atan2: Difference between revisions

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|gr1= Math - Geometry
|gr1= Math - Geometry


|descr= [[Image:atan.jpg|right|200px]] ArcTangent of ''y/x''. Used to determine the angle of a vector ''[x,y]''. Result in [[Number#Degrees|Degrees]] between -180 and 180.
|descr= [[File:atan.jpg|right|300px]] ArcTangent of ''y/x''. Used to determine the angle of a vector ''[y,x]''. Result in [[Number#Degrees|Degrees]] between -180 and 180.
{{Feature | Informative | This command can handle ''x'' being 0, unlike when using [[atan]], and will return 90 }}
{{Feature|informative|This command can handle ''x'' being 0, unlike when using [[atan]], and will return 90}}
{{Feature | important | Even though this command is a binary operator just like [[select]] command, it has [[SQF Syntax#Rules_of_Precedence | higher precedence]] than [[select]] command, therefore the following expression: <br>{{hl|_pos select 0 [[atan2]] (_pos select 1)}}<br> will produce an error. The correct usage in this case will be: <br>{{hl|(_pos select 0) [[atan2]] (_pos select 1)}}}}
{{Feature|important|
This command has [[SQF Syntax#Rules of Precedence|higher precedence]] than the [[select]] command, therefore beware of the case below:
<sqf notrim>
_pos select 0 atan2 (_pos select 1) // error
(_pos select 0) atan2 (_pos select 1) // OK
</sqf>
 
Alternatively, consider using the [[a hash b|#]] operator: <sqf inline>_pos # 0 atan2 _pos # 1</sqf>
}}


|s1= y [[atan2]] x
|s1= y [[atan2]] x
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|r1= [[Number]]
|r1= [[Number]]


|x1= <code>_xy = [5,3];
|x1= <sqf>
_degrees = (_xy select 0) atan2 (_xy select 1); // 59.0362</code>
_yx = [5,3];
_degrees = (_yx select 0) atan2 (_yx select 1); // 59.0362
</sqf>


|x2= Get direction from _obj1 to _obj2:
|x2= Get direction from _obj1 to _obj2:
<code>_vd = getPosASL _obj2 vectorDiff getPosASL _obj1;
<sqf>
_dir = (_vd [[select]] 0) [[atan2]] (_vd [[select]] 1); // _dir range from -180 to +180
_vd = getPosASL _obj2 vectorDiff getPosASL _obj1;
_dir = (_dir + 360) % 360; // _dir range from 0 to 360</code>
_dir = (_vd select 0) atan2 (_vd select 1); // _dir range from -180 to +180
_dir = (_dir + 360) % 360; // _dir range from 0 to 360
</sqf>


|x3= Get relative direction from _obj1 to _obj2:
|x3= Get relative direction from _obj1 to _obj2:
<code>_xy = _obj1 worldToModel getPosASL _obj2;
<sqf>
_dir = (_xy [[select]] 0) [[atan2]] (_xy [[select]] 1); // _dir range from -180 to +180
_yx = _obj1 worldToModel getPosASL _obj2;
_dir = (_dir + 360) % 360; // _dir range from 0 to 360</code>
_dir = (_yx select 0) atan2 (_yx select 1); // _dir range from -180 to +180
_dir = (_dir + 360) % 360; // _dir range from 0 to 360
</sqf>


|seealso= [[atan]] [[tan]] [[sin]] [[cos]] [[asin]] [[acos]] [[rad]] [[pi]] [[vectorCos]] [[getPos]] [[getRelPos]] [[Math Commands]]
|seealso= [[atan]] [[tan]] [[sin]] [[cos]] [[asin]] [[acos]] [[rad]] [[pi]] [[vectorCos]] [[BIS_fnc_dirTo]] [[getRelPos]] [[getRelDir]]
}}
}}
<dl class="command_description">
<dt></dt>
<dd class="notedate">Posted on 08:00, 18 November 2009</dd>
<dt class="note">[[User:KeV|KeV]]</dt>
<dd class="note">
To get the direction of an object from the player:
<code>_dir = ((getPos _obj select 0) - (getPos player select 0)) atan2 ((getPos _obj [[select]] 1) - ([[getPos]] [[player]] [[select]] 1));
//_dir will be from -180 to 180.
</code>
If positive values are needed then use:
<code>if (_dir < 0) then {_dir = _dir + 360};
</code>
Or just use [[BIS_fnc_dirTo]] directly.
</dl>

Latest revision as of 09:38, 25 March 2024

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Hover & click on the images for description

Description

Description:
atan.jpg
ArcTangent of y/x. Used to determine the angle of a vector [y,x]. Result in Degrees between -180 and 180.
ⓘ
This command can handle x being 0, unlike when using atan, and will return 90
⚠
This command has higher precedence than the select command, therefore beware of the case below:

_pos select 0 atan2 (_pos select 1) // error (_pos select 0) atan2 (_pos select 1) // OK

Alternatively, consider using the # operator: _pos # 0 atan2 _pos # 1
Groups:
Math - Geometry

Syntax

Syntax:
y atan2 x
Parameters:
y: Number
x: Number
Return Value:
Number

Examples

Example 1:
_yx = [5,3]; _degrees = (_yx select 0) atan2 (_yx select 1); // 59.0362
Example 2:
Get direction from _obj1 to _obj2:
_vd = getPosASL _obj2 vectorDiff getPosASL _obj1; _dir = (_vd select 0) atan2 (_vd select 1); // _dir range from -180 to +180 _dir = (_dir + 360) % 360; // _dir range from 0 to 360
Example 3:
Get relative direction from _obj1 to _obj2:
_yx = _obj1 worldToModel getPosASL _obj2; _dir = (_yx select 0) atan2 (_yx select 1); // _dir range from -180 to +180 _dir = (_dir + 360) % 360; // _dir range from 0 to 360

Additional Information

See also:
atan tan sin cos asin acos rad pi vectorCos BIS_fnc_dirTo getRelPos getRelDir

Notes

Report bugs on the Feedback Tracker and/or discuss them on the Arma Discord or on the Forums.
Only post proven facts here! Add Note
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