LlRot2Up

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Summary

Function: vector llRot2Up( rotation q );

Computes the orientation of the local z-axis relative to the parent (i.e. the root prim or the world).
Returns a vector that is the up vector defined by q, i.e. a unit vector pointing in the positive Z direction

• rotation q

Specification

Mathematically equivalent to:

ret = llVecNorm(<0., 0., 1.> * q);

If q is known to be a unit quaternion then it can be simplified as:

ret = <0., 0., 1.> * q;

Keep in mind that object and agent rotations will always be unit quaternions. For example, <0.0, 0.0, 1.0>*llGetRot() is about 25-30% faster than llRot2Up(llGetRot()) depending on the VM used. If done often and at extremely fast rates, it can be advantageous to even save <0.0, 0.0, 1.0> to a local/global variable and reuse it.

Examples

// Move a prim 5 metres forwards along its own z 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 = llRot2Up( llGetLocalRot() );
        llSetPos( llGetLocalPos() + v * 5 );
    }
}

Notes

Can be useful to identify the orientation of the local horizontal-plane of the prim, since it's z-axis is always perpendicular to this local horizontal plane.

See Also

Functions

•  llRot2Left
•  llRot2Fwd
•  llRot2Axis
•  llRot2Angle

Deep Notes

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Signature

function vector llRot2Up( rotation q );