Prim drift

It's only happened once or at most twice to me that I've had prims aligned to my mind perfectly and they've changed.

In one case I know that I aligned two pieces by copying numbers, and the numbers on one piece were slightly different when I took the structure out of inventory later on.

Someone called this "prim drift" and a friend theorizes that the virtual wind knocks prims out of alignment - seems unlikely to me (because the effect would be uniform).

Have other ppl noticed this? and does anyone know why it happens?

I'm just curious btw.

My theory is that these numbers go into and get fetched out of a database and probably not stored in the format we see. Maybe some rounding or formatting changes them at times?

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I think I remember reading just that somewhere, the round error. To get the best precision I think the recommendation is to use whole numbers and zero rotations so that the information will be preserved and not loss due to rounding or rotation calculations.

it's rounding errors, it can be seen more frequently if you move items via drag handles using the numbers at the top of the screen.... I set the same 3 prims to a position multiple times before they behaved and kept they positions. and I wont even go into my issues of link set centers and rotations...

Type the numbers in -- two prims may show the same number, but one is rounded up and one rounded down to that number -- and use one of the new viewers that has another decimal place for more precision. Then lock it!


Prim Docker used to work for me, but then mysteriously stopped -- but I see a new version advertised. Well worth the money.

Am I remembering correctly that one of the alternate viewers has extended decimal points? Does anyone have firthand knowledge?

That's what I just said I use Emerald and Snowglobe, and either one or both have it.

Prim.Docker was broken by H4, but the creator has kept shamelessly flogging it. The new version is no better, but now has a few added bells and whistles, which work, sort of, but are not related to to prim docking, and in most cases are better and more easily accomplished through the regular edit window. In any event, Prim.Docker will not work on any prim smaller than .050 along any axis. With a .049 prim, it leaves a .005 gap, and so on.

Prim Master, on the other hand, does everything it claims to. It will snap a .010 prim right up against a 256m prim, reliably. If you want to dock prims, stay away from Prim.Docker, I used it for years, now it is broken. Prim Master works.

As far as prim drift goes, over all the years I have been building, I have never experienced it, at least once the prims are linked. I occasionally move prims, only to have them snap back to their original position as soon as I let go of them. This can be a huge pain. However, once I get them to stay put, and link them, I never experience this slow and nebulous drift people speak of.

Lately, however, I have become aware of a group of builders who, apparently rather than linking things, coalesce them, which makes no sense to me at all. But this is what they do, and they apparently trust the SL servers to keep accurate copies and positions. This, to me, is insanity.

Perhaps in non-linked objects, prims drift. I have NEVER had prims drift in non-scripted linked objects, however.

Quite awhile back, I built a train. When I rezzed it recently, I was appalled at how far off center some of the prims were. Some of them were as much as .012 off. I could have blamed this on prim drift, but the actual problem was that I had eyeballed things into place, and the prims were actually exactly where I had put them.

I think that this is where the idea of prim drift actually comes from.

Hah - I didn't see your reference for some reason. I was thinking back to some half-remembered old viewer

Since I posted this question, I found a way that I may have inadvertently moved prims without realizing.

Sometimes while editing, if the focus is on the edit window, and I move my arrow keys (meaning to move myself) I change the values for some aspect of the selected prim. If I don't happen to be looking in the right direction, I miss it, and later on look at whacky numbers in the spaces where I am SURE I wrote them correctly, or bizarre angles that I never would have chosen.

However, builder friends told me of prim drift, so I assumed it wasn't ME that made the mistake.

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Yeah, this is my take on the whole prim drift thing. As a different but similar example, a friend of mine, shortly after she got to SL, was making prim skirts. She did so by making a central prim, rotating it, and attaching the skirt panels to it. She insisted that SL was randomly repositioning the axis of rotation, and I told her that no, she was moving it herself. After several such exchanges, she decided to follow my advice and rotate the linkset by the numbers, instead of by grabbing and turning it, and was shocked to realize that she had indeed been inadvertently moving the linksets laterally.

There are indeed SL related problems when it comes to building, but I maintain that random prim movement is not one of them.

I've had a problem recently I'll call rotational drift. I have a large building with several linked prim sets of up to 70 or 80 prims each. Some of the treatments include octagonal pillars (8 triangular prims) I created using ShapeGen0.95.

I find that the pieces of the octagonal pillars will drift in rotation by 0.05 degrees. Example:
<0, 270, 90> drifts to <0, 270.05, 89.05>. Other pieces in the link set are affected occasionally as well. I don't know if this happens when I link the prims, if I'm dragging my mouse at the wrong moment, or something else. I'm keeping an eye on those suckers, though. Has anyone else experienced this "rotational drift"?

If you work with small enough prims, zoom in, you can actually SEE the prims "twitching" a little bit.

There's definitely something going on that's not entirely the builder's fault.

I thought prim drift was an artifact of using floats.. Something about numbers of the right side of the . getting less resolution as numbers on the left side get bigger.. Or something.

That Emerald lets me use 5 decimal places when SL only seems to grok 3 is one of the very, very few things about Emerald that bugs me..

Hah! Twitchy prims are not cool.
I learned this the hard way, Do Not try to edit *tiny* prims up in your super high skybox.... Something about the sims ability to place things well that far from 0,0,0 is very broken.

No, it is not.