A very large obstacle in creating 3D models for games is UV's. But what are they? The simplest way to explain it is that unwrapping a UV is like peeling the skin off a 3D model and laying it flat. In this condition, textures can be applied and wrapped back around the model, effectively applying textures to the object.
There are many ways to unwrap UV's, but this is the one that I am using at the moment. I think this will help all of you working on 3D models.
First, you need 3D Studio Max. I use version 7. Your menus may be a little different but as far as I can tell this tutorial is backwards compatible to at least version 6 and even 5 although the menu names and their exact location may be slightly different.
Import the desired model. 3DS can import a variety of filetypes, but generally when importing to 3DS I stick to .3ds or .obj
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Once imported, select the object in any pane.
You can use a selection box to highlight the whole model or if it is grouped, simply click on it.
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Next go to the Rendering menu in the toolbar and select Render to Texture or press 0 (zero key along the top of the keyboard. zero on the keypad wont work).
Render to Texture allows us to unwrap UV and export it as a texture file which you can edit anyway you like so that it can be reapplied to the model.
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Under General Settings, change the output path. Click the 3 dots to select a new output directory.
It would be a good idea to create a unique output directory for each model you work on to keep things organized.
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Make SURE you have your object selected.
If it is properly selected, it will appear in the Objects to Bake section of the Render to Texture menu.
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Next, go to Output tab in the Render to Texture menu (click on the + to expand sections). This is where we decide what type of work 3DS will be doing to our model by clicking Add and selecting the type of texture elements we want applied. Since we want the entire model unwrapped, select CompleteMap and click Add Elements.
After the output element has been added, you can select the size of the resulting texture (not shown in the above screenie, but its there). Opinions vary, but I generally go for broke and use the largest possible size for production models (1024 or 2048) but depending on your application, lower sizes are recommended. You should also name your output texture file at Name and File Name and Type, although 3DS will do it for you if you like.
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Now that you have selected your object and applied the output texture element, it is time to render. With the settings we have just setup, instead of rendering a finished model and presenting an image of it, 3DS will process the model and unwrap a UV which you can save. At the bottom of the Render to Texture menu, click Render. A menu will appear warning you that you have not specified a target map. Click continue.
Depending on what you want to do, you can tweak the settings to produce bump maps, specular maps and many other useful files.
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A progress bar may appear depending on your version of 3DS. Once it is done rendering, the finished uv map will appear on your screen! If it looks remotely similar to the one in the screenshot below, good job!
Now, simply click the floppy disk icon in the render window and save the file so that you can apply art (textures, etc) to the uv map.
I recommend saving as a .png file as it preserves the alpha layer. This helps you alot when applying textures as it lets you mask image data you dont want on the texture without having to worry about accidentally "going over the lines". Compare a jpg and png uv map in photoshop and youll see what I mean.
As you can see, uv maps are broken down into sometimes tiny pieces that may be hard to identify. It may help you to apply a color to a region so that you know where parts of the uv map lie on the model. Something as simple as making the top green, the bottom red and the sides blue and yellow would probably help you out alot while applying textures to the UV map, especially if youre doing it by hand.
This process can also be reversed to let you apply the uv map back to the model after you have worked on it. This is why we selected a different output directory, as the uv map and a copy of the model using that uv map are saved there. Any changes you make to the uv map file are applied to the model file located in that directory. The exact process for doing this varies in some versions of 3DS, but I will post a general tutorial for it soon.
Hope this helps! Goodluck modelers!
