llRot2Left
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Summary
Function: vector llRot2Left( rotation q );| 19 | Function ID |
| 0.0 | Forced Delay |
| 10.0 | Energy |
Computes the orientation of the local y-axis relative to the parent (i.e. relative to the root prim or the world).
Returns a vector that is the left vector defined by q, i.e. a unit vector pointing in the local positive Y direction
| • rotation | q |
Specification
Mathematically equivalent to:
ret = llVecNorm(<0., 1., 0.> * q);
If q is known to be a unit quaternion then it can be simplified as:
ret = <0., 1., 0.> * q;
Keep in mind that object and agent rotations will always be unit quaternions. For example, <0.0, 1.0, 0.0>*llGetRot() is about 25-30% faster than llRot2Left(llGetRot()) depending on the VM used. If done often and at extremely fast rates, it can be advantageous to even save <0.0, 1.0, 0.0> to a local/global variable and reuse it.
Caveats
Examples
// Move an object 5 metres forwards along its own y axis, when touched, no matter how the object is oriented in world.
// Works for a root or child prim
default
{
touch_start(integer total_number)
{
vector v = llRot2Left( llGetLocalRot() );
llSetPos( llGetLocalPos() + v * 5 );
}
}
Notes
Can be useful to identify the orientation of the local 
sagittal-plane of the prim, since it's y-axis is always perpendicular to this local sagittal-plane.
See Also
Functions
| • | llRot2Up | |||
| • | llRot2Fwd | |||
| • | llRot2Axis | |||
| • | llRot2Angle |