Texture Edge "transparency" / seam

Hi,

Apologies if the answer to this is already here but I haven't been able to spot it.

I have two textures which tile seamlessly to create an image which spans across two prims. The textures were carefully cut from one larger image to preserve the level of detail required, and I have checked and double-checked that before upload to SL they do indeed tile seamlessly ...

However, something seems to go wrong when I upload them ....

As soon as the upload is completed I can see immediately on the preview that for a single pixel width on all four sides there is a kind of semi-transparancy which seems to flicker as I move the preview around the screen - this is reflected when I actually apply the textures to the prims in-world as an obvious seam line between the two textures.

I know that this is not just something I should have to put up with because I have many textures created by others which do not have this strange property, so I was wondering if someone could tell me what I am doing wrong.

I have tried saving the files as 24 bit TGA, 16 bit TGA, and have tried at 1024x1024, 512x512 and 256x256 (I really need the resolution of 1024x1024 for these anyway ...) but always get the same results ....

Can anyone suggest where I am going wrong.

Thanks

The only thing that comes directly to mind is that there is a small amount of feathering used when making the selection to copy.
That would leave a very slight transparency around the edges of the image and if flattened, would (usually) take on the background colour.

Other than that, I assume you are using PS (I use Gimp) and may be something specific to that.

I've seen something similar to this when using textures which fade to transparent at the top - a repeat of 1 per face repeats the first line of pixels from the bottom of the image so you get a seam along the top of the transparent bit.

Try using repeats of slightly less than 1 to get rid of the edge pixels. Or, if you can bear to lower the resolution, you could put the images side by side and upload as 1024x512, then offset on each prim 'til they line up.

Thanks for the suggestions - I really cannot figure out why this is happening ... I have tried creating the textures in PS, GIMP and PSP and they all look fine in all of those programs, there is no alpha channel, and to be certain I even tried saving them as bmp's but the seam still appears when SL does its conversion to JPG2000 .... just can't see why ....

It seems to happen with any image I upload, not just these specific ones.

I have tried repeats of slightly less than 1, but that loses the precision of the join and so the seam is still visible due to the missing coulm of pixels from the complete image ... I think I shall have to create my images at 1022x1022 and then add a 1 pixel border all around which I will then shave off by using a repeat of less than one, but that's going to be a bit of a pain

Since I seem to be getting this issue with any image i upload I just wondered if there was something crazy that I was doing wrong .....

Yeah it seems to happen on all textures, it's just sometimes more noticeable if you are using an alpha texture, or, like you, a high-res texture that has to be just so.



That's a good idea. You could also try shrinking the prims very slightly, without stretching the textures. Something that's just occurred to me ... are you sure it's a texture seam and not a prim seam you are seeing?

When I first started doing .raw files for multi-sim terraforming projects, I noticed I kept getting a strange bit of trashed pixels on the edges. This resulted in odd micro-fine ridges where two pieces should have joined perfectly seamlessly.

After investigating the issue, I found that if I sliced the image apart while it was still larger than my intended import size, or reduced the images and then imported them, I got this flashing on all edges. If I scaled it down and then cropped and saved the slices, I got the effect only on the outer edges.

What seemed to be happening was that when cropping the image, the Photoshop application was actually trying to anti-alias the edges to the non-existent pixels past the edge! So I had a tiny halo of transparency at the edge of the texture. On a non-alpha texture (24-bit TGA), this resulted in a slightly lighter seam at the texture edges. And a ridge in my seamless .raw files.

The work-around was to make the texture with a thin margin of unused image past the edge, and crop to that.

One way to "fix" a texture suffering from this micro-transparency at the edge is to take the affected image into a graphics app like Photoshop, duplicate the layer, set guides at the existing edges of the image, expand the size of the lower image by 2 or 4 pixels, merge the two layer, and then crop to the intended edges. This provides a pixel or two past the edges that should be an almost exact match for the pixels at the intended edge, and the cropping therefore has identical pixels to anti-alias the edge to.