Difference between revisions of "LlAtan2"

From Second Life Wiki
Jump to: navigation, search
(spacing)
m
Line 5: Line 5:
 
|p2_type=float|p2_name=x|p2_desc
 
|p2_type=float|p2_name=x|p2_desc
 
|return_type=float
 
|return_type=float
|return_text=that is the {{wikipedia|Atan2|arctangent2}} of '''y''', '''x'''.
+
|return_text=that is the {{wikipedia|Atan2|arctangent2}} of {{LSLP|y}}, {{LSLP|x}}.
|func_footnote=Similar to the <span class="plainlinks">{{wikipedia|Inverse_trigonometric_functions|arctangent}}</span>('''y'''/'''x''') except it utilizes the signs of '''x''' & '''y''' to determine the quadrant and avoids  division by zero. Returns zero if '''x''' and '''y''' are zero, returns '''PI/2''' if '''x''' is zero and '''y'''  is positive, returns '''-PI/2''' if '''x''' is zero and '''y''' is negative.<br />
+
|func_footnote=Similar to the <span class="plainlinks">{{wikipedia|Inverse_trigonometric_functions|arctangent}}</span>({{LSLP|y}}/{{LSLP|x}}) except it utilizes the signs of {{LSLP|x}} & {{LSLP|y}} to determine the quadrant and avoids  division by zero. <br />
 +
If {{LSLP|x}} is zero and...
 +
* {{LSLP|y}} is zero, '''zero''' is returned.
 +
* {{LSLP|y}} is positive, '''PI/2''' is returned.
 +
* {{LSLP|y}} is negative, '''-PI/2''' is returned.
 +
Or <code>(({{LSL Param|y}} > 0) - ({{LSL Param|y}} < 0)) * [[PI_BY_TWO]]</code>
 
The returned value is in the range {{Interval|gte=-[[PI]]|gteh=-PI|lte=PI|center=return}}{{Interval/Footnote}}.
 
The returned value is in the range {{Interval|gte=-[[PI]]|gteh=-PI|lte=PI|center=return}}{{Interval/Footnote}}.
 
|spec
 
|spec

Revision as of 21:12, 6 June 2012

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 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].

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

}</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 );