Texture problems with builds

This may be in the wrong discussion, but I was wondering if anyone has ever had any problem with textures "overlapping" each other. Not the overlapping where the prims will flicker, but the overlapping that will make parts of other prims "disappear" and look invisible? It only seems to happen with certain textures. Is this a bug in SL? Is there a work around?

Its a common problem that the end user cannot fix. It's caused by how the current engine sorts 'alpha' transparency, and is the same effect that causes two transparent prims to switch between which shows better.

It is caused by 32 bit textures, even if no alpha channel is present (Alpha channels are what cause some areas of a texture to be transparent normally) overlapping. Since the engine doesn't know how to properly sort them, it renders them incorrectly at some angles. The only way to avoid this is to avoid overlapping 32 bit textures. I can't remember how to find out if a texture is 32 bit at the moment, CHosen Few once said how and I've forgotten.

If you have two partially transparent (As in only part of it is transparent) textures, they will do this at some point, as they are always 32 bit.

Its a problem that is currently just plain annoying, and also currently impossible to fix on the client side.

What you're describing is called the alpha sorting glitch. When two or more surfaces with 32-bit textures on them overlap in close proximity, the renderer has trouble determining which one to draw "in front". Usually, it will pick whichever one has its center point physically closest to the camera in each frame. That may or may not correspond with what you as a human being consider to be "in front" and "in back". As you move the camera around, the positions of such surfaces can appear to flip flop in 3D space as one or the other becomes closer to or further from the camera.

The glitch is common to nearly all 3D applications, not just SL. The reason you don't see it in video games is because game artists know how to work around it. Since SL is created primarily by amateurs, most of whom learn as they go, and some of whom it seems never learn at all, many people don't understand what the problem is, let alone how to avoid it. So you see it all over the place.

The solution is twofold. First, make sure you never ever use 32-bit textures unless you absolutely positively need transparency in the image. It's common for those new to texturing to assume "more bits" must somehow be better than "less bits" so they save everything as 32-bit at first. Don't do that.

Second, when you do use a 32-bit texture, make sure you don't put a second one immediately behind it. Sometimes this means you have to alter your original design plan. That's OK. It's better to have a slightly altered build that functions properly than a true-to-plan one that doesn't. You just have to resign yourself to the fact that certain things cannot be done.

Realize also that the glitch provides for certain advantages. Without it, common objects like trees, plants, fire, etc., would have to be made very differently than they usually are. The glitch allows you to do things like make a whole tree out of just 3 intersecting planes instead of having to physicallysculpt it out thousands individual prims.

These techniques are not just for SL, by the way, but for pretty much all 3D applications. Do you play World of Warcraft, for example? Take a look at the bushes in that game some time. Inspect them closely, and you'll see they're all just intersecting planes, made the same way people commonly make bushes in SL.

Discovering how to work around, and work with, the glitch is an important part of learning how to model and texture for any realtime 3D environment.

So much better explanation and only slightly more time than me (Even with more text..)..I envy you XD

Eh, I've probably written that same thing, or something similar to it, a thousand times by now. It's good to have differently worded explanations of the same thing though, so don't beat yourself up. People don't always learn effectively from the teaching style of any one person. The more, the merrier.

Lol..everyone learns from you and you know it =P

ANYWAY..yeah, those two explanations should be sufficient.. if not then.. umm..well... here's yet another (No, I'm not calling anyone stupid..quite honestly I'm really really bored at the moment)



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They don't work because of the transparencies. The current rendering engine in SL doesn't know how to sort transparent things correctly so messes it up at some angles. There currently is no fix for it.

Hi Chosen,

Could you elaborate on this technique a bit? I have tried to use the tree trick to "create" a 3-D looking version of a cell and it wasn't very effective. I don't know if I was doing it incorrectly or that this particular shape doesn't lend itself to this technique.

I took a picture of a cell (scanning EM of a Sertoli cell - pictures attached), hacked out the extra stuff and made the background transparent in PS, and then tried to create the tree-like fake 3-D version in SL. It just looks like, well, several flat panels - no illusion.

Is there a trick to the trick that I'm missing?

Thanks,

Doug

It's not always going to work well for all images. Generally, something spindly and branching like a tree, abstract and flowing like a flame, or fairly uniform like a hedge bush, will work better than anything compact and well defined like that cell.

The parts of the "back" planes that show around the edges of the "front" plane should be able to add to the image, not compete with it. If you can see extra branches on a tree, for example, it doesn't destroy the tree; it just makes it look even more full. With that cell you've got there, Doug, it doesn't look like that sort of illusion would work very well. If it were a cluster of lots of cells, maybe, but not just the one.

In any case, the illusion is never perfect. It's generally convincing enough for people to know what the item is when they look at it, but it's never fool proof. You can break the illusion pretty easily on even the best one simply be looking at it from the wrong angle. Games can compensate for this by restricting your point of view. SL really can't.

OK, I was sorta afraid of that.

Thanks (again) for taking the time to help me out. You certainly do make a huge difference to us here in the forums trying to find our way.

Doug