LSL Wiki : ExamplePointChildAtTarget

This function, when called in a child prim of an object, will point the chosen axis of the child prim towards a target location specified in region-coordinates; a demonstration of how, if you wish to relate a child prim's rotation to the global axes, you need to unrotate your result by the root prim's rotation.

In this example, it is using a repeating sensor to point the child prim's x-axis at the nearest avatar.

-- Cross Lament

// PointChildAtTarget - points child's 'axis' towards region-coordinate 'pos'.
PointChildAtTarget( vector pos, vector axis )
{
    // The global position of the child prim.
    vector mypos = llGetPos() ;
    
    // The unit vector towards the target.
    vector targetvector = llVecNorm( pos - mypos ) ;
    
    // Find the rotation required to point the unrotated (ie. world) axis
    // towards the target, then unrotate this by the root prim's rotation.
    rotation targetrot = llRotBetween( axis, targetvector ) / llGetRootRotation() ;
    
    llSetLocalRot( targetrot ) ;
}

// The axis of the child prim you wish to point at the target object.
vector desiredaxis = < 1, 0, 0 > ;

default
{
    state_entry()
    {
        llSensorRepeat( "", NULL_KEY, AGENT, 10, PI, 1 ) ;
    }
    
    sensor( integer num )
    {
        PointChildAtTarget( llDetectedPos( 0 ), desiredaxis ) ;
    }
}

Examples