# llRot2Left

*LSL function*

```lsl
vector vector llRot2Left(rotation q);
```

- `rotation q`: Rotation to convert.

- Returns: `vector`
- Energy: 10

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](https://wiki.secondlife.com/wiki/vector) that is the left vector defined by **q**, i.e. a unit vector pointing in the local positive Y direction

```lsl title="How to use" frame="terminal"
vector result = llRot2Left(ZERO_ROTATION);
```

## Specification

Mathematically equivalent to:

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

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

```lsl
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

<details open>
<summary>Example 1</summary>

```lsl
// 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 );
    }
}
```

</details>

## Notes

Can be useful to identify the orientation of the local [sagittal-plane](https://en.wikipedia.org/wiki/sagittal_plane) of the prim, since it's y-axis is always perpendicular to this local sagittal-plane.

## See also

### Functions

- [llRot2Up](/functions/llRot2Up/)
- [llRot2Fwd](/functions/llRot2Fwd/)
- [llRot2Axis](/functions/llRot2Axis/)
- [llRot2Angle](/functions/llRot2Angle/)

---

*Source: [LlRot2Left](https://wiki.secondlife.com/wiki/LlRot2Left) on the Second Life Wiki. Content from the Second Life Wiki article LlRot2Left (revision 1194481, 2015-01-22), CC BY-SA 3.0.*

---

From lsl.dev: https://lsl.dev/functions/llRot2Left/