Have you ever noticed that sometimes while you’re building things, the prims seem to bounce? I’m not talking about physics, or that lovely little checkbox in the Emerald preference settings that enables the almighty jiggling boobs – I mean that kind of constant, erratic shaking that seems to torment prims? You’ll notice it the most when you work high in the sky. I tend to keep my building platform (and the mess that lives on it) thousands of meters in the air. Tonight, I was working on some very tiny prims and they just would NOT hold still. I off-handedly whined about it to my very smart friend Eddie Optera, who works in 3D and visual effects for a real life living, and he had this very informative and interesting answer for me:
It’s most likely a floating point rounding error – large magnitude numbers have less decimal precision, ie., the farther you are from the origin the less control you have over granular movement. You see, the center of a prim moves with the prim, but the prim is located relative to the origin of the world. It has a center, but that center is at (x,y,z) relative to the worldspace origin. Way up in the sky, you’re far away from that origin. Conceivably, if you found the center of the world at sea level, it wouldn’t bounce at all.
It’s a super-common problem. Every piece of software in the world suffers from it to some degree. Visual effects people will talk about scenes with continually moving objects, like a jet plane or a car, that they had to write code that would update the position of all of the items in the world on each frame so that they still had granular control of the location of the hero object at the end of the sequence…(on each frame or each shot, depending.)
In Maya, for instance, at the origin you can move things at tiny fractions of a millimeter. But a few kilometers out, they’ll move a foot at a time. Which is perfectly fine if you’re just sitting a building somewhere off in the distance. But if you’re trying to animate a character it blows.
So there you have it. I like to think of it as the wholly untrue “virtual gravity gets stronger the higher you fly,” but the short answer is, “Move your workspace closer to ground level.” Thanks, Eddie!
