White line along the edge of my transparent panel

The project I've been working on is the creation of butterfly wings for my avatar. I'm mostly pleased with the results. Thanks to tutorials in this forum I was able to create the wings with a transparent background and paste those on two opposing sides of a cube. I then pasted a totally transparent texture on the remaining 4 faces. I then flattened the cube down to a flat panel.

Most of the time this looks pretty good, but occasionally I can see a fine white line along the edge of the panel.

Does anybody know how to get rid of this?

(If you need more details, I have screen shots and step by step description of what I did on my blog secondlifehowto.com)

See the sticky Transparency & Alpha thread:

/109/32/80851/1.html

Especially the section marked "Why do I see a white halo around my partially transparent images in SL?"

-peekay

Hi Clayton. I have a couple suggestions and comments for you.

Before I get the the alpha channel stuff, I should probably mention you might want to change the Snapshot_0011.bmp image on your website to a JPEG instead of a BMP. BMP's are uncompressed, and take a really long time to transfer over the web. You might see it quickly on your end since because it's your own image, and you made the page, you probably already have it cached, but it took a good 15 seconds or so to load for me, even though I'm on a 30Mbps cable. Anyone on DSL would likely have to wait at least a minute or two, and if someone's on - god forbid - dialup, it'll take all day. It's a 2MB image file right now. As a JPEG, it would probably be like 100K.

Also, I'd suggest changing the file name to all lowercase letters. Some browsers have problems with uppercase.

Your tutorial looks great, but I'd recommend changing just a couple things. First, I'd caution against openly recommending people grab images from Google. If you're going to suggest that people use pre-existing images instead of making their own, then it would be a good idea to mention that they should be sure to search for images that have open copyright. To use copyrighted images without permission is illegal, and EVERYTHING is copyrighted unless it explicitly says otherwise.

Second, I notice you did not include a de-haloing step. If you take a look at your snapshot, it's easy to see why skipping that step is not a good idea. Notice the white outlining (halo) surrounding the butterfly wing? The edges of the actual wing are dark blue or black, and should be nice and crisp, but since you didn't de-halo, your wing has a ghostly white blur surrounding it.

To get rid of the halo, simply give the image a dark background. When you go against a transparent background (mathematically equivalent to white), you get white pixels around the edges due to anti-aliasing on the alpha channel. You want a background color that is similar to the real edging of your image subject, so that those anti-aliased pixels will blend instead of stand out. In this case, dark blue or black would be ideal.

As for the white line on the edge, there are a few possible causes. Most commonly it's due to the fact that SL doesn't clamp textures. It tries to tile everything, and as a result, you often can see the edge of an image "bleeding" over to the opposite edge. Setting the repeats per face to less that one usually solves the problem. Try setting it to like .95 or so, and see if it gets rid of the line.

The other possibility is you may have a thin line of white on your alpha channel. You might want to go around the edges of the canvas with a good size paintbrush to be absolutely certain every pixel is black.

Hope that helped.

Thanks that did it. A black background got rid of the halo and changing the repeats per face got rid of the line at the edge of the panel.

Thanks also for the suggestions on my blog.