Left: happy UVs; Right: sad UVs
In a previous post I’ve detailed what makes a UV map good. Now I’m going to actually show you how to make a good UV map through proper use of symmetry, uniformity, and logical seam placement. Here is my workflow :
1. Know what things will repeat or have symmetry beforehand! If a face is symmetrical, delete one identical half before making you UVs. Then when you mirror the mesh to complete the face, the UVs for the left and right half of the face will share the same UV space. This will save valuable texture real estate and increase the fidelity of your model. Repeated elements (i.e. fingers) should share UV space as well, no element should need to show up on the texture twice.
This character has a lot of symmetry, so parts had to be deleted before mapping
2. Start with an automatic map. Select the whole model you intend to texture and go to Create UVs > Automatic Mapping. This will give you a starting point, and most importantly it will lay out all of the UVs you have not mapped so that you’ll know if you missed any.
3. Use planar mapping for everything. Select a set of faces that roughly share a plane and use the “Best Plane” option under Create UVs > Planar Mapping, then project. In the attribute editor for the projection you just created, set the projection width and height to 10. This way you are basically flattening out your model’s skin to make it easy to paint on, and you are scaling them all by the same factor so that each part will be correctly sized in relation to the other parts.
It is ok to use the cylindrical mapping tool for cylindrical elements (like fingers), just make sure that you keep the scale uniform and don’t make any unnecessary seams.
note: I typically place the UV’s I’ve projected in the 1, -1 (lower right) quadrant while working on them, so that I know that anything in that quadrant is done and anything in the 1, 1 (upper right) quadrant is not. If you do this, make sure that you move everything to the 1, 1 quadrant when you’re done or you might get errors.
I projected faces on this section of the foot based on how well I though I could paint them from that angle
3. Move and sew edges of UV shells where you don’t want to have seams. The most important idea in this step is that you want to group together all of the UVs that share a material if possible. This way you can more easily paint the object in 2D and you don’t end up with any awkward seams where there should be none.
connecting two UV shells using 'move and sew UVs'
4. Make it fit as tightly as possible. Now that we have all of our UV shells sewn together and uniformly scaled, we need to fit them into the UV square efficiently. You can do this by moving, rotating, and mirroring your shells (scaling by -1 in the x or y), as well as by uniformly scaling all of the shells if you find that there is not enough (or if there is too much) space.
note: It is ok to scale some elements down further than the rest if you know that they either won’t be seen or won’t need any detail other than a flat color.
The bottom of the character's foot is almost never seen, so I can afford to scale down its UV shell
If you follow these steps, you should end up with a very efficient, paint-friendly UV map. Keep in mind there is no fast or easy way to lay out UVs for a complex low-poly model, but if you follow these steps, at least you’ll do it right.
Stay tuned for next week’s post, where I’ll talk about my texturing workflow.