Alpha Channels Getting Confused?

Why do sections of images sometimes disappear or seem to change position in SL?

This phenomenon has to do with a glitch common to nearly all 3D applications in what’s known as alpha sorting. It happens in nearly all video games, and even in high end 3D modeling packages costing thousands of dollars. What happens is when two or more 32-bit images are placed so that they intersect or overlap in close proximity, the renderer has trouble determining which one to draw first. As a result, the images can appear to flip-flop their positions in 3D space, to cancel each other out, or to otherwise behave strangely.

The way to cut down on this is to make sure that 32-bit images are only used when absolutely necessary. Images that do not need transparency should always be saved as 24-bit. Beyond that, there are certain building techniques in SL that can minimize the effect, and others that actually take advantage of it, but building is beyond the scope of this guide. There are plenty of tips about this on the building forum.