Multiple UV Performance?

16bit

What I have is a car skeletal mesh and I want to add decals on it like flames, stripes, etc. Now I want these decals to be used among several different cars and recreating them for each vehicle would take up a large amount of harddisk.

So what I want to do is create a new uv layout for every decal like you can do in max.

So what I'm trying to do is exactly like what this guy did with his.
http://zivcg.com/popups/shadingtut/5.html

My question is, how big or small of a performance issue would a car have with a large number of uv layouts. Or is there a limit a mesh can have in udk.

tristamus

I'm sure it would work in UDK, but then I'm pretty sure you're talking about 4 separate draw calls, and I don't know if it's worth it then. Same goes for any mesh....

However, I may be wrong about the draw calls. If somehow it all pulls from the same material, I think that'd still just be 1 draw call even though you have 4 UV layouts.

Froyok

4 different UV are alowed per mesh in udk.
It's the limit with the last b

Xoliul

You should create a default Decal UV layout, to which you try to conform all cars and all decals, that way you don't need to create a new unwrap for every decal, which sounds like a bad idea (too much work, impossible due to max 4 UV's).

16bit

Alright. So how I plan to do this now is.

The first UV is going to be the normal map which is symmetrical.
The second UV is for the diffuse, for cars that have custom paint jobs* (sponsor stickers, logos, etc)
The third UV is for decals. Such as flames on the side of the car, or strips. These will be located on a 2048^2 texture with 64 decals on them that have enough space for 256^2.

*On an unrelated note is it possible for a player to import his custom paint job to use in game? Is it possible for udk to recognize something not in a .upk file?

Vailias

Custom textures are possible, but the players may have to pack them into UPK's first, then you'd need to create a system to load that custom texture into the proper material slot.

Last I knew UDK didn't do on the fly external asset loading.

16bit

So performance wise, is this OK to have 3 uv's? Like it won't drastically slow down the game.