Difference between revisions of "LlRotLookAt"

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{{LSL_Function
{{LSL_Function
|inject-2={{Issues/SVC-1903}}
{{LSL Function/damping|damping}}
{{LSL Function/strength|strength}}
{{LSL Function/rotation|target_direction|region=*}}
|func_id=127|func_sleep=0.0|func_energy=10.0
|func_id=127|func_sleep=0.0|func_energy=10.0
|func=llRotLookAt|p1_type=rotation|p1_name=target|p2_type=float|p2_name=strength|p3_type=float|p3_name=damping
|func=llRotLookAt
|func_footnote
|p1_type=rotation|p1_name=target_direction
|func_desc=Cause object name to point its forward axis towards '''target'''
|p2_type=float|p2_name=strength
|p3_type=float|p3_name=damping
|func_footnote=To change the position in the same manner, use [[llMoveToTarget]].  For physical objects a range between .2 and 1 is good for both parameters.
|func_desc=Causes an object to smoothly rotate to {{LSLP|target_direction}} with {{LSLP|strength}} resistance at {{LSLP|damping}} force.
 
Maintains rotation {{LSLP|target_direction}} until stopped with [[llStopLookAt]].
|return_text
|return_text
|spec
|spec
|caveats
|caveats=
* In Non-Physical objects this function operates effectively the same as [[llSetLocalRot]].
* {{LSLP|damping}} seems to be capped at 1.0; greater values are reduced to 1.0 ''(Tested 21 October 2010 on server version 10.10.18.212360)''
* The minimum value for {{LSLP|strength}} seems to be 0.0445 for the function to have any effect.
|constants
|constants
|examples
|examples=
|helpers
==== Point the prim's positive y axis (''<0.0, 1.0, 0.0>'') towards a position on the sim ====
|also_functions
<source lang="lsl2">
//-- where vPosTarget is the global position of the object you want to "look" at
llRotLookAt( llRotBetween( <0.0,1.0,0.0>, llVecNorm( vPosTarget - llGetPos() ) ), 1.0, 0.4 ); // Point +Y axis towards vPosTarget
</source>
* '''vPosTarget - llGetPos()''' converts the global coordinates of the objects, to a local distance and direction from the object pointing
* Per [[llRotBetween]] article:
** '''llRotBetween''' returns a scaled rotation, unless both inputs are equal magnitude (e.g. unit vector).
** The use of [[llVecNorm]] reduces the magnitude to 1 (so that both are equal magnitude), preventing errors.
 
==== Constraining the Rotation to One Axis ====
<source lang="lsl2">
      vector detected = llDetectedPos( 0 );
      vector pos = llGetPos();
      llRotLookAt( llRotBetween( <0.0, 1.0, 0.0>, llVecNorm( <detected.x, detected.y, pos.z> - pos ) ), 1.0, 0.4 );
</source>
|helpers=
* If you want a (mostly) smooth ''constant'' (rather than damped) rate of motion in a non-physical object try this
<source lang="lsl2">
//-- Rotates Object to vRotTarget at vFltRate (in radians per second
//-- vFltRate < ~0.00000003rad/sec, (~0.00002deg/sec) will result in errors (and is just too slow anyway)
//-- vFltRate >= (PI * 5.0)rad/sec, (900deg/sec) will result in a single snap move to vRotTarget
uSteppedRotLookAt( rotation vRotTarget, float vFltRate ){
if ((integer)(vFltRate = (llAngleBetween( llGetLocalRot(), vRotTarget ) / (vFltRate / 5.0)))){
rotation vRotStep = llAxisAngle2Rot( llRot2Axis( vRotTarget / llGetLocalRot() ),
                    (1.0 / vFltRate) * llRot2Angle( vRotTarget / llGetLocalRot() ) );
vFltRate = (integer)vFltRate;
do{
llSetLocalRot( vRotStep * llGetLocalRot() );
}while (--vFltRate);
}
llSetLocalRot( vRotTarget );
} //-- for fixed time on any rotation try llSetKeyframedMotion
</source>
|also_functions=
{{LSL DefineRow||[[llLookAt]]}}
{{LSL DefineRow||[[llStopLookAt]]}}
{{LSL DefineRow||[[llSetPhysicsMaterial]]}}
{{LSL DefineRow||[[llSetKeyframedMotion]]}}
|also_events
|also_events
|also_tests
|also_tests
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|sort=RotLookAt
|sort=RotLookAt
|cat1=Physics
|cat1=Physics
|cat2=Damping
|cat2=Target
|cat3
|cat3=Rotation
|cat4
|cat4
}}
}}

Latest revision as of 16:17, 26 March 2020

Summary

Function: llRotLookAt( rotation target_direction, float strength, float damping );
0.0 Forced Delay
10.0 Energy

Causes an object to smoothly rotate to target_direction with strength resistance at damping force.

Maintains rotation target_direction until stopped with llStopLookAt.

• rotation target_direction
• float strength
• float damping seconds to critically damp in

To change the position in the same manner, use llMoveToTarget. For physical objects a range between .2 and 1 is good for both parameters.

Caveats

  • In Non-Physical objects this function operates effectively the same as llSetLocalRot.
  • damping seems to be capped at 1.0; greater values are reduced to 1.0 (Tested 21 October 2010 on server version 10.10.18.212360)
  • The minimum value for strength seems to be 0.0445 for the function to have any effect.

Examples

Point the prim's positive y axis (<0.0, 1.0, 0.0>) towards a position on the sim

//-- where vPosTarget is the global position of the object you want to "look" at
llRotLookAt( llRotBetween( <0.0,1.0,0.0>, llVecNorm( vPosTarget - llGetPos() ) ), 1.0, 0.4 ); // Point +Y axis towards vPosTarget
  • vPosTarget - llGetPos() converts the global coordinates of the objects, to a local distance and direction from the object pointing
  • Per llRotBetween article:
    • llRotBetween returns a scaled rotation, unless both inputs are equal magnitude (e.g. unit vector).
    • The use of llVecNorm reduces the magnitude to 1 (so that both are equal magnitude), preventing errors.

Constraining the Rotation to One Axis

      vector detected = llDetectedPos( 0 );
      vector pos = llGetPos();
      llRotLookAt( llRotBetween( <0.0, 1.0, 0.0>, llVecNorm( <detected.x, detected.y, pos.z> - pos ) ), 1.0, 0.4 );

Useful Snippets

  • If you want a (mostly) smooth constant (rather than damped) rate of motion in a non-physical object try this
//-- Rotates Object to vRotTarget at vFltRate (in radians per second
//-- vFltRate < ~0.00000003rad/sec, (~0.00002deg/sec) will result in errors (and is just too slow anyway)
//-- vFltRate >= (PI * 5.0)rad/sec, (900deg/sec) will result in a single snap move to vRotTarget
uSteppedRotLookAt( rotation vRotTarget, float vFltRate ){
	if ((integer)(vFltRate = (llAngleBetween( llGetLocalRot(), vRotTarget ) / (vFltRate / 5.0)))){
		rotation vRotStep = llAxisAngle2Rot( llRot2Axis( vRotTarget / llGetLocalRot() ),
		                    (1.0 / vFltRate) * llRot2Angle( vRotTarget / llGetLocalRot() ) );
		vFltRate = (integer)vFltRate;
		do{
			llSetLocalRot( vRotStep * llGetLocalRot() );
		}while (--vFltRate);
	}
	llSetLocalRot( vRotTarget );
} //-- for fixed time on any rotation try llSetKeyframedMotion

See Also

Deep Notes

Signature

function void llRotLookAt( rotation target_direction, float strength, float damping );