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Is it possible to enable physics/flexi for linked prims?

Suki Hirano
冬の温暖
Join date: 30 May 2008
Posts: 172
12-06-2009 12:49
I was wondering if it's possible to enable things like gravity or wind effects etc, for objects that are linked together? For example, I want to make a little accessory on my belt that consists of a fine chain, with the two ends attached to the belt, and in the middle of the belt are some beads and a little doll. Is it possible to make the chain have gravity (form the natural U shape, like a necklace), and swing around when walking, with the attached accessories still in place on the chain and all the chain links of course not out of order?
It's hard to explain what I mean so here's a picture:



Imagine the paperclip is a belt, and there are little accessories attached to the chain.
Thanks.
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Rolig Loon
Not as dumb as I look
Join date: 22 Mar 2007
Posts: 2,482
12-06-2009 13:07
You can get that effect under some circumstances by attaching the -Z ends of two flexi prims to each other and giving each of them a little bit of negative gravity so that the loose ends float upward in a catenary arc. If you're careful and only make the linkset very gently responsive to wind, you can make it look as if the thing is swinging from its endpoints, even though they are not attached to anything. I've done that to make a flexible rope appear to hang between two posts, for example.

Unfortunately, you can't use that trick on chains that you are going to wear because the loose ends of the chain will end up swinging unpredictably as you move. When that happens with a big rope hanging between fixed posts, you can hide the fact that the ends are moving instead of the bottom of the arc. It makes a great illusion. On a moving avatar, though, the illusion simply wouldn't work.

I don't know of another good way to get the effect. Sorry.
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Void Singer
Int vSelf = Sing(void);
Join date: 24 Sep 2005
Posts: 6,973
12-06-2009 20:42
you can also texture the whole hanging portion onto a single flexi, but it will be flat, and the motion may be a bit odd at some angles.
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Ceera Murakami
Texture Artist / Builder
Join date: 9 Sep 2005
Posts: 7,750
12-07-2009 06:46
Unfortunately, flexi prims do not support linking both ends to something, and having the slack prim hang naturally in a catenary curve. The problem is that a prim has only one point to designate as it's attachment, and the flexi action is all client-side illusion. So you can't make a flexi-cylinder and fix both ends to something, nor can you attach a prim to the moving end of a flexi anything.

When making flexi tails and other things that have multiple flexi prims you keep the settings for gravity, stiffness, wind and the rest all the same for the congruent parts, and that makes the parts all seem to move more or less as a unit. But it can still be way off.

The trick mentioned above of using two flexis with slight negative gravity is certainly an intriging one. But it would be almost impossible in most cases to keep the moving ends from seperating.

As Void suggested, for the accessory pictured, I would use a flat flexi for each chain loop, textured with the curved loop of chain. Yes, it will have no thickness. And it may look off from certain angles. But it is as close as you are likely to get, and the level of detail accuracy is sufficent for all but a very tight close-up view.
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