edge glitch on .tga files?

I ran into something strange recently. I think it's a rendering glitch, since some wings that I made earlier and which looked fine a few releases ago are now showing this bug.

I have a pair of wings which are a single, flat prim per wing. The entire prim is textured to a 100% alpha texture to start with. Then the flat front and back are selected individually, and a wing texture is applied, which has alpha-mapped transparency where the wing itself is not there.

What is happening is that on the 'left edge' of the wing, the edge that would be to the left on the original texture, I'm getting a one-pixel line of scattered dark pixels. The dark area does not match up with the coloring on the far edge, where the wing texture flows right to the edge.

I checked and re-checked the master for the .tga texture, and the alpha mask is solid black all the way to that edge, and there are no pixels at all on the wing's texture layer at that edge.

If I set the horizontal repeat for that face to 0.99, the glitch goes away. So it's not some texture showing on the thin edges, which are still 100% alpha. It's how it's rendering the flat face.

Why???

Wow, I noticed the exact same thing yesterday on a sign that I have. Actually, the sign is does not even have an alpha channel, but it is a TGA file. It is applied to the front of a box, and on the left edge is a line of pixels. All other edges are fine.

There is a one pixel "wrap around" from left to right and top to bottom. This is considered a Good Thing for reasons I don't get. The fix is easy: set repeats per face to 0.98: gone.

Thanks to Mr. K. Fate of Peoria for this tip.

It's there so that when you don't get a seam between two prims with a repeating texture, I'll spare you the technical details as to why.

aye, you can set the repeates or the offset just a shade to fix it.
but to me the little line seems to be abit more obious since 1.8, but maby thats just me

Yes, setting repeats to 0.99 fixes it, but that glitch wasn't there a few releases back. Those wings looked fine then, even when I was standing against a white wall.

The seams in textures were first noticed in 1.7 and has probably to do with the JPEG2000 compression compressing your textures and leaving an unsightly border. I'm not sure if they recompressed everyones old files in the asset database, but admitting this might create an uproar from everyone, so best LL keeps quiet about it.

It is more noticeable if the texture that was uploaded wasn't in power of 2 dimensions, like 256, 512, 1024, etc. because it gets restretched when being uploaded.

Scaling it to 0.98 or so isn't the best solution if you're trying to join things like long or large paintings and photos together, because it still creates a mismatched edge.

I've managed to piece 4 textures seamlessly together tho, by scaling a 1024 x 1024 pic down to 768 x 768, but placing it on a 1024 canvas. When in SL, I just scale it to 0.75 and match the corners.

IM me if anyone wants to take a look at it. I'm sure nobody would bother tho.