Uving an Airplane:

UVs are an additional component that coordinates 3d space with a 2d representation of that space onto a map (known as a UV map). Very simply, there will be a UV point wherever we find a vertex (at the intersection of multiple edges/at the corners of a face).Think of UVs like the city of San Francisco represtented on a Globe. There it is an identifiable place in 3d space and that is the Vertex. If there was a sudden Volcanic erruption underneath the city and it rose up off the globe due to the volcano underneath, we would have to manipulate the vertex since it has moved in 3d space. However the UV is like a representation of San Francisco on a map such as a Mercator or Robinson map. Even though the map is different between these two types, the city itself has not moved based on the way we draw the map. UV mapping will be discussed more in Materials and Lighting. The UVs define space differently from verticies in that that vertex points are manipulated in X,Y,and Z space (think of earth in terms of the larger galaxy), and UVs are manipulated in UV or local space (east-west and north-south).

To paint a unique texture for a part of a model, your UVS CANNOT OVERLAP!! It is our job to create a map that has little to no overlapping.

1. Lets look at how to lay out the UVs for our Airplane to allow us to create texture maps:
   
   First, lets select the plane, and as shown, create a planar map of it from the Y-axis (looking downward)
   
   
   
2. Then, lets open up the UV Texture editor window, which will allow us to edit our map
   
   
   
3. Here is a look at the UV texture editor window, with some buttons you might want to know:

   

   0 to 1 space-This quadrant of the graph that we see in the UV texture editor window is in the top right corner. It represents the positive space on the graph, and is where your UVs should be placed to prevent texture repeat. The other quadrants, as well as the area outside of the 0-1 space can be used to store UVs temporarily while laying them out, and then must be moved back inside the first quadrant of the graph.
   
   cut uvs-This function is used to seperate UVs that have been sewn together so that the faces adjoining them can be independantly positioned and moved.
   
   sew uvs-This option is used to connect two parts of the same uv that have been seperated by the cut uvs function or by mapping.
   
   relax uvs-To automatically untangle and even out UVs distribution based on the geometry and the UV borders. Selecting target UVs (one sample is enough) and click the tool (Check Options!) to relax UVs. You may need to repeat this action to see the desirable result. Under the options, make sure to set Edge Weights to World Space instead of Uniform.
   
   move an sew uvs-To merge UVs by selecting polygon components edges, vertices, faces, or UVs. To avoid un-necessary stretching caused by Sew UVs, use Move and Sew UVs instead. Number of vertices does not equal to number of UVs. Be conservative with the amount of UVs for game models. Sew as many overlapping UVs as possible.
   
   align uvs-To align / straighten a roll of UVs. Selecting target UVs (minimum 2) and click the tool (Check Options!) to align UVs.
   
   split selected uvs-Will split all selected UVs into one UV for each connected edge.
   
   rotate uvs-Will rotate selected UVs clockwise or counter-clockwise. Select the target UVs, and click the tool.
   
   flip uvs-Use these options to flip the UVs of the selected faces either horizontally or vertically. Horizontal is the default Direction. Open the option window (click the box beside Flip UVs) and leave it open. Select your UVs and choose the axis which you wish to flip by.
   
   UV Snapshot -When you're finished laying out your UV map, you need to make a snapshot to use as reference for painting the actual image. Make sure all UVs are within the top right corner boundaries of the UV Editor and then (see 0 to 1 space) , in the UV Editor, click "Polygons > UV Snapshot". Define the output location, the resolution you'd prefer (256, 512, 1024, resolutions with the multiples of 2) and the file type. You should have a nice wireframe image in the output directory after you perform the operation.
   
   

4. Lets cut this plane in half. Select a continuous loop that bisects the wingsby double-clicking
   
   
   
   
   
   
5. You may need to manually edit the edges that you have selected:
   
   
   
6. Then, so we can see what is going on, lets display our Texture Border Edges:
   
   
   
   
   
   
7. Cut your selected edges:
   
   
   
   
8. In the UV texture editor, we can now select a UV by right-clicking and choosing UV from the marking menu. Select 1 point.
   
   
   
   
9. We can then convert that 1 point into the whole UV shell:
   
   
   
10. When we move the shell outward with the Move tool (w), the shells no longer overlap. Now we can paint Unique textures on the top and bottom. But there is still plenty of parts that are hard to paint on, like the tail fin, and the air intake on the bottom of the plane. Their UVs are pretty smashed up.
    
    
    
    
11. Lets use the Unfold tool to create less of a mash-up. Select the Unfold tool, and use the slider that pops up when uvs are selected to relax our the UVs. Here is a video of how the tool works:
    
    
    
12. If the tool doesn't work properly, your UVs might be flipped. We can enable the Colorize shells feature to see this. If a shell is flipped, simply select all the UVs and choose the Flip command:
    
    
    
    
13. Now we can Unfold:
    
    
    
14. The faces in the tail fin aren't really ready to be painted on yet. Since we are looking down on them and not at them from the side, our texture projection won't look right. We are going to have to remap these individually:
    
    
    
    
    
15. Project from the X-axis:
    
    
    
16. The Fin is purple because we mapped straight through both sides. Lets select the center edges and cut the UVs so that we can move them out for Unique texture application:
    
    
    
    
    
    
    
17. We're going to also have to create a unique unwrap for the inside of this air-intake on the bottom of the plane:
    
    
    
    
    
    
18. Now that everything is layed out, I can pack it into the 0-1 space. Problem is... When I pack this airplane, there is a lot of wasted texture space. This is parts of the map that will have to load into memory but won't be used. Its like buying extra groceries that you know you won't eat and will have to throw out. We need to optimize this layout for maximum efficiency. To do that, I'm going to cut off the wings.
    
    
    
    
19. I double click to select these edgeloops that wrap around the wings, and again, cut my UV edges.
    
    
    
    
20. Now when I rotate my shells and re-pack, things are looking much cleaner with much less wasted space.
    
    
    
    
21. Still need to UV the propeller though. So I select the nose cone (blades are parented to it, but won't map right away).....
    
    
    
22. And I create a planar map from the Z-axis (straight ahead, looking back)
    
    
    
    
23. After I unfold it:
    
    
    
    
24. I treat the first blade the same way:
    
    its ok that the shells are purple and overlapping here, since they will be symetrical from front to back. If you plan on creating an normal map here however, you cannot have this type of overlap.
    
    
    
25. But why UV each blade individually... that will take up time and waste space. Instead, lets transfer the UVs from one blade to the other:
    
    
    
    
26. Now we need to Delete our History so that Maya forgets we did all this mapping and transferring, making our scene more managable.
    
    
    
27. Lets take a look at the shells right now:
    
    
    ....and move them into place, fitting nice and snug.
    
    
    
    
28. Lastly, lets take a UV snapshot so that we can have a guide to paint ontop of (or under):
    
    
    
    
    
    And with that, the UVing step is done. We can now load this map into Photoshop and paint right ontop of it to create a texture!!!!