Transparency and Alpha Channels: The Definitive Guide

just 2 more and last questions please .
1) this method was only to prevent the white halo , right ?
2) is photoshop anough for creating clothes in SL or there is a need for others softwares as 3D stodio max ...?

thanks

Yes and no. Each tutorial includes a distinct de-haloing step. Whatever method you use (and there are hundreds besides just the few I outlined), you'll end up with a halo if you don't take active steps to prevent it.


It depends on your definition of "need". Strictly speaking, Photoshop is more than adequate for the task of making clothing (or any other texture). If you want to add other applications into the mix though, you certainly can. 3D modeling programs like Max and Maya can be used for previewing your textures on the avatar mannequin model before upload to SL, and for baking lighting and other effects onto the textures.

For the previewing, the Second Life Clothing Previewer is a simple, free application, which works quite well, so you don't need to buy a full 3D modeling program just for that (but you certainly can if you want to). You can find a link to dowload SLCP in the stickies at the top of the forum. Or, if you upgrade your Photoshop to CS3 Extended, you can preview your textures on the model right inside Photoshop itself.

As far as the lighting and other effects, you could do all the same things in Photoshop alone if you're good with it, so again, you don't NEED to bring in a 3D modeling program if you don't want to, but you certainly can if you do want to. Some people prefer to bake textures, some prefer to paint, some do a bit of both. Do whatever you feel most comfortable with.

thank you

Okies this tutorial was very helpful but I still have a problem.

I will try to be very descriptive.

Say I have a 512 x 512 image.

I want only one small area of the image to appear glasslike. Not completely transparent, but like a level of transparency. How do I do this? I am going nuts. I know how to make an entire image look glasslike. But, can not figure out how to do just a portion.

I am using PSP 8

thanks for any help.

If you want part of your image to be translucent, paint that part of the alpha channel gray. The darker the gray, the more transparent it will be; the lighter, the more opaque.

To understand the process, try this:

1. Open any existing image on your hard drive, or make a new image. Any picture will do, a photo of your Aunt Bee, a polar bear blowing his nose in a snowstorm, a smiley face, whatever.


2. Give the image an alpha channel that has nothing on it but a large gray circle in the middle of an otherwise white canvas.


3. Upload the image to SL. You'll see you've now got a large translucent spot in the middle where the gray circle was.

Get it?

Okay am going to try this right now thank you

Okay, I'm doing something wrong

when I do this, the portion of the image that I wanted to be "glasslike" becomes completely transparent. argh


nevermind I figured it out. I had to use an overlay not a solid color for the part on the image I wanted to be glasslike. Thanks for the help.

I'm not sure what you mean by "overlay" or "not solid color" in this context. By definition, anything on that alpha that's black will be transparent, anything white will be opaque, and anything gray will be in between. In my mind, black, white, and gray are all "solid colors". What do you mean?

Im using photoshop elements and the instructions here work well for an opaque alpha texture eg the bikini but how do i make a texture semi transparent with elements. I want to make a graduated texture from white at one end to 100 % transparent at the other. Ive been struggling with it for months and still have had no success, probably partly due to the fact that theres barely any tuts etc for alpha channels with elements. Thanks.

Shep, it's been a while since I've used Elements, but I think this will probably work. Let me know if it doesn't.

1. Create a new image with an all white canvas.

2. Create a new layer, and flood it with a foreground-to-transparent gradient. I believe PSE has a preset for this you can select from the thumbnail palette in the gradient tool's options box. If there's a little transparency checkbox anywhere in the gradient options, make sure it's turned on.

3. Ctrl-click to select the gradient layer, and then go Select -> Save Selection. This should copy the gradient to an alpha channel.

4. Turn off visibility on the gradient layer so that all you see is the white layer, and save as 32-bit TGA.

If PSE works the way I seem to remember it does, you should now have a white texture that is opaque at one end, and grades to full transparency at the other end.

Thankyou Chosen Few, it worked at last I knew there was a way.

Glad to hear it worked, Shep. I wasn't able to test it myself.

Hey does anyone have that old file format that was on the forums that allowed you to save things with transparent background without this caveman method? Everyone says that file format was corrupt, archaic, and left behind white halos.. But for me it was opposite, it worked great, was much less tedious than this method, and the only method that didnt leave behind halos. I used it on PS7, CS, CS2, AND CS3.. But forgot to carry over the file format document when I reformatted my computer. Anyone got it? Thanks.

PLEASE DO NOT SPEAK OF THAT IN THIS THREAD!!!

I will not have this guide corrupted by the suggestion that that dismal failure of an experimental TGA hack you're asking about could ever in any way be a good idea. There's an entire section in the FAQ at the beginning about why you should not use it. To summarize quickly again, the files it creates are:

* extremely prone to sudden irreversible corruption
* incompatible with 99.99% of all graphics applications
* visually inferior to images made with real alpha channels
* often considerably more time-consuming to make than images made with real alphas

Making a proper alpha channel, on the other hand, is a 2-second process, and it always works. There are extremely good reasons why alpha mapping has been a graphics standard for decades. Don't sell yourself (or anyone else) short by any further talk of that automated piece of garbage.

Instead of insulting the entire graphics industry by calling one its most basic tenets "a caveman method", how about proving that you yourself are indeed smarter than a caveman by learning to do such a simple thing. Read the instructions. If there's something you don't understand, then by all means, ask. Trust me; once you get it, you'll kick yourself for ever having thought it was in any way difficult.

If you really, really, really are allergic to the learning process though, and you really, really, really can't stand any other method than what-you-see-is-what-you-get, then use PNG instead of TGA. PNG can use simple transparency.

Besides, Ravenis, you don't need it any more.

If you don't want to use an Alpha Channel, and have all that extra flexibility, power and control, you don't have to.

Just save as .png, not .tga, and you'll get what you're after.

Hope this helps!

Hi does someone have a link to building techniques in SL that can avoid the alpha sorting problem? Thanks very much vor any help ....

The only way to "avoid" it is to build around it. There's no way to stop it since it's an OpenGL thing, not just an SL thing.

If you ask professional game artists how they deal with alpha sorting, the most common answer you'll hear is "we avoid it at all costs". In other words, just don't put multiple alpha'ed surfaces near each other. Make sure there's always something 24-bit in between to block the effect.

I realize that's not exactly a detailed guide or anything, just a general tip. Maybe putting a more fleshed out guide on the building forum would be a good idea. In the mean time, apply the tip as universally as you can.

Windows and glass table tops annoy me the most in this respect. I love to shadow cast everything I create...and when I have to shadow a table with glass parts...it gets on my nerves. But, all that said, it's not too hard to build around it.

Yeah, for stuff like glass tables with shadows, it can be annoying. Generally though, I find that as long as the table is of reasonable height, and the legs are 24-bit, it works out ok. Low-standing coffee tables can be tough, but things like kitchen tables are usually alright.

I am stuck on this and it is probably something easy that I missed in reading these forums and I just can't seem to get in my head how to do

I have my lace alpha and i have my bra alpha. Can the two be put together so the bra shows the lace pattern on it? Or do I have to draw the bra pattern on the lace alpha?

Basically, I guess I am asking if two alpha channels can be merged together and if so how do you do it because for the life of me I can't figure it out if it can be done.

There are many ways to do this. Here are a couple.

If you're using Photoshop, assuming the lace pattern covers the canvas, do the following:

1. Put both channels in the same image.

2. Ctrl-click the bra channel's thumbnail to select its shape.

3. Invert the selection (Select -> Inverse or ctrl-shift-I)

4. Go to the lace channel and press the delete key. You should now see the lace pattern covering the bra shape, and everything else should be black. Turn off the selection (Select -> Deselect or Ctrl-D).

5. Delete the bra channel.


This one will work in concept for either Photoshop or PSP. The exact instructions might be a little different for PSP, but it should be close enough that you can figure it out.

1. Copy the lace alpha channel to a layer.

2. Give the layer a mask.

3. Copy the bra alpha and paste it onto to the mask. You should now see your lace pattern in the shape of the bra, and everything else should disappear.

4. Merge the mask with the layer to make its effects permanent.

5. Put a black layer immdediately below lace bra layer and then merge the two.

6. You should now see what looks like a proper alpha for your lace bra. All that remains is to copy it from the layer to an alpha channel, and then delete (or just turn off) the layer.


There are lots of other ways to go bsides just these two. Whatever you do, just remember to make sure you don't actually have two alpha channels in your image. If you do, you won't see any transparency in SL. For transparency to work properly, you need exactly 4 channels in the image, no more, no less.

Hi... I do want to make some clothes here in SL but I'm not that very adept in using Photoshop. I just bought an Alpha Textures pack and it has tons of great clothing designs. Now, it says I have to open it with a clothing template (they suggest using Robin Sojourner's template and I already got that) but this is the part where I'm stuck...

How can I apply the pre-made alpha texture to the clothing template? And how can I also apply my textures on it? I'm using Photoshop CS2. Your help with my noobish question would be higly appreciated. Thank you very much.

Ginger, your question is not about the making of alpha channels in any way, shape, or form. In the future, please keep questions on topic. Far too many people use this thread as a reference to let it get derailed. Thanks.

That having been said, since you asked here, I'll answer here. There are several ways to put one image on top of another in Photoshop. I'll cover three of them:

1. Open both images at the same time and put them next to each other on-screen. Drag layers from one to the other. If you hold shift while dragging, the new layers in the destination document will automatically end up centered. If you want to copy all the layers at once from one to another, you can shift-click them in the layers palette to select them all, and then drag the whole stack. If you want to drag an alpha channel over in the same way, you can.

-OR-

2. Open both images at the same time. Copy and paste layers from one to another using edit functions. (Select -> All, Edit -> Copy, Edit -> Paste) You can do the same with channels.

-OR-

3. Use the File -> Place command to place one image file inside the other. Open the template file, then go File -> Place, select the clothing file, and click OK. The clothing image will appear in the template document, layers, channels, and all.


None of the above has anything directly to do with alpha channels. The process will work the same way no matter how many channels each image contains. Just make sure that when it comes time for TGA output, your working document has only 3 color channels and only one alpha channel. If you've got more than 4 channels in total, the TGA won't save properly.

If you've got more questions on basic use of Photoshop, please start a new thread. Again, I'll ask that we keep this thread on the topic of alpha channels, and only alpha channels.

Thank you Chosen and apologies if I've asked this question here. I already start a new thread about this and people can't seem to answer my question definitively. They point me out to read this sticky and sadly, I didn't find my answer so I just decided to ask my question here and have it answered by the master itself. Again, thank you very much for the time in answering my question. More power! ^_^

OK, I have read through a large chunk of the 15 pages of replies since the original post and couldn't find a direct answer to my question. What differences, if any, are there between 32-bit TGAs with alpha channel masking and PNGs with transparency? Can you safely use transparent PNGs without having to go through the alpha-channel dance or are there hidden quality or other issues that I'm missing? I ask this because the graphic support in SL has obviously changed since the original post was made, as the OP comments about JPG, BMP and TGA being the only formats SL will allow to be uploaded, and PNGs are currently supported.