When working with UV mapping it is often useful to be able to see how the UVs are unwrapping. Here are two JPEG images that should help in the arduous task of UV manipulation. If you add these to a couple of materials and then save them into your Cinema4D preset library then you will have access to them whenever you need.
There are two images, one is a simple grey checker with markings showing the four corners of the UV space. The other is a little more complex and the UV space is broken down into even segments defining the coordinates of the UV space, it also has a four colour gradient mapped across.
The grid itself is useful as it allows you to see how much distortion you’re introducing as you pull the UV points and polygons around. You can always tile the material to repeat the grid across the mesh.
The more elaborate coloured version will show you a smaller grid without tiling the material. The addition of a gradient will show you where you may for instance, have flipped a UV polygon back to front, as the gradient will not flow smoothly over those parts of the mesh. It is useful for determining how continuous your UV mesh is and the numbering of the sections will tell you where in the UV space any problems occur. This makes it easy to look at a complex mesh and if you locate a UV mapping problem on the object, you can then use the UV coordinate from the image to help you find the offending point or polygon on your UV map quickly.