The Basics of Modeling and Texturing

for Rise of Nations

Part 2) Unwrapping

Unwrapping the model to make it easy to texture is important. What the unwrapping process does is to create a texture template for you to create a skin using photoshop or similar tool. It also associates each vertex in your 3D model with an (X,Y,Z coordinate) to a 2D coordinate (U,V coordinate with values from 0 to 1.0) on to your texture template. The 3D model then in effect has been flattened out onto a 2D surface. Imagine if you will if you took a cardboard box, cut apart all the sides and the layed them out on the floor to be painted. Except that the .3DS file records where in 3D space each corners of the box you just layed out should be and where on the floor those corners are. This lets you reconstruct the box from its faces and what color you may have associated with the faces when you painted them on a flat surface. We will go through step by step how this is done using LithUnwrap. But again we will not going to go into great detail in how to use LithUnwrap, but what we will show you is the basics and how to make the most out it.

1. Take the .3DS file you exported from 3D Studio Max and Open the Model in LithUnwrap. You should see a small box on the top left corner of the workspace window. This is the model in its UV form.
   
2. Select the small square in the corner. Make sure you group select it (drag select) especially if you've named the parts as recommended in the previous tutorial. Once selected we can proceed to map the 3D model onto a UV map.
   

   Go to Tools > UV Mapping > Box.
   

   Choose side by side and scale to mapping space options. The picture below shows how this should look like.
   

   
   

   This will give the model a UV map which we can move around and make a texture template. We are far from done but, you can save the model now with a UV map associated with it, as UV_Tiger.3DS
   

3. Now the UV map should look like this.
   
   

   Notice how the tank is now made up of a bunch of triangles even though originally in your model they may have been made up of a variety of shapes. You will notice also that the faces tend to overlap now that they model is formed by triangular faces with the tank viewed from each side of a box.
   

4. Separate up all the different parts, e.g. Hull, Turret, Main Gun, Tracks etc. This will take time, so be patient especially if you didnt name the parts, since it is easy to loose track of what face belong with what. If you had named your parts then this process should be a little easier, and you can isolate the parts by selecting them on the grouping tree on the right side.
   
   

   You should generally be in the select faces mode during this process. You can hold shift to select more faces and Ctrl will de-select them. Drag select will also work for groups of faces.
   

5. After separating the parts, the UV map should look something like this. You may need to use the group->unhide->select all->apply tool to display all the parts of the model after moving the parts around.
   
   

   But this is still of little use for texturing. Much of the UV map space is un-used, and there are many redundant faces. If you just used this texture template, you will not be optimizing the space you're given, and reduce the level of detail you can add to your texture, and increase the amount of work in painting unnecesary surface areas.
   

6. We should try to first get rid of all the redundant elements. Such as the left and right wheels should be the same, as well as parts of the hull and turret. The two sides will generally look the same ingame so they might as well be overlayed on top of one another. You can of course choose to distinguish the sides and not merge some of the parts with their opposite sides if you really must make them different. But for those parts that you wish to merge, use need to flip them and move them around in the the UV map.
   

   Edit > Flip > Horizontal
   

   Then move it over on top of the other side until it looks all red. After merging the redundant parts, the UV map should look something like this.
   

   
   
7. Arrange the parts so they line up on the UV map. This will make life easier if we want to put a pattern over the model that stretches into different parts of the tank such as camouflage. Move each section so that they physically align to the part that they should connect to on the 3D Model as best as you can. Now do this to all the other parts till you have each part in a box like shape then we can arrange them so we don't waste space on the texture. To make this process easier, you can use the Vertex mode to change the shape of the object by moving the corners to meet each other as they would if they were in 3D. One word of warning about this. It will distort the shape on the 2D texture map (although this will have no effect on the 3D model itself). If the texture you want to make has little detail but mostly camouflage patterns this will not be a problem. However, if you like to add decals or detailing, I would suggest you leave the vertices alone and paint camouflage pattern near the junctions using a little trial and error, since it will be much harder to draw a decal that needs to be skewed or distorted intentionally.
   
8. After arranging the parts as best as you can. It is best be maximize the space used so that maximum detail can be put into the texture. You can't afford to waste any on a 256x256 texture map. I suggest you put all the smaller details to one side and position the main parts first, then fill the gaps with the details. Select the parts you want to resize, press the "s" key, this will make a green box appear over your selection. Move the green corner vertices to resize as you wish. Your attempt to arrange the UV map will probably be different then the example but it should look something like the following picture when you are done.
   
   
9. Now click on the little disc and save the finish UV mapped Model (File->Model->Save).
   
10. Finally, save the UV Map as a .TGA file in Black and white mode with width and height 256 (File->UV Map->Save). Select "Color & Outline" and "Fill" is checked. It should look something like the picture shown below. You can choose "Black & White" mode as well, but I find that the color is a good way to start the template with a base coat of color. You can always fill it back in with another color later. Also the "Outline" option, or the Unfilled option in Black & White mode, that creates the lines within the template can be later used as a guide for painting in edges on the texture skin.
    
    

    You are now ready to paint the texture template.

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By One_Dead_Angel and Unit35