Transparency and Alpha Channels: The Definitive Guide

Hi,
First, I'ld like to thank Chosen & Robin for providing such fantastic tutorials.

I'm still having a bit of trouble with the white halo effect unfortunately. I remember finding the solution a few months ago on Robin's site but it's been replaced with the Flaming Pear plugin fix. I downloaded the plugin last night but unfortunately it's still creating a white halo for my image (I tried all - A, B & C). I think it's because my image has gradient edges and is also a intricate ivy design. I know the previous tutorial video (on Robin's site) is no longer available, but was wondering if you can tell me the steps for the previous white halo fix. I just remember it had to do with gaugasian blur ...bah, my memory! It worked like a charm several months ago when I was working on a tree alpha and I forgot to write down the steps. Any possible way of getting the steps? No need for a fancy video

Any help appreciated.
Thanks again in advance!

Krstopj, the Gaussian blur method and the Solidify method are basically the same thing. If one worked for you, so should the other. Both simply employ a method for bleeding the color data past the edges of the opaque parts of the image. There are a hundred ways to do that. Substituting one filter for another doesn't change the principles involved. If you're having problems now, it's not because of the Solidify filter. You must be doing something else wrong.

My guess is you've got one (or more) of the following things going on:

1. Maybe you're using Photoshop 7.0. If that's the case, you won't be able to create alpha channels properly. Upgrade to 7.0.1 immediately via the free patch from adobe.com.

2. Maybe you're not using 7.0, but you broke the version you have by installing the 7.0 TGA plugin into it. That file's been floating around for years under such tempting descriptions as "this will end your alpha channel woes", "auto-magically create alpha channels", "create perfect alpha channels in one click", etc. If you ever installed any type of automated alpha channel plugin, or any thrid party TGA saver for that matter, you'll need to uninstall Photoshop and reinstall it from scratch before it will work properly again.

3. Perhaps you painted your subject directly onto an already solid background layer instead of onto its own layer(s). While having the subject on the same layer as a solid background won't prevent you from creating an alpha channel, it will interfere with the particular method Robin outlined in the video, and with most of the methods described in this thread. For easiest work flow, keep your subject on its own layer(s), and don't use a background layer at all.



In any case, to answer your specific question, the steps are quite simple. Follow Robin's video exactly, right up until the part where she says to use the Solidify filter. Then do the following:

1. Put all the layers in the image except for the background layer into a group.

2. Copy the group.

3. Merge the copy. You now have your original layered work preserved in the first group, and a flattened composite of the whole thing, which will be the source for the blur bleed.

4. Turn off or delete the background layer, a then put that flattened composite layer we just made all the way at the bottom of the layer stack.

5. Apply a Gaussian blur to the composite layer. This will smear the colors, bleeding them a bit around the edges. But the bleed will be very faint right now.

6. Copy the composite layer a few times, and merge all the copies. This will make the bleed appear less faint.

7. Repeat steps 5 and 6 a few times until the bleed looks solid.

That's it.


The seven steps I just wrote out are a slower way of basically doing the exact same thing the Solidify filter does in just one click. It doesn't change any of the principles involved with making a proper alpha channel. All it does is bleed the colors past the edges to prevent haloing. You could do the same thing with the paint brush if you were patient enough. Solidify is by far the fastest way to go, but anything that has the effect of applying similar colors around the edges of the image subject will work. Use whatever method makes you happy. The alpha will come out the same either way.

As I said, there must be something else going on if you're still getting a halo with Solidify. It's probably one of the three things I mentioned in the beginning, but it could also be that you're doing things out of order, or just plain doing something wrong. Make sure you've got a functional version of Photoshop, read through the tutorials again, and hopefully you'll solve the problem.

I somewhat get the feeling that I'm doing something thats waay over my head.. but I'm determined and ready to try!!

I'm trying to make a skirt from a drawn picture, which makes it an odd shape, there is a front view and a side view, under the skirt is semi trandparent silk ruffles...
Now what I'm doing is cutting the picture of the skirt out, (masking tool) off the character its drawn on, and createing a new picture with it as the second layer (I'm useing adobe photoshop CS2) now I think I get the idea about transparencies via alpha channel, but I'm curious about if it will work, as it's a 2d picture of just the front and back, not the side's (will this effect it's look in the end? or will it just even out once put on a 3d circular skirt like object?)
Also, for the visable ruffles underneath it (the skirt is open in the front) should I make this another layer, and skirt all together to layer it? Or can I simply leave it on the main skirt? (how do I make it somewhat transparent instead of fully?)
AND last but not least... seeing as the front of the skirt looks completely diffrent from the back, should I somehow join the skirt side by side, like lay them out and connect them via photoshop, the upload on SL? Or how should I go about this?

((For a better idea of what I mean here is a picture of the skirt in question, that I'am trying to build.))





Thankyou for anyone and there help in this matter!

Nara Tairov~

Nara, please post your question in a new thread. It does not belong in this one.

This thread's sole purpose is to teach people to understand the principles behind alpha channels, and how to make them. While any number of the countless possible methods of creating the skirt you're asking about could involve the use of alpha channels, your question doesn't really have anything to do with the mechanics of alpha channels themselves. Therefore, your post is entirely out of context for this thread.

Please respect the importance of keeping posts on topic within a thread, especially stickied threads. Post your question elsewhere, and I'm sure you'll get lots of answers about how to do what you're asking.

For what it's worth, if it were me, I wouldn't use actual clothing at all for this. I'd use a sculpty to shape the outer part of the skirt. Then I'd use a collection of flexible cut cylinders to make the frilly part underneath. If you have further questions on how to do that, ask in the building forum. As I said, it's important not to let this thread get derailed.

Thanks.


EDIT: I just noticed you already started a new thread with this same question, about 10 minutes after you posted here. I'm assuming then that your post here was a mistake. In the future, if you mistakenly post in the wrong thread, please go back and delete the erroneous post immediately afterwards.

Besides taking into account all of your layer transparency and masks when generating an Alpha Channel, GIMP also creates an alpha channel when you have more than one layer or if you have one layer that is not a background layer (basically normal layers can contain transparency so an alpha channel is created).

To remove this from images with no transparency you have to go to the Image Menu > Flatten Image to flatten your image first so GIMP will automatically discard the alpha channel before you save it for Second Life. This way you don't have an unnecessary Alpha channel causing you any problems as you now only have a background layer.

Note: If your image has transparency any transparency will become white.

Will there never be a solution to the annoying clipping of transparant textures ? The excuse "all 3D apps have the same problem" is nonsense. I've worked with dozens of editors ranging from the Quake engine to Unreal to Source to Doom 3 etc. and each one of the engines supported texture transparancy without these kinds of clipping problems. The only problem i've seen was when two transparant textures intersected and one part was shown behind and another part in front of another transparant texture.

But the way the SL engine flips out when one transparant texture even comes NEAR another transparant texture is just silly. I can put a tree three meters away from the window but if you look at the tree with the window right behind it, it messes up! Surely this can be improved?

I'm not sure why you saw fit to post your little rant in this thread, Icarus. You don't like the way SL handles alpha sorting, got it. How exactly does that benefit anyone trying to learn to create alpha channels? If you've got a question on how to make them yourself, or if you have tips for people trying to learn, by all means contribute. Otherwise, please don't waste people's time like this. This thread is for education, not for complaining.

I'm only guessing that alpha sorting is what you meant, by the way, based on your description. You kept saying "clipping", which is not the correct term for what you were describing. To "clip" in 3D terms means to define a region in 3D space in which objects are drawn. Objects inside the clipping region are visible; objects outside it are "clipped", meaning they're not drawn on the screen. In SL, when you raise or lower your draw distance, you're changing the size of the clipping region for your camera. Unless I misread you, clipping has nothing to do with what you were talking about. Please don't add potential confusion to the thread by using incorrect terminology.


In any case, I don't pretend to know what experience you have or haven't had with this or other engines. But what I can tell you is that the alpha sorting glitch does exist in every OpenGL application on this planet. Some realtime applications handle it better than others, but SL actually handles it better than most.

If you want an example outside of SL, here are a couple of screenshots from Maya. The two objects are both 1x1 poly planes, with a very simple 32-bit TGA applied.



In the panel on the left, can you tell accurately which object is in front and in back? I certainly can't. If anything, the "small" one appears to be in front of the "big" one.

But when you look at the panel on the right, you can see that the two are actually the exact same size, and there is considerable distance between them. The one that appeared to be small was way in the back, but it appeared to jump to the front from that particular camera angle.

Now, Maya is a very expensive, professional grade program, far more sophisticated in many ways than the game engines you mentioned. But it's got the glitch. And it's happening at a much greater relative distance than it probably would in SL. As I said, SL actually handles sorting pretty well, even though it's obviously far from perfect.




For sake of accuracy, so no one is confused, I should probably mention I cheated just slightly when taking those screenshots. Maya, as I said, is very sophisticated. It actually gives you the option of turning the sorting glitch on and off. It's the only program I know of that does. For the screenshots, I was obviously working without the correction turned on.

You might ask, though, if Maya can do it, why don't games, and why doesn't SL? Well, it's for the simple reason that Maya doesn't have to do anything in real time, let alone run a whole world . That's not what it's for, obviously. When it's using corrected sorting, it runs slower than when it's not. You can't tell the difference when it's just two little smiley faces, of course. But add in the amount of surfaces that are in a typical scene in SL, and it would start to crawl.

Pile on animated avatars, moving objects, particles, constantly changing scenery, and everything else the SL viewer shows you all at once, and you can forget it. While Maya certainly has the capability to run a world if you really wanted to do enough scripting to set it up, it would never be able to show it to you at speed. If you got one frame every few hours out of it on a home computer, you'd be lucky.

So give SL a break. It's doing a hell of a lot of things that no other engine does, and it at least holds its own in the alpha sorting department at the same time. I will agree that it could be better at sorting than it is, but it's certainly not a show stopper. It's a mild annoyance at most, and that's only if you don't plan for it.

Work around it or ignore it. It's that simple. Complaining about it accomplishes nothing, especially when you do it in the wrong thread.

I saved some tetures with transparency as PNG, from the GIMP. Two uploaded withall-white backgrounds, the third with an all-black background.

What did I do wrong?

They uploaded fine as TGA

It seems you had the Save Background Colour option checked when you saved the file. Open and resave using Save As and make sure it's unchecked when you want transparency.

Im sticking to tga, png has been nothing but annoyance and randomness when uploaded to SL.

Sizewise doesnt matter, SL compress it anyway.

I have follwed the PSP tutorial directions to the letter, and have read everyone's comments here about the program. Thus far, I have been unsucessful in turning a psp Tube of a gargoyle into a transparent figure in .tga/SL.

I start with a new layer, and place the tube in the middle of the layer. Then I've followed the directions in the psp tutorial here.

When I don't add the extra layer with black/gray background to dehalo, I end up with a black/gray background when I upload to SL. When I do add the black/gray layer, I get a black/gray background when I upload to SL.

I used SuS's method of selecting the background and deleting it. It did upload to SL with a transparent background, but ended up with a major halo.

I'm very new to SL. I've got a fair amount of experience with PSP, albeit not much with alphas/masks.

I'm pulling my hair out over this and have yet to have had a Eureka! moment on how to make it work.

Can anyone help? Can I integrate Sus's method with the flaming pear plugin? If so, at what stage do I apply the filter? Would I be better off not using a tube image?

. . . very, frustrated!

I too use PSP ( my version is probably pretty old too.) I think it needs a plug in or something to make the .tga 's keep transparency. I work around it by saving it as a .psd file, opening it in the Gimp and then saving it as a .tga or by just saving it as a .png in PSP which works fine as far as I can see.

I'm not sure exactly what "Sus's method" is, but from the sound of it, I'm guessing you're deleting the background, and then you're using the "from image" option to make your alpha mask. I'd be careful about working that way, for several reasons.

First of all, it's destructive, and that can lead to trouble. Never delete anything ever unless you absolutely have to. Masking is always a better way to go than deleting. You never know when you might need to recover something you thought you wouldn't need.

Second, it's not always so easy to select the background. If all you did was paint a simple object onto the middle of an already blank canvas, then sure, one click with the magic wand, and you've got it. But what if you want to extract something from a photograph? That kind of simple selection won't help you in that case. You're far better off devoting your time to mastering techniques that will work in all situations than forming your habits around crutches that only work sometimes. Painting a proper mask will always work; the magic wand can't always work.

Third, you don't have much control that way. What if you want gradients in your transparency levels, for example? That can be very time-consuming and difficult to pull off if you're not painting your mask yourself.

Anyway, the answer to your question is yes. You could certainly use the Solidify plugin. The time to use it would be after you've saved your mask to alpha, and after you've deleted the mask, just before you export to TGA.




Ingwaz, I'm afraid I don't have any experience with PSP's picture tubes. I've never used them. My understanding is they are somewhat similar to brushes. But that's all I know.

In any case, while it's possible that the tube is the cause of your problem, I would tend to doubt it. It's more likely that you're doing something else wrong. Here's an easy way to tell. Try making an alpha'ed image without using any tubes. If it works, then you know the tubes were somehow interfering. If it doesn't work, then it's reasonable to assume the tubes had had nothing to do with it, and that your problem is elsewhere.

Let's do something really simple as a test. We'll make the simplest alpha possible, just a big blank dot. Do this:

1. Make a new file. For this, the size doesn't really matter, but just to keep it typical, make it 256x256.

2. Create a new layer, and flood it with any color you like.

3. Apply a new mask to the layer. Then, using the circular marquee, draw out a large circular selection around the middle of the canvas. Fill the selected area of the mask with white, and fill the rest of the mask with black. In the end, this will serve to make the circular part opaque, and everything else transparent.

4. The next step is to save your mask to a channel. But before we do that, let's first make sure there are no other alpha channels already present in the image. If you have too many, the transparency won't take. You can only have one, no more, no less. Go Image -> Delete Alpha Channel, and in the dialog that pops up hit "Delete all alpha channels", and click Delete.

5. Now save your mask to an alpha channel, and you'll be sure it's the only one.

6. Delete the mask, and export to 32-bit TGA.

Now, got to upload the image to SL, and take a look at it in the preview window. If you did everything right, you should see a colored dot in the middle of an otherwise completely transparent canvas.

If that worked, now take that same image and paint something on it with tubes. Save out to 32-bit TGA again, and check it in the SL upload preview window again. Did the tubes change anything? Or do you still just see a big opaque dot against a transparent background.

If the transparency changed after you painted with tubes, then there's something inherent to tubes that interferes with proper alpha channel creation. Perhaps the tubes incorporate some unique form of masking or something, and PSP is having trouble keeping that information separated from the master alpha channel information. If that's the case, then I'd say avoid using tubes for now, until you can get some more concrete information on what's actually going on with them.

I suspect, though, that what you'll see is the transparency won't change. And if that's the case, just chalk up whatever happened before to user error. You made a mistake somewhere in the pipeline the last time around, and hopefully what you learned from this exercise will correct that.


Kaimi, if youre PSP version is extremely old, like more than 8 or 10 years or so, then maybe it's not equipped to save TGA files properly with alpha channels. I'm not sure when that particular ability was incorporated into the program.

What I do know for certain is that the methodology described in the tutorial here will work with versions 7 and higher. If yours is older than that, for God's sake, upgrade already! Frankly, I'm surprised it's even functional on a modern OS at all. If yours is newer than that, then the problem is not in the software, but in how you're using it. Try the simple tutorial I just laid out for Ingwaz. It will work if you follow it correctly.

Dang. What ever I am doing seems to be working fine for me. But now I have to read a lot of complicated instructions and upgrade my software.

Or lie awake worrying about it....

Yeah it's PSP7. Gee, it was so new and all when I got it...

Um, Thanks Chosen.

Heh, sorry if I talked you into complicating your life with a software upgrade there, Kaimi.

Anyhoo, PSP7 should work. Some of the menu layouts and specific wordings of tool names might be a little different, but all the same principles are there.

That said, you'd probably still find it worthwhile to upgrade. PSP really came into its own around version 9 or so. And it's only gotten better since. I really used to hate PSP (If you dig for some of my older threads here, you can find some that say as much), but when 9 came out, I changed my tune. Get a modern version, and you'll be amazed at how much more it can do, and how much better put together it is, than what you're used to.

What do you think bout The Gimp, Chosen? I have the latest version of that and I find it excellent for processing photos for my on-line album. But I need a tutorial for alpha channels.

Chosen... I've been reading through the various methods for making an alpha channel and I just wanted to ask you...what would be the best method to use for the following:

I'm trying to make a sheer top, with applique detailing etc....I don't want the applique to be transparent in any way. I had presumed that it was just a matter of changing the opacity on the 'top' layer, but all I end up with is a paler version of the original colour when I go to upload it. Any suggestions would be greatly appreciated...

I know I'm not Chosen but I bow down to him


On the Alpha Channel, make the top sheer by using a shade of grey. Then make the appliqué white on the alpha channel.

... of course thats if I understood you correctly.

Thanks Urah...I'll give that a go.....

GIMP is a fine program. It's not as powerful as Photoshop, but it's one of the closest out there. I personally hate its interface, but if that doesn't bother you, then there's nothing wrong with the program itself.

I'm not comfortable enough with GIMP to write tutorials for it, but others have contributed some good tips to this thread. You might want to scan through the various posts to pick up what you can.

Also, books on GIMP are now available, which I'm sure are a big help for many. If you think GIMP will be your program of choice, it's probably worth investing in a good book.

Sooner or later I'll get around to practicing enough with GIMP that I feel confident teaching it. But I'm not there yet.



As Urah said, if you want any part of the texture to be translucent, make that part of the alpha channel gray. The lighter the gray, the more opaque it will be; the darker the gray, the more see-through.

Remember, in any standard alpha channel, white means maximum, black means minimum, and all shades of gray are in between. In SL, the only thing we use alpha channels for is opacity mapping. So white means full opacity, black means no opacity (full transparency) and everything in between is translucency.

So, just as Urah indicated, you'll want the sheer parts of the garment to be gray in the alpha, and the applique parts to be white.

Thanks for the answer, Chosen.

Thanks Chosen......and Urah..

Hi
Does everyone use alpha channels?
I have been making clothes with varying degrees of transparency for a while now, and never used alpha channels.
No grey layers, it all sound very complex to me!
I just design, add textures, use as many layers as needed, adjust the transparency (which I can view in photoshop), then upload to sl.

Never had a problem

Am I missing something here?

Thanks very much for this...! Very useful for a newbie... (God knows I hate Photoshop.... way too much complicated for me...) But thanks to you I was able to upload my first transparent-background texture today.. thanks !

You're most welcome, Philippe. Glad to hear you found it helpful.