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Prim Rotation question
OptiMyst Paster
Registered User
Join date: 26 Sep 2006
Posts: 8
11-12-2006 12:16
I have searched this forum and haen't found an answer yet - maybe i didn't look long enough... Anyway, when I'm buliding something I sometimes know I want to rotate a prim 90° on the Y axis. So I go to the Rotation fields in the edit menu and type in 90 for Y. Sometimes it works, mostly not. I have noticed that X and Z will change to some other number and totally flip my prim some undesired number. The best way I found was to hold Ctrl to get the rotation sphere, manually rotate it to about wehre I want, then enter 90 in Y.

Is this a bug in SL? If so, I would hazard a guess it's on the low priority list.

Optimyst Paster
Noah's Ark Construction Project
Strife Onizuka
Moonchild
Join date: 3 Mar 2004
Posts: 5,887
11-12-2006 12:40
You are experiencing gimbal lock.

It would be better to just drop a script in the prim to rotate it.

One script rotates by the global y axis, the other by the objects local y axis. Which is which i don't remember.
CODE

defualt
{
    state_entry(){llSetRot(llGetRot() * <0.0, 0.7071067, 0.0, 0.7071067>);}
}

CODE

defualt
{
    state_entry(){llSetRot(<0.0, 0.7071067, 0.0, 0.7071067> * llGetRot());}
}
_____________________
Truth is a river that is always splitting up into arms that reunite. Islanded between the arms, the inhabitants argue for a lifetime as to which is the main river.
- Cyril Connolly

Without the political will to find common ground, the continual friction of tactic and counter tactic, only creates suspicion and hatred and vengeance, and perpetuates the cycle of violence.
- James Nachtwey
OptiMyst Paster
Registered User
Join date: 26 Sep 2006
Posts: 8
11-12-2006 13:24
Hmmm, seems complicated when I have near 100 prims in a staionary building. It's more a minor inconvenience as I have learned to manually rotate the prims for coarse adjustment, then fine tune with the edit menu.

I still don't understand why gimble lock would be an issue when editing a prim - I could see it when you're writing a script to move prims around for moving objects, but not for stationary objects.
Strife Onizuka
Moonchild
Join date: 3 Mar 2004
Posts: 5,887
11-12-2006 13:39
Gimbal lock is a flaw in Euler rotations. The edit interface in SL uses Eulers but underneath it uses Quaternions (which are not susceptible to gimbal lock). The reason the numbers jump is because the interface is translating back and forth between Eulers & Quaternions.
_____________________
Truth is a river that is always splitting up into arms that reunite. Islanded between the arms, the inhabitants argue for a lifetime as to which is the main river.
- Cyril Connolly

Without the political will to find common ground, the continual friction of tactic and counter tactic, only creates suspicion and hatred and vengeance, and perpetuates the cycle of violence.
- James Nachtwey