Improving unwraps
Our new tool is located in the Overlays tab of the UV Editing area. You can see the Overlays tab open in Figure 4.45:
Figure 4.45 – The Overlay tab
In this tab, we can scroll down to the Display Stretch checkbox shown in Figure 4.46:
Figure 4.46 – The Display Stretch option
With this setting, we can check two things: the area of the individual faces, and the amount of deformation each of the faces has. By default, it checks for the angle, but this can be changed in the Overlays tab we just used to enable the setting. With this setting set to Angle, we can see how it affects a cube in Figure 4.47.
Figure 4.47 – Affected cube model with new settings
Notice how all of the faces are blue. This means that there is no warping because all of the faces are being warped from how they are actually shaped on the mesh. Notice how if we move a point on the mesh, or if we move a vertex in the UV editor, the UV map starts to turn green, and then red on the vertices it is affecting. Figure 4.48 shows a vertex in the UV editor being moved.
Figure 4.48 – Moving a vertex in the UV editor
This can be corrected by either moving the mesh or the UV map to match the shapes as much as possible. When unwrapping a finished mesh, that usually means tweaking the UV map. This is often a good indication of whether you have enough seams on your UV map, or whether you have them placed well enough. If you unwrap your mesh and there is a dramatic amount of warping, you will likely have to change your unwrap.
The final thing you want to think about when unwrapping your model is something called texel density. Texel density is the size of the face in relation to how much space it takes up on the texture. If we look back at our pants example, with the separate UV islands, we can see this in practice. In Figure 4.49, we can see the two legs next to each other with different texel densities.
Figure 4.49 – Different texel densities
The leg on the left has a shrunken UV. This reduces the texel density of that leg because it is taking up less space on the texture and, by extension, makes the texture look bigger on the mesh. The leg on the right has an enlarged UV. This increases the texel density and makes the texture look smaller because it takes up more space. This is how you can control what parts of the mesh get more detail than others. Have a higher texel density on the parts you want more detail on, to allow them to take up more space on the texture. This is something we need to control on each of our unwraps, and we need our mesh to have as consistently sized quads as possible to help with this.
Thankfully, if we observe all of our previous topology rules up until this point, our only trouble should be in marking our seams properly, but if you find that you are unable to get the result you want regardless of the seams, it likely means that you violated a rule earlier on.
