Alpha Channel Frustration

I understand the concept of Alpha Channels. I know what they do, and I know how to make one. But I've never seen a tutorial of alpha channels on an actual garment.

I'm having problems with filling the template smoothly.
Sience magic wand has shown the worst results, I've tried ctrl+layers, with both SL's, Chips, and Robins template. But i just can't seem to get the alpha smooth and without glitches.

I've heard channel masks is the best way, but i haven't found a tutorial on this.

Any tips? =/

Have you tried at the top of this forum, which discusses them in the context of SL? There's also been a discussion about it recently in [url=http://forums.secondlife.com/showthread.php?t=143200]this thread[/url] towards the bottom.

Post 13 et seq. in [url=/109/b7/80285/1.html]this thread (in the stickies under Robin's tips and tricks)[/url] also deals with making and using alpha masks for a while.

I don't know what software you're using. I'm using Photoshop CS, and what I usually do is I create the shape of my garment (which, most of the time, is exactly the same shape as the alpha channel) by using the Path tools.

This allows me to :
- apply filters, colours, textures... you name it... directly to the Path ;
- select the Path with one single click, and use this selection to create your Alpha channel
With this method, you'll have an Alpha channel with the same shape as the garment.

If, for example, I want a hole in my tee-shirt, I draw a circle with a Path, select it, go to the Alpha Channel, and paint the inside of the selection black.

I hope I explained this properly. It's much easier to do than it sounds.

I tend to define my own alphas using a combination of selection methods, including magic wand selection, clipping masks, quick masks and pen tool selections.

In particular, quick masks (hit 'q' to activate the quick mask mode for a selected layer) are fun because you can essentially *paint on* your selection as if you were painting on masking fluid. If you want something sharp, use a 100% opacity pencil brush to block in the areas that you want, then use something smoother like the pen tool to select curves and clean off your edges. Once you're done painting on the quick mask, hit 'q' again, and photoshop will have selected the mask for you. If you want to keep that quick mask, create a clipping mask by holding down alt and clicking on the clipping mask button on the layers palette.

In relation to Robin's template, I tend to magic wand (0 Tolerance, Contiguous) the 'non' clothing part of the "Match Outline" layer, then invert my selection, subtracting from the selection as necessary with the use of alt+lasso.

Once I'm almost ready to finish, I go back in to my channels palette, turn off everything except the mask, select the mask and invert that selection.... and then i go and create my alpha.

Things usually turn out ok. Was there something specific about selections you were having problems with? If you like, I might be able to take a few screencaps to go in to this in more detail.

//edited to correct terminology.

Thanks for answers! (i use photoshop CS2)
Basicly i just want the original whole template shape filled with white. I know Robin's Tshirt tutorial has one, but i would like to know how i can do this.
Cause the ones i make (with ctrl+seam matching guide and then fill out the rest with brush) end up like this:

with glitches and lines as you see =/

It looks like your selection is for the insides of the Match Outlines template only.

I've found selecting the outside and then inversing the selection solves this, since including that extra outline takes care of any overlap that may happen. It's a pain to have to start over again, but it makes all the difference when you get to your final product and don't have those stray pixels of stuff you don't want.

Yes, i've done that. But you've got to use the magic wand, which makes the alpha fussy around the edges. But maybe you wont see that ingame?
If you invert with match outlines, it will only be possible to draw on the background, and the innder area of the garment.

I did it now!
I ctrl+click Match Outlines and then select-expand-contract.
Thank you all for helping.

Hrmm... if it helps any, you may want to enlarge the image size of your template for working files (and reduce them to 512x512 later). This will give your magic wand selection more pixels to work with. Also make sure that your anti-aliasing is off so that your selection edges don't go fuzzy. If you select from outside of the clothing, then do the selection inverse, you'll get more of a selection than you need, but it's better to have overlap than not enough pixels to cover the entire garment.

Remember to always include about 5 or more pixels of bleed over the edges of the wireframe guide in your alpha channel. This will reduce the chance that seems (from background bleed) will appear while viewing the texture on an avatar in SL or your favorite previewer.

Based on what I see happening at the shoulder seems in the posted image, your background is bleeding into visible areas of the texture.

Actually, I thought i did it. The glitches just became smaller:

I expanded the alpha a great deal:


But the glitches comes anyway:




... help?

Aya, like others have said, it looks like your edges are simply too close the outlines. And i'm not sure why you are trying to mask out the non-outlined areas. You do not need to alpha mask the area between the outlines because of the nature of the template, it will never show. Sorry if you already know that, just stating that to make sure.

Instead, only worry about alpha masking the parts of the template where you want skin to show (or sheer areas), like the neck and hands. And for any fabric that goes to the edge, draw it well past the outline just to make sure it doesn't have holes or raw areas on the seams. Another benefit to drawing past the outline is that as clothes rez in, they will look better because the blurred edges are uniform.

So draw your fabric edges past the outline and don't worry about alpha masking them.

For instance, here's a sweater shrug I designed a LONG time ago. I have the outline edges showing so you can see where it is (plus a copyright watermark which is not normally there). Notice how all my fabric edges are drawn a good bit past the outline.




And here's the alpha channel for the shrug, with the outline edge turned on for this example. All I worried about alpha masking was skin areas.




I hope that helps. Let me know if you still have questions, etc.

Aya, for what you're doing, I'd suggest using the alpha channel subtractively instead of additively. You seem to be wanting to use it to fill in the opacity rather than to cut out the transparency. I'd recommend going the opposite route. Start with a completely white alpha, so everything is opaque. Then selectively fill in the transparent areas, and only the transparent areas, with black. That will completely eliminate the seam problems you're showing in your picture.

Just so you know, there's no need for all that black in the empty parts of the canvas. Nothing of those parts gets mapped onto the avatar model, so bothering to make them transparent is really just a waste of time. Notice in Blaze's example, everything is white except the specific parts of the garment that are supposed to be invisible.




If your goal is to make a full-coverage garment with just a little transparency, maybe just to cut out the neck line or something, then start with a totally white alpha, and paint the neck area black. If it's something that doesn't cover much, like a bikini, then start with a black alpha, and paint the bikini area white. The idea is flood the canvas first with the dominant level of transparency, and then fill in the details afterwards.

Hope that helps.

Let's look at 2 things:

A: The background should be as neutral to the visible area of the texture as possible. Compare figure 1 to figure 2 below. Figure 2 is more neutral.

B: Bleeding your visible texture over the template boundary by several pixels will greatly decrease visible seems, especially if your texture has high contrast detail, as in this example. Your expanded alpha channel can be used as a guide. Bleeding the texture can be accomplished by duplicating your texture layer twice and running a motion blur at about 5-10 pixels on each layer. One layer should recieve a vertical motion blur and the other a horizontal motion blur. Both layers can then be merged and duplicated a few more times to strengthen the effect. See figure 3 and 4 for an example of this. The green boundary is the area between the normal region and the expanded alpha channel.