Why is it bad to UV half a mesh?

[Kerro Perro]

I have done this a couple of times: model half an object, uv unfold it, texture it and then symmetrize. In my head i just gained double resolution on my texture if you see what i mean? And if the object is symmetrical no worries right?

But i do remember reading and hearing a bunch of times that you shouldn't do this. Now seeing as it has not yet caused any problems for me and i'm thinking of doing it for a whole bunch of object for my short i would really like to know what the dangers can be of doing this?

[Mathaeus]

I don't see any problem. BTW since XSI 4 I had habit to do the same on enveloped mesh. For example, tweak one side, delete opposite side, symmetrize polygons, re-create symmetry map, mirror envelope weights.
There are drawbacks, you can't properly bake on overlapped UV, you'll want to freeze automatic UV operators before symmetrizing, but these are drawbacks for specific cases, not any 'no no'. In my opinion.

[SamHowell]

If it looks right then it is right.

I can't think of any glaring problems but do you have the same texture flopped and repeated on the opposte side of each object? Or is it one overall texture that is covered by a two repated UV halves?

Anyhoo, seems like a good way to fill up your scene with small and secondary symmetrical objects but I would want the satisfaction (and security) of knowing hero objects have been done "properly" and have slight variation.

[Kerro Perro]

It's the first one: the texture is flipped (or flopped if you will ) on the other side.

Indeed for things like a face i would never use this but for stuff like small mechanical parts it's very handy.

[Kerro Perro]

Whoops i just noticed Matheuss' reply, thanks for the info!
Yes i think i will use this, was just wondering if it could cause any crazy errors in MR but thinking about if you can use things like planar projections wich overlap a lot this really should be ok - minus the drawbacks you mentioned of course.

Thanks to both of you!