LlRot2Left

Wiki description

Computes the orientation of the local y-axis relative to the parent (i.e. relative to the root prim or the world).

Return value notes

Returns a vector that is the left vector defined by q, i.e. a unit vector pointing in the local positive Y direction

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.

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.