Tread Marks Tutorial
For this tutorial, you will need: 1. A 3D modeler. A program you can use is MilkShape3D. 2. A graphics program. You can use Adobe Photoshop or Paint Shop Pro. 3. A 3D model. I'll be using a Tron tank model for this tutorial. You can download it at 3dcafe.com in the Sci-Fi section.
This tutorial explains how to model, map, and texture a tank for the game Tread Marks. It is divided into 3 sections: 1. Modeling 2. UV Mapping 3. Texturing
Modeling
1. Import your tank model into MilkShape3D:

Click Tools->Print Model Statistics and look at the model's dimensions. It's too big, so we have to scale it down. 2. Use the modeling tools to scale, rotate, and center your model appropriately.

The tank is now scaled, rotated, and centered appropriately. MilkShape3D uses a right-handed coordinate system, so the magenta represents z+, yellow represents x+, and cyan represents y+. Our tank is facing in the z+ direction, so it is aligned correctly.
3. We need to separate the tank body from the barrel and turret, so save the same model to two different files. Then delete the parts that are not needed in each file.

4. We need to align the turret to the origin, because this is the point where it will rotate in the game. Then align the tank body to the turret, so it looks good. If you save both parts to a LWO file, you can merge them together temporarily by importing one part into the other file to see where they line up.
5. Lastly, export both parts to separate LWO files. I named them tank_body.lwo and tank_turret.lwo. A word of caution: MilkShape3D might invert your faces, so they might look all black. You can fix this by clicking Face->Reverse Vertex Order to flip them back if this happens.
That's it for the model. Now let's move on to the UV mapping...
UV Mapping |
1. Load the tank body into LithUnwrap. It has no texture coordinates, so the program applies a box mapping to the model by default. Tanks are generally box-shaped, so this is what we want. However, the groups are overlapped and it will take a little longer to separate them by hand. So, apply another box mapping, but this time, check the "Separate by groups" option:

2. To free up some space for the turret, we can mirror all parts that are identical. Mirroring means will will use the same UV coordinates for opposite sides of a part. We can do this by flipping a part vertically or horizontally and moving it onto the other identical part:

We are done with it, so save the model to tank_body.luv, and save the template bitmap to tank_body.bmp. 3. Load the tank turret into LithUnwrap. It has no texture coordinates, so the program applies a box mapping to the model by default. Again, apply another box mapping and check the "Separate by groups" option:

4. Do the same thing as we did with the tank body, mirror the identical parts. Then scale them so everything fits neatly on the left side:

We are done with it, so save the model to tank_turret.luv, and save the template bitmap to tank_turret.bmp. That's it for the mapping. Now let's move on to the texturing... Texturing 1. We are going to use the layering tools in Adobe Photoshop. You can also use the layering tools in Paint Shop Pro.
Create a new document with two transparent layers. Then copy and paste tank_body.bmp and tank_turret.bmp into each layer:

You can begin to see how the final image is going to look like when we merge the two images together. 2. First we want to get rid of those lines. One way we can do this quickly and easily, is to use the magic wand tool. We select everything black with the magic wand tool, then inverse our selection to get the outlined parts. Then we fill it in with an arbitrary solid color. Do this for both layers:

Optional:
In addition, you can select everything black again for each layer and delete it. This will make all your layers transparent. You can then add a background layer (shown below as Layer 3) and use that as a base color for your texture:

3. Now we can texture our tank model. For example purposes, I'll just do some simple texturing:

That's it! We have our 512x512 texture with the tank body and the tank turret, and our two LUV files. Let's see what it looks like in the game:

Not too bad for a quick 5 minute texturing job. :) I textured each part a different color, so you can get a good idea of where the texture goes. It is also a good way to check to see if there are any mapping errors. There are a lot of improvements we can do from this point on, such as detailing, better texturing, better mapping, better separation of parts, optimizing the poly count in your model, etc.. but this tutorial should be enough to get you going.