it can get difficult to edit quickly and I am going to be using UVlayout which automatically smooths and unwraps a models UVs and it can get very slow if there are thousands of polygons to unwrap.   The model is split into three parts, I decided not to have the mandible as a separate object from the rest of the skull because it can be easily split up in UVlayout. The teeth though are separate because they will make a lot of UV shells and its best to have them separate from everything else.

In figure two it shows the model being imported into UVlayout, in the “load options” the “new” box is checked, this clears any previous Uvs that are written into the .obj file. If the “edit” box is checked it will import any Uv’s written into the file so you can edit them.

The next thing to do if the object is symmetrical is to tell Uvlayout to find its symmetry, this helps a lot because it mirrors over any cuts you make to one side and when it unwraps the shells it makes both sides match. This can be seen in figure 3, also I have split up the mandible and main skull object.

In figure 4 I have spent a little time cutting up the model into chunks that can be easily unwrapped, the trickiest area was around the side of the skull. It can sometimes take a while to get these things right, there was a lot of back and forth with cutting up parts and seeing if it unwraps well, and if it didnt unwrap well then I made adjustments and unwrapped again etc.

In figure 5, it shows the process UVlayout goes through as it unwraps the UV shell. It can sometimes take a few minutes depending on the polygon count of the object. you can see I let it calculate a little too long and there are overlapping UVs near the face of the skull, I fix this later. Also notice that with symmetry on the UVs are identical on each side.

It didn’t take too long to unwrap the rest of the shells. You can see in figure 6 in some of the UVs there are some areas of blue or red, this means that areas with red aren’t getting an equal amount of UV space in comparison with all the others UVs, and blue means the polygons are getting too much UV space and green of course means the polygons are getting the right amount of UV space.

In figure 7 I have imported the Uvs back into Maya and applied a “UV display” texture to it. This allows me to easily see on the model if there is any pinching of the UVs or any areas of weirdness.

There are some areas that need adjusting on the mandible. I mainly use UVlayout as a tool to make UV shells, I do all my relaxing and adjusting back in Maya. This is shown in figures 8-10. My technique for relaxing UVs in Maya is to use its “Unfold UVs” tool. I found the best way to use this tool is too use its “unfold constraints”. This means when I relax the UVs it only allows them to move either vertically or horizontally, when I use this tool without “unfold constraints” I sometimes get undesired effects. I unfold vertically and then unfold horizontally.

As you can see in Figure 10 the “unfold UVs” tool has performed perfectly at eliminating any “UV weirdness” on the Mandible.

The next place to fix are the orbital sockets shown in figure 11. Areas like this can be very tricky to unwrap if only a single planar projection is used. I found the best way to improve upon this area was to use two planar projections on the Y axis.

Figure 12 shows what I mean, It effectively turns UVing a bowl shape into Uving something less rounded which will get less distortions. Though for some shapes its just not possible to get an absolutely perfect UV space distribution without a lot of seams.

As you can see in figure 13, I welded together part of the seams on the orbital sockets, this makes it a little easier to texture if only photoshop is being used but luckily these days 3d projection painting in applications like bodypaint are used to paint over seams.  I also like to make the UVs resemble the model as much as possible, this makes it so much easier to make textures for it.

As you can see the UVs for the orbital sockets have been improved quite a bit. Almost done now with the general editing and relaxing of all the shells, I went through to all of them and used the “unfold UVs” tool. I needed to quickly put it back into UVlayout and edit the main skull UV shell with the overlapping parts.

It normally doesn’t take me long to make these adjustments, After a lot of practice at Uving things I get an idea in my head of what probably needs to be done to fix any issues, there isn’t really a huge variation of UV problems and if you can fix one thing its pretty easy to fix another.

Now the final step is to arrange all the UV shells into the UV grid so they can be exported and texturing can begin. Maya has a fantastic tool called the “layout” tool. This takes the UVs of an object or many objects and arranges them in a tidy way. It also scales all the shells in relation to each other. This is important because it means the UVs for the orbital sockets wont get more UV space than the mandible, everything gets an equal amount of UV space for its size in the “3D world“.

The layout tool did a great job of scaling everything and making it fit within the UV grid but doesn’t always arrange the shells in a good way for texturing. I always go in afterwards and arrange them the way I want, this makes texturing easier if everything is arranged in a logical manner. I also added the teeth UVs to this as well. They were very simple to unwrap, I simply put them into Uvlayout all as one object and then split them up. I gave them quite a bit of UV space for their size in relation to the rest of the model, the teeth is something that people like to make detailed so its good to provide them with enough UV space.

That’s pretty much it. I hope you learned something from this, more tutorials are coming.