[3ds Max] Is there a limit to how many times you can offset UV-islands?

Dubious_Fellow

Hi, I'm trying to save map space by offsetting but I'm a little confused...

I have a bunch of walls that I want to share the same UV-space:

Here they are on the UV-sheet, stacked on top of each other with one section selected:

1. I change the selected piece's offset to 1. Can I then select the next piece and move it to 2? (I have eight different sections so can I move the last overlapping one to U: 7.0?) ...is there a limit?

2. Will so many offsets affect in-game performance at all?

3. I'm using a multi/sub with 5 IDs. Can each Mat ID have offsets?

Thanks in advance...

monster

1. There is probably no limit, but why not just leave them stacked? If you need to adjust them later they'll be easier to select. UV data tend to get optimized, compressed, or the numbers get rounded, so the further it's offset the more inaccurate it can appear.

2. No, but the appearance may suffer if compressed. If you export an OBJ with number of precision set to 2 or 3 you can simulate the artifacting.

3. Yes, but Material IDs are an organizational tool in 3ds Max, are not exported, and have no bearing on UV offsets.

Dubious_Fellow

monster said:

1. There is probably no limit, but why not just leave them stacked?

Thanks for the heads-up. I thought you had to move them to stop there being baking errors? -the sections are all different lengths.

-and how can you bake realistic AO when they are all stacked?

poopipe

You might have issues if exporting to a game engine. 

I've seen significant issues with uv precision/ interpolation on PS4 with large offsets and once even within the -1 to 1 range on a circular object ( lots of thin tris fanned out from the centre) - it's a floating point precision issue so the smaller the possible range of numbers involved the less imprecise it'll get. 

It will be engine dependent but its worth knowing there's a possibility of weird shit happening 

Dubious_Fellow

poopipe said:

It will be engine dependent but its worth knowing there's a possibility of weird shit happening 

Thanks. Sounds like I should just leave the (Offset) 1 space for the symmetried geo then.

I don't know if it makes a difference but its going into Unreal.

The other option is stacking, but I thought that created issues when baking normals and AO (unless the geo was exactly the same) -is that not the case?

EDIT: I won't lie, I get confused by the maths, but if it gets worse the further away it is, could I not offset them using U: 1.0, V: 1.0, W:1.0. If the logic is correct, that gives you 3 "safe" offsets to play with?

Eric Chadwick

For baking you just need to have 1 copy inside the square, and move all the overlaps 1 unit outside. They can still all be overlapped out there.

Why do you want to organize by offset?

Dubious_Fellow

Eric Chadwick said:

For baking you just need to have 1 copy inside the square, and move all the overlaps 1 unit outside. They can still all be overlapped out there.

Genius!

Why do you want to organize by offset?

You've lost me already! I'll just stick with one offset and will try and fit everything else onto that (this may possibly answer your question?).

Eric Chadwick

Ah, maybe you thought you couldn't have any overlaps. Naw, it only matters inside the 0-1 square, and only when baking.

Here's a pic and some more words
http://wiki.polycount.com/wiki/Texture_Baking#UV_Coordinates

poopipe

It's worth noting the overlap is only an issue at the time of baking ( if you use max you can take advantage of the W coordinate to determine bake priority  and avoid the problem entirely).

There's usually no problem just ramming everything back into 0-1 space at export time