Difference between revisions of "LlAtan2"

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//a string with the literal compass-direction of that target towards your position
 
//a string with the literal compass-direction of that target towards your position
 
//by Ramana Sweetwater 2009/01, any use allowed license :-)
 
//by Ramana Sweetwater 2009/01, any use allowed license :-)
 +
//corrected by Patrick Muggins
  
 
string compass (vector target)  
 
string compass (vector target)  
{//-1.2732395447351 == -8/TWO_PI
+
{
     if(target -= llGetPos())//Have we arrived?
+
     vector source = llGetPos();
     {//We have not arrived.
+
     list DIRS =["W","NW","N","NE","E","SE","S","SW","W"];
        list DIRS = [ "E", "SE", "S", "SW", "W", "NW", "N", "NE" ];
+
    return llList2String(DIRS,llCeil(3.5-((4*llAtan2((target.y-source.y),(target.x-source.x)))/PI)));
        integer index = llRound((llAtan2(target.y, target.x) * -1.2732395447351)) % 8;
+
        return llList2String(DIRS, index);
+
    }
+
    return "X";//we have arrived! X marks the spot.
+
 
}</lsl>
 
}</lsl>
 
[[/Compass QA]]
 
[[/Compass QA]]

Revision as of 02:06, 27 November 2010

Summary

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. Returns zero if x and y are zero.
The returned value is in the range [-PI, PI][1].

Examples

<lsl>default {

 state_entry()
 {
   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"];
   return llList2String(DIRS,llCeil(3.5-((4*llAtan2((target.y-source.y),(target.x-source.x)))/PI)));

}</lsl>

/Compass QA

See Also

Functions

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

Articles

•  Wikipedia:Atan2
•  Wikipedia:Inverse_trigonometric_function

Deep Notes

Search JIRA for related Issues

Footnotes

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

Signature

function float llAtan2( float y, float x );