Straight-Edge UV seams
polycounter lvl 14
This is one thing i've wondered for a while now. Although i've been unwrapping for years now i still dont figure how various maps like those seen in games like RE5 for instance have dead straight texture seams. I know how to straighten seams using polyboost or textools etc but why would you do this as surely its virtually never representative of the actual UV space (as seen by relaxing them - usually resulting in organic curved sides). I've always figured it was just a case of developers wanting to make it easier for texturing - having that nice clean edge - but at the expense of a little UV distortion. Maybe i've been missing out on something golden here but is there a way of unwrapping say trousers/pants with a dead straight edge either side without UV distortion?
Perhaps it's a case of relaxing / making seam planar and then locking borders when relaxing further but i'm figuring this will still lead to uv distortion (minor).
Perhaps it's a case of relaxing / making seam planar and then locking borders when relaxing further but i'm figuring this will still lead to uv distortion (minor).
Replies
Obviously the more you deviate from the mesh shape, the more distortion you'll get, but in most cases it's never that bad. It can be a lot easier to fit together UV shells if they have straight edges too, but it takes a bit more time to lay stuff out that neatly, and in most cases you don't save aaaaaaallllll that much space anyway.
the general conclusion went something like: the more next gen you go, the less perfect straight UVs tend to matter: they're great for using pixels to create straight lines (because of off-straight UVs creating the need for anti-aliased lines) but sometimes the uv distortion means although you squeezed more space out of the map, it looks worse anyway (because you're creating uneven texel ratios)
afaik there's no way you can straighten the lines without distortion, if the mesh isn't right angles (disclaimer: I'm not talking about normal maps or other bakes obviously because they have the distortion baked in to the texture)
edit: ps, I'll include a quote from per on the matter
This thread for example http://boards.polycount.net/showthread.php?t=68545&highlight=failed+art+test
http://www.disneyanimation.com/library/ptex/
http://ericchadwick.com/img/cowgirl.html
My texture was pretty low-res, so each pixel counts. I made the UV for the top of the pants totally straight, even though on the model it curves up and around her hips. This let me use a single-line shadow where the belt met the pants, made the belt loops easier/sharper, and better stitching along the crotch seam.
This technique is commonly used in large-volume projects, such as MMOs. In such projects, the game requires a very large number of prop and weapon models, as well as numerous texture maps for character clothes. With so many texture maps getting painted, it is important that they be easy for the texture painters to work with. For a one-time portfolio piece, you would have a little more leeway in laying out your UV maps.
The way Ptex is implemented in 3D-Coat it would work just fine in games or any 3D program for that matter, whether that program has Ptex support or not.
[ame]
Andrews solution isnt practical at all for games. Its splits every face of the model into a seperate UV island. pretty much doubling the vertex count of the model. Id imagine the bleed on the smaller islands would be pretty apparent also.
He did however mention somewhere about using a premade uv map for baking though.. this sort of defeats the purpose of ptex though.
as an aside. do you guys projection paint much or are you all photoshop users.
From what I've come across and read, it seems this really only works well if you're going to use a small texture map though and not necessarily big texture sheets like 1024's or above.