Transparency and Clipping Issues

I have been trying to create a realistic looking rose and no matter how I try to create it (one prim per petal, one prim per concentric row of petals) i keep running into clipping problems where the petal that should be in the background is instead overshadowing the objects in front of it. This only happens when I use textures with transparencies in front of other transparent textures.

Is this a problem with my video card, second life software, or my eyes?
Does anyone else experience this?
It seems to be very consistent on my screen and it happens from all viewing angles.

Thanks,
Dae

What you're seeing is a problem in SL with what's known as alpha sorting. This is an OpenGL issue, which is extremely common in video games and 3D modeling programs. When two objects with transparency (alpha) are placed near eachother, the viewer has trouble determining in what order to render them. Usually it will render whichever one is most perpendicular to the camera as "in front."

Annyoing as this is, some objects are built specifically to take advantage of it, such as trees, bushes, fire, fog/light effects, clouds, etc. For your rose, you're going to have to find a different way to go about building it. The most common way to do it is to place a profile shot of the flower on 6 or 8 different flattened, intersecting cubes, the same way the plants in your library are built if you examine them carefully. Actually building the petal structure would take an enormous amount of prims.

I hate this effect also. I would like to know some more detailed tips/tricks/workarounds in overcoming this problem when needing to use alphas. Anyone mind sharing some more experience on this? Thanks much.

I have a small rose that was given to me. When I looked at it up close and "Edited" it, I saw that it was nothing but a series of colored prims linked together. Very elegantly done, no textures, just green & red prims.

When alpha sorting ruins your day, it's time to find a new way

I'm afraid that I don't know of any good workarounds. The thing is, it all depends on the viewing angle.

So you can get something that looks great from one angle, and from another it will be all wrong.

As far as I can tell, and I could easily be wrong, it seems to sort correctly when the viewing angle places the center point of the object that needs to be "in back" lower than the center point of the one that needs to be "in front." But that could just be coincidence, based on some other facet of the test objects I was using, and not a real thing.

The only thing you can really do is interpose a surface that has no transparency between the two transparent surfaces. That will stop the alpha sorting problem. But it will also stop any possiblity of transparency, so it's not always a good solution.

On the plus side, most residents have gotten so used to the problem that they barely see it.