Hinges and nonCOG rotation

Hello,

Been looking around all morning and I can't find this one so excuses if there is duplication etc.

I need to rotate a prim on one *edge* as oposed to the COG, so I have heard that there are "hinges" and have gleaned a bit of info on how they work but not enough to get me there.

If someone could post a brief review I think us "new people" (not quite newbie anymore) would certainly appreciate it.

If it helps, what I am making are regular geometric solids (Icosohedrons and Dodecahedrons) from 10m pieces.

Perhaps someone has already done this and knows all the tricks but I am finding it very difficult mainly because it involves exctly the kind of raotations mentioned.

It didn't help that the building tools changed halfway through my project either.

I am currently assembling and positioning by hand around a "Phi" structure of three interlinked golden rectangles.

This will work,... but the tolerances are small and the positioning tedious.
A hinge would work wonders if it is useable and (later) removable. Remember I currently know little about scripting, so I need a better explanation than "look at this script."

Thanks for any help, either answer here or IM me in SL.

Dianne Mechanique

Searching on "hinge" I got a few relevant articles. Here is perhaps the most useful:
/54/e1/35124/1.html


Apparently hinges are not very reliable, and people are hoping that Havok 2 will help matters. Instead of using hinges, the general technique is to cut the object so that its center coincides with the new edge, and then do the usual rotation. Seems there ought to be a way of changing the center of rotation by shifting the local center of the object, but I see suggestions that this is not possible either. So you have to do the appropriate translation/rotation/translation in world coordinates.


You've got my attention. I love building those structures. Ever done a Rhombicosadodecahedron?


Sounds like it will be worthwhile coming up with some building tools that compute the proper translations and rotations for you and move objects into alignment. I will be happy to work with you on that, as I need to understand the very same thing for one of my projects. I'll be looking for you.

First of all, thanks ever so much for replying to this thread.
I thought the lack of answers was due to the typical "emabrassingly stupid question" effect.



Unfortunately, you cant get an equilateral triangle of any size doing it that way.



I tried extending a thin"stick" out from one side of each triangle so that the COG was on the edge but that didn't work. I think the tools might have been changed almost at the same time I was doing that however so I might have been wrong about that.

I think my problem is basically just inexperience with the tools. For instance I think I must have been the last person to know they changed them. Also "hinge" is a menu selection (if it's the same thing) and I hadn't noticed that or I probably would not have posted the request.

The whole deal with rotations is hazy to me as well as the difference between "world" and "non-world" coordinates, and not for lack of trying to analyse the thing. On the other hand I am sure in a few months I will be amazed at how foolish I was (now) when the solutions are likely obvious.

It was also a great surprise to me the first time I put a grid texture on a block and watched what happened to it when I "clipped" the edge. Who would have thunk that rather than being clipped the block is actually collapsing in on itself? Lots of this stuff is non-obvious to newbies like me.



Yes. I have found the "ringmaker" and "shapemaker" tools invaluable. Something like that for geometric solids would be a godsend. Unfortunately again, database scripting is about as "codey" as I get so I would not be much help in designing such tools.