Terrible UV unwrapping skills.
I am trying hard to improve on my unwrapping skills, but to no avail I just do not understand UV unwrapping. When do I distort things, when not to, how to separate things but have a seamless texture. I'd like to use flat textures sometimes, rather than have to custom make every texture to make it look decent. For example, on a cylindrical table (Ex1)... for the life of me I can not get rid of the pinching or distortions. No matter what I've done, this is the best I can get it to be. Or the pitcher (ex2) I can't get rid of the pinching, and the UV isn't the easiest to work with. The distortion only gets worse if I try and force it into an easier shape.
Replies
The reason you get wide and then narrow portions on your UV shells is because the model is wide and then narrow in those areas, such as the table top & base, and the middle section respectively. If you want certain areas to lay out more proportionately, you will need to separate the UV shells (cut seams) so each section has more liberty to straighten out. These are also relatively inconspicuous areas to have seams.
Generally, anything you might consider an "edge" or a "corner" (a right-angled surface) or close to it should have a UV split. There are exceptions; such as, if you are doing unlit, diffuse-only texturing, you can fudge where you place your seams a bit.
Forcing the shell's shape is sometimes necessary and helps a lot with texturing (it's way easier to paint on a rectangular UV space than one shaped like an hourglass or a bow tie ). Maya has tools to align UVs vertically or horizontally to achieve this, but the larger the distortion there is between sections of the shell, the less effective this becomes.
For your table model I would recommend cutting the UV shell at the top of the base, and the underside of the tabletop, then unfold try unfolding again. You should get better results. For your urn you might be able to get away with one huge shell that's been aligned into the shape of a rectangle. There will be some distortion but it might not be so bad. You'll have to use your judgment. If you are baking normal maps, you should split your UVs along the rim of the urn, separating the outside from the inside.
If you are using pre-existing textures (seamless or trim sheets) your UV placement relies more on how those textures look with the textures applied. In this case, you are free to do whatever you want to your UVs as long as the textures display properly. Here's an example of some props that all use the same texture maps, but with the UVs specially arranged on each one for proper display:
Example
There are some tutorials you could follow if you want to see some examples. Millenia's m37 Shotgun tutorial and Joe Harford's tracker knife series spring to mind.
Also I gave some uv advice in this thread which you might find helpful. Maybe I should make a UV tutorial at some point... I find it interesting at least and there isn't as much info on it as other things like baking.
Generallybut in some cases it may be better to add extra edges (so you don't have to split the uv's) for larger, more manageable (and easier to texture) uv islands, for only a little extra cost (since you've got less seams, therefor less hard edges/split verts, assuming you set hard edges by uv seams).