Texturing With Blender

This tutorial shows how to apply texture coordinates to a mesh. Your model should be finished. All unnecessary vertices should be merged. Every future modification of your model will destroy the texture coordinates of the affected faces! We will use LSCM, acronym for Least Squares Conforming Map, which is one of the algorithms for unwrapping a mesh onto the 2-dimensional UV space. It is a very powerful unwrapping method because it can preserve the shape of each face very good.

Marking the Seams

Go into Edit mode and activate edge selection mode with Ctrl + TAB. To map the model to a 2-dimensional UV space, you will obviously have to make some cuts in you mesh. This is how you tell Blender where you want to make cuts: Select the appropriate edges, press Ctrl + E and select "Mark Seam". The edge will turn orange, an indication that it has become a seam. If you change your mind, select the edge again, press Ctrl + E and choose "Clear Seam" to remove this seam.

Try to find a good balance for the number of seams: many seams will reduce the deformation of the faces a lot (which is good) but it can be quite tricky to create a texture for it, because you will end up with a lot of small parts of your texture (which is bad). However, it is always a good idea, to make seams where the model has natural borders. You could separate an aircraft or spaceship into wings, engines, weeapons, cockpit, gear and hull, for example.

Unwrapping the Mesh

Before you can start unwrapping, you will need another window. Split the 3D-View in the middle by clicking the middle mouse button at a border of the 3D-View. Select "Split" and split the window in two. Set one window type to UV Image Editor with the drop-down box on the left or with Shift + F10. You should now have a 3D-View window and an UV Image Editor Window, in which you can see the UV plane, where the UV map will be laid out. Inside the 3D-View Window hit F to toggle UV face selection (this mode is another mode like Edit mode or Object mode). Your model will most likely turn completely white, at least if you have never tried to unwrap it before. Select all faces of your model with A, hit U inside the UV window and then choose "Unwrap" to use the LSCM algorithm (Blender ≥ 2.42). Now you should see your unwrapped mesh in the UV window.

If you have a very complex mesh, it may be better to unwrap your model in several small steps. Select only the faces, you want to unwrap instead of all. When you are finished, ensure that you really unwrapped all faces.

Modifying UV Layout

Right now, your UV face layout looks probably pretty weird. Your next step will be to optimize the layout. Try to use the full UV space, that is available and reduce deformations as much as possible. The layout out behaves pretty much like objects in Edit mode: the parts can be dragged, scaled and rotated. Two other useful functions are the following:

• Align/Weld: Use this function to align a group of vertices in 1 or 2 dimensions. Select the group of vertices and hit W. This can be useful to beautify parts, that have been deformed by the unwrapping process.
• Pin/Unpin: You can pin vertices with P. These vertices will be left untouched by the unwrapper. Using this, you can unwrap a part of the mesh, pin the vertices that have been unwrapped without too much deformations and then unwrap the same faces again to improve the accuracy of the shape. Vertices can be unpinned with P.

Paint the Texture

Now that you have laid out the UV map, it is time to create a cool texture for it. First, export the UV face layout from Blender as a tga-file by selecting "UV" → "Scripts" → "Save UV face layout" in the UV window. Ensure, the dimension of your texture is a power of 2.

The tga-file is the pattern for you texture. Open it with your favorite 2d graphic editor and start painting. The pattern can be used as background image. When your finished, export your texture as png- or jpg-file. Sounds easy, but what is written here in a few lines can easily take ten hours.

Apply Texture to Mesh