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Berlin Mesmeriser
Posts: 265

Why can you often see thru things that have no transparency ?

My partner and I built a large enclosed structure and there's a basement and a ground level area.  Lately when we walk on the ground level area we see thru to the basement.  I'm not talking about before things have rezzed, you don't see completely thru, you just see outlines of basement structures while walking and such.

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Caeldyn Vella
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Re: Why can you often see thru things that have no transparency ?

Reply to Berlin Mesmeriser - view message

Do you perhaps have the prims set at slightly transparent in texture tab?

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Rudee Voom
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Re: Why can you often see thru things that have no transparency ?

Reply to Berlin Mesmeriser - view message

There's a couple possibilities I can think of.

First, you can kind of see through anything including yourself depending on  your camera angle. Well, more like see inside it, but the effect can feel the  same, that a wall or something has disappeared. To see what I mean, stand next  to a wall then use Ctrl/left mouse to rotate the camera inside the wall. You'll  notice it's hollow and you're seeing inside it. But it's not invisible.

Second, if there's some other transparent or alpha texture in front of  another alpha texture there's a bug in SL that makes otherwise solid things  appear transparent. So if you have two walls with alpha windows in them it can  cause this illusion. Or some transparent prim that you don't know about or  forgot laying around.  To test this, click Ctrl/Alt/T and everything transparent  will glow reddish. Anywhere there's one of these textures in front of another  you might experience this bug.



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Aternia Afterthought
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Re: Why can you often see thru things that have no transparency ?

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I had this problem as well in my shop when I was testing out my textures on the wall.

After fighting with the structure, textures, settings, etc for over two days.. my girlfriend helped me figure it out.

Previous to the viewer upgrades, you could use .png textures, even for solid designs with no alpha areas. However, now in order to use them they need to be flattened first. If you leave them as a layer when you save the .png, then SL has bleed through even though your texture is not transparent at all. So you either have to save your texture as a jpeg or tga.. or flatten image on the png before uploading

That was such a pain to figure out, it wasn't until my girlfriend asked if I was using pngs or jpegs. I was like well, I'm not certain but it shouldn't matter because these textures worked months ago just fine when I used them last. But sure enough when I tested a different texture that was a flattened png, it worked fine. I tested a tga and jpeg, those both worked fine. But my layer 0 png was trying to create an alpha section. So once I flattened it and turned it into a background image in photoshop, I uploaded into SL and ta-da worked fine.

I hope this is the same problem you had, so that it solves it for you

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Re: Why can you often see thru things that have no transparency ?

Reply to Berlin Mesmeriser - view message

Are the outines "lit up?"

If so, what you may be seeing is the actual selection outlines. Viewer 2 (in particular) has a bug when you select an object, closing the edit window may not deselect the selected item. If you were to then click on a wall or floor to clear that selection, you might just transfer that selection to the whole house.. resulting in the whole structure being "outlined".

It would help us a lot if you could attach a screenshot of the effect, then it would be a lot easier to diagnose the problem instead of taking wild guesses.

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Re: Why can you often see thru things that have no transparency ?

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Aternia Afterthought wrote:

I had this problem as well in my shop when I was testing out my textures on the wall.

After fighting with the structure, textures, settings, etc for over two days.. my girlfriend helped me figure it out.

Previous to the viewer upgrades, you could use .png textures, even for solid designs with no alpha areas. However, now in order to use them they need to be flattened first. If you leave them as a layer when you save the .png, then SL has bleed through even though your texture is not transparent at all. So you either have to save your texture as a jpeg or tga.. or flatten image on the png before uploading

That was such a pain to figure out, it wasn't until my girlfriend asked if I was using pngs or jpegs. I was like well, I'm not certain but it shouldn't matter because these textures worked months ago just fine when I used them last. But sure enough when I tested a different texture that was a flattened png, it worked fine. I tested a tga and jpeg, those both worked fine. But my layer 0 png was trying to create an alpha section. So once I flattened it and turned it into a background image in photoshop, I uploaded into SL and ta-da worked fine.

I hope this is the same problem you had, so that it solves it for you

I've written on the subject of texture transparency (and its related issues) literally hundreds of times, and I've even  been published in books on it.  I'm sure your girlfriend is probably an intelligent and wonderful person, but I do have to point out that she's been misinformed on this issue.  The PNG file format itself has nothing to do directly with the issue in question, and flattening doesn't affect it at all.

As best I can tell, the reason for the relatively common misconception that flattening is a necessity can be traced back to a  single online tutorial that was written 6-10 years ago.  The author, for  reasons that escape me, included a flattening step, just prior to the  output step.  Somehow, this tutorial became a popular read with early SL  users.  Subsequent tutorials written by some of these users were then modeled upon it.  One thing lead to another, and all of a sudden, flattening  became "necessary" in the minds of an awful lot of people, event though it never actually was, and never will be.  "I read it in ten different tutorials" can be a powerful convincer, obviously. But that doesn't make it actually true.

Here's why flattening doesn't actually matter.  All of the image formats that SL can import are inherently flat.  They have no layers in them.  In this context, layers only exist in your working document.  The outputted texture image (PNG, TGA, BMP, or JPEG) will absolutely flat, by definition.  So, whether your working document has just one layer or a hundred layers or a million layers at the time you spit out that PNG, it won't make any difference.  The PNG will come out exactly the same either way.

Now, here's why PNG can sometimes be problematic as a source format for texturing.  It supports multiple forms of transparency.  Therefore, if so much as a single pixel is anything less than 100% opaque, the entire image is considered transparent.  The pixels that are fully opaque then have a transparency value of zero, which is not the same thing as having no transparency at all.

When you bring imagery that contains transparency into a 3D environment like SL, you end up with render sorting problems (the "alpha sorting glitch").  It makes no difference whether the source format was PNG or TGA.  In fact, your source image never even leaves your hard drive.  When you upload an image to SL, the viewer creates a JPEG2000 copy of it, and it's that copy that gets uploaded.  So the source format never even plays a direct role in anything that goes in in-world at all.  But even if the actual source image itself were uploaded, the same problems would occur.  It's the bit-depth of the texture that causes the problem, not the file format.

To ensure your opaque images don't have sorting problems, you must ensure they are saved as 24-bit images.  It's easy to do that with TGA, since you can just make sure there's no alpha channel, and you're all set.  PNG lends itself a little more toward user error, since as I said, it supports multiple forms of transparency.  The very careful, and well educated, user will never have a problem with it, but most people aren't necessarily that careful (even professionals).

If you do want to use PNG, the easiest way to make sure transparency is not present is to use the Save For Web dialog in Photoshop instead of Save As.  When you use Save For Web, there will be a checkbox to include transparency.  Uncheck that, and all this becomes a non-issue.  Just remember to do that every time, and you'll be fine.

Rudee Voom wrote:

Second, if there's some other transparent or alpha texture in front of  another alpha texture there's a bug in SL that makes otherwise solid things  appear transparent.

Just to clarify, this is not a "bug in SL".  This is an inherent property of how realtime 3D graphics works.  The sorting glitch is present in nearly all 3D applications, from freebies like SL, to video games, to high end modeling programs that cost thousands of dollars.

The reason you don't see it in games is because professional game artists are well aware of it, and they go to pains to work around it.  They simply don't overlap their 32-bit textures.

The reason it's all over the place in SL is because most of SL's content is created by amateurs who don't know any better.  They do things that one just shouldn't do, and then they think SL must be broken somehow.  Also, in a dynamic world like SL, with thousands of concurrent users, there's always the possibility that even if you do everything right, someone else in the neighborhood might not, and their build can screw things up for you.  And of course, there's always the dredded hoochie hair, which can cause problems for anyone at any time.

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Pickle Soup
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Re: Why can you often see thru things that have no transparency ?

Reply to Berlin Mesmeriser - view message

Chosen, if you have an image that does have some transparency in it, but you don't want the entire thing to be see through, can you still use the 'Save for Web' feature? Or is that just for PNG images that are not transparent at all?

Sorry, maybe that's a dumb question.

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Rolig Loon
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Re: Why can you often see thru things that have no transparency ?

Reply to Berlin Mesmeriser - view message

If your texture is supposed to have any transparency in it at all, it has to be saved as a RGBA image (that is, as a 32-bit file). If you have only 24-bit density, there's no place to carry transparency information into SL. By creating your alpha channel properly (or doing the equivalent in a PNG image), you can vary the transparency information from one pixel to another in the image, but every pixel has to have those 8 bits for storing the information. If you "Save For Web", you'll end up with a 24-bit image .... and no transparency anywhere.

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Asami Imako
Posts: 273

Re: Why can you often see thru things that have no transparency ?

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A much easier way I've found, for the common everyday SL creator is once you've saved your png image, to simply open it in GIMP, right click on the layer in the layer dialog, and select "Remove alpha channel" and save it again.

It's worked 100% of the time I've done it that way, regardless if I saved it using Photoshop, GIMP, or anything else.

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Aternia Afterthought
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Re: Why can you often see thru things that have no transparency ?

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You misunderstand. What I was saying is that my girlfriend was throwing ideas at me and asked if I used jpeg or png. From the start, I told her that wasn't it. I had used these textures (from various sets, people, self-made, handmade and photograph-made) about six months ago without any problems. This is why it took two days to fix the problem because I didn't think it was the textures that were proven to work in the past just fine and it was not something I overlooked, its impossible to overlook something like that. However, while I was thinking up other ideas at that point, I opened my original texture that I made for SL, in photoshop, and I noticed it was a layer (unflattened). I thought.. well I tried everything else.. so I looked up my other textures and found one that was a background image png. I checked my SL inventory, took that one out in SL and tested it.. no problems.

So I took my original png, flattened it, uploaded it and the problem was fixed. My problem exactly is the way that unflattened pngs are working with each other. This DID NOT happen in the past with these two textures, because these textures were used the same way yesterday, that I had used them in the past. They are the textures for my store and I was remaking my store but wanted to use the same textures since I like the color scheme. So thats how I didn't overlook it and did notice it didn't happen until recently.

Saying that flattening has nothing to do with it, when it took the transparency away from both, despite your books and years experience with it, seems off. I would have normally said that flattening wouldn't fix it, but recently this is how the pngs are working with each other. I'm not debating that even though you think an image is solid, it can very well have a transparent pixel in it. I'm saying that flattening fixed whatever was causing transparency in my solid images. I will go and reproduce the problem and take screenshots.

So its hard for me to accept, you telling me that this did not fix my problem.. when me and seven others watched my test between two identical prims, with a flattened and unflattened png of the same texture on them.. and saw it fix the problem I have since taken all the original textures (not the broken ones saved from SL) and flattened them.. re-uploaded.. and started building with them again since they are fixed by that

*shrugs and smiles* I just want someone to figure out why its doing it all of a sudden. Bug? Someone change something in the upgrade because of the new alpha layer? Eh. I'm glad I found the way to fix my problem.. but was really miffed over having to reupload everything.

Here is my reproduction of the problem and the screenshots to show what fixed it

http://www.silentmisery.net/PNGReproduction.jpg