Rectangular size texture map

Usually we will create square size texture map and for games engine, it'll mostly must be power of 2, e.g : 512x512,1024x1024,2048x2048. However there are particular case which require rectangular size, like 1024x512, or 512x128.

In maya itself, the uv range is always square, this is confusing because if we have a rectangular size texture slapped on square size layout, it will be stretched. Look at the image below.



The uv size range from 0 to 1. And it's square. Let's apply rectangular size texture.



The texture is now stretched. What if we want the uv to follow the texture rather than the other way round?
Use image ratio as shown in the image.



However, this result UV to stretch. Therefore, you need to work in the proper uv (image ratio on).
Once you're done with the uv, you can turn image ratio off. It'll look stretched (shrinked), but it doesn't matter, because that's the correct uv with correct texture. Unless you're planning to change the texture size :)