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Function: float llAtan2( float y, float x );

Returns a float that is the arctangent2 of y, x.

• float y
• float x

Similar to the arctangent(y/x) except it utilizes the signs of x & y to determine the quadrant and avoids division by zero.


If x is zero and...

  • y is zero, zero is returned.
  • y is positive, PI/2 is returned.
  • y is negative, -PI/2 is returned.

Or ((y > 0) - (y < 0)) * PI_BY_TWO.
The returned value is in the range [-PI, PI][1].


<lsl>default {

   float num1 = llFrand(100.0);
   float num2 = llFrand(100.0);
   llOwnerSay("y = " + (string)num1);
   llOwnerSay("x = " + (string)num2);
   llOwnerSay("The arctangent of y divided by x is " + (string)llAtan2(num1, num2));

}</lsl><lsl>//Function with input of a vector determining the position of a target and returning //a string with the literal compass-direction of that target towards your position //by Ramana Sweetwater 2009/01, any use allowed license :-) //corrected by Patrick Muggins

string compass (vector target) {

   vector source = llGetPos();
   list DIRS =["W","NW","N","NE","E","SE","S","SW","W"];
   integer index = llCeil(3.5 - (4 * llAtan2(target.y - source.y, target.x - source.x) / PI));
   return llList2String(DIRS, index);


/Compass QA

See Also


• llSin llAsin sine & inverse Sine
• llCos llAcos cosine & inverse cosine
• llTan tangent


•  Wikipedia:Atan2
•  Wikipedia:Inverse trigonometric function

Deep Notes

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  1. ^ The ranges in this article are written in Interval Notation.


function float llAtan2( float y, float x );