UV mapping question

[Zaeo]

Hey there guys, I was wondering if y'all maybe had an answer to something I've been wondering...

I have been working my butt off on some models for my parts pack, and was wondering a little bit about UV mapping...

the "edges" of faces within the UV map, do the edge themselves count as a pixel? I ask this so I can utilze almost 100% of the UV space by means of resizing and the like.

For example,

Face 1 has vertex coordinates of:

0,0;0,32::32,0;32,32

Face 2, of a separate seam has vertex coordinates of:

32,32;32,64::64,32;64,64

Would I get all of the pixels on the edge, ie 0-32 and 32,32 as separate lines, or do the edges themselves count as pixels?

Am i going to have to size it down slightly smaller than a 32x texture face? Or can I, in a image manipulation program like gimp or photoshop, get a perfect 32x texture face for each, utilizing what happens to be a 1042x1024 sprite map?

Thanks!

[stubbles]

The edge is simply the edge of the island. It's "width" is nonexistant, it's simply the end of the island.

One thing you want to keep in mind though, is mipping. You need edge padding and space between each UV island, in order to prevent mip bleeding. The amount of padding needed goes up with texture size. Some more info for ya: http://wiki.polycount.com/EdgePadding?action=show&redirect=Edge+Padding

[Zaeo]

Does mip bleeding still occur on 90 degree angle faces? I'm designing my models in such a way that is is almost entirely 4 point 32x64 or 64x128 textures for the most detailed faces.

aka, if i had no circles, I could use 100% of the 1024x1024 texture sprite.

[stubbles]

mipping is just the natural downsizing of textures at distance so yes, mip bleeding would still occur. Even if you use 100% of the space, if it's for an unwrapped model and not used as BSP style texture, you will get some kind of bleed. You just need to plan for it.

[Zaeo]

Okay, thanks for the help

From what I understand a 1024x would be okay with a 4 pixel padding but ideally you want 8 pixels?

that leaves...wow, that essentially means you loose about 10-15% of usable texture space O.o

Final question: In the "mipped texture padding" that you leave, is it better to put it as a solid color, or leave it transparent? I work with transparencies in a XML multi-layer image for editing, then export to PNG. The transparent square indicators is how i determine different faces from other sections...do I extend the texture out 4 pixels in all directions from that face*If i were to use a 4 pixel padding* or leave it a solid color, or even transparent as i have been doing it.

I can say this, I did notice quite a bit of "mip bleed" on a few of my models, now that I know the cause, I can fix it.