During this modelling task, we also had to UV map the objects in the scene.
I have never really UV mapped before, therefore, had to have a look into it.
I found really good series on Digital Tutors, which explained the basics behind UV mapping, and explained a bit about why we do it.
The UV Map- the process of bringing the 2D and 3D together.
So, UV mapping is the process of putting a texture from a 2D object onto a 3D one. It is the resolves between applying a texture in a 2D space, to one in a 3D space. UV’s act as a bridge between both 2D and 3D. In the maps themselves, each vertex is assigned one UV. The UVs themselves need to be evenly distributed, otherwise they show distortion. A way to check this, is by using a checker board texture (in Maya).
Another thing to keep in mind is the seams- or were the pieces of the UV map join together. These are normally kept somewhere they are hidden, or occur naturally, like on clothing.
Basics of UV Mapping
In the UV editor, there is a viewport. There is a U and a V direction in the part where the texture is displayed.
The UV editor view.
The tutorial explained that the easiest way to map this cube, or simple objects like it, would be to cut along the seams and lay it out flat. Seams are the areas were the UVs are disconnected.
Planar maps are normally used when there are a lot of flat parts in an object. To do this technique, you would open the UV editor and select the options box on the planar mapping box. Selecting the faces you want to map, you then select which axis these faces lie along. In the options above you select the below if;
You are mapping an entire object- us bounding box
You are mapping just selected faces- select best plane
After the faces are mapped, then you have to fix the cubes until they are undistorted/ not stretched. Once this is complete, in the UV texture area, click on the corner of a few of the vertexes and shift select shell. You can now rotate it to the correct orientation in the UV texture editor, and scale it to fix the distortion.
In the example in the video, the locker object, there was some distortion in the way some of the UVs were laid out, at an awkward angle. For these, the axis to project would be “fit best plane.”
Mapping awkward planes.
Any objects with square sides or regular shaping, you can select “keep width/height ratio.” This keeps the ratio to the area mapped.
Spherical and Cylindrical Mapping
The example used to map here was a microphone. The tutorial started with the middle part, selecting the cylindrical map. Then, like before, adjust the size of the map so there is no distortion.
The top of the microphone used spherical mapping. It can be edited horizontally and vertically to achieve the correct UV map.
After this is the process of cleanup- cutting the geometry to ensure that the map isn’t smashed together.
Cuts need to be made along the top of the map to prevent stretching.
In the menu set for automatic mapping we have to focus on the planes, which the amount of projections used. Using 6- this makes it seem like a cube, a projection from each side.
Selecting the right amount of planes.
One this is mapped, it should look like this. The next step it so rotate the pieces to the correct orientation. The next part will be to fix these pieces together, to form a better map.
Before concluding, the tutorial showed us what difference altering the plane number would have. Increasing to 12 created more shells, however, this would result in less of a distortion.
The automatic map of the face.
Editting UV Layouts
To start laying out the UVs, we must shift select the shells and move them to the LHS of the UV editor. We then arrange some of the UVs that are easiest to recognise that fit together.
Laying out the shells that obviously go together.
Instead of using the sew option (it stretches the UV) we have to use a different tool to join them to create the look below.
Sewing shells together again.
Once the pieces are sewn together, there is a lot of overlap which occurs. This can be shown more clearly through going to Image- then selecting shade UVs. To stop this, you have to unfold the UVs.
Overlapping UVs are evident.
Unfolding the UVs.
Continue this process of attaching the UVs and unfolding them, to remove the uneven spacing (shown in areas around the eyes).
Once this is completed it should look like this;
Relax and Unfolding UV’s
Some of the UVs are not yet evenly spaced, and so we need to edit them further.
In the relax UVs button, set max iterations to 5, and tick both the pin UVs and the pin borders boxes. Once applied, it evens out the UVs.
I will use all these processes myself when UV mapping my own assets.