[JASS] Maths and Jass

[Yixx]

Hello people,,

I have had a few questions for a long time, and i have tried to find the answer, but no succes, so i am asking you guys here,,
If i want the angle between 2 point, i need a function,,
I checked the AngleBetweenPoints() function, which just used the Atan2() function,,
But what does Atan2 do? Ya, it calculates angle between 2 points, but how?
I though Atan was from ArcTangent, but why do we have Atan() and Atan2() then?
Then i heard it had something to do with polar coordinates, which involve (r,θ) (r = distance, θ = angle)
So i thought maybe Atan() calculates the 'r' (distance) and Atan2() the 'θ' (angle),, but then i still dont know why they called it Atan, if it calculates the distance, because the distance could be easily calculated with Pytagoras' function,,

So: What ar Atan() and Atan2() for,,
Also, if i want the angle between 2 point, cant i just use this:
set Angle = Acos((GetUnitX(Caster) - GetUnitX(Target))/Distance) * bj_RADTODEG

as well as:
set Angle = Asin((GetUnitY(Caster) - GetUnitY(Target))/Distance) * bj_RADTODEG

Arent these two doing the same as Atan2() ??
(I made them out of the calculation NewX = X + Dist * Cos(a) and NewY = Y + Dist * Sin(a))

Someone please help!

-Yixx,,-

 

[Teelo]

http://en.wikipedia.org/wiki/Atan2

For any real arguments x and y not both equal to zero, atan2(y, x) is the angle in radians between the positive x-axis of a plane and the point given by the coordinates (x, y) on it. The angle is positive for counter-clockwise angles (upper half-plane, y > 0), and negative for clockwise angles (lower half-plane, y < 0).

 

[Yixx]

Ok, but what does Atan do then?
And about the polar coordinates, do Atan() and Atan2() calculate the coordinates?
If so, why does PolarProjectionBJ() not use Atan() and Atan2() instead of Cos() and Sin(),,

 

[Reaper2008]

Wish i could help, greek here though so i don't even know what this means.

 

[The Reborn Devil]

I think this is how it works:
Atan2(y, x) = 2*Atan(y/(SquareRoot(x*x+y*y)+x))

But I'm not 100% sure.

 

[Teelo]

http://en.wikipedia.org/wiki/Inverse_trigonometric_functions

In mathematics, the inverse trigonometric functions or cyclometric functions are the so-called inverse functions of the trigonometric functions,

In computer programming languages the functions arcsin, arccos, arctan, are usually called asin, acos, atan.

 

[Saia_Djinn]

Atan just takes a x argument only so its not able to calculate angles through

 

[Squiggy]

Here's how you use Atan and Atan2. Say you have a vertical displacement y, and a horizontal displacement x, then the angle of elevation formed by a right triangle with those sides would be Atan(y/x) or Atan2(y, x). Now, the problem with Atan is that if x == 0, then you have a division by 0. The second problem, is what if both y and x are negative values? Atan, in that case, has no way to determine if the angle is in the top right corner of a unit circle, o
The point is that Atan2 will give you the correct angle, always. Atan will give you values between 0 and pi I believe (not too sure about this) because of sign conflicts, whereas Atan2 can give you values from 0 to 2pi.

I'll just leave this here..

 

[PurplePoot]

Almost correct, but Atan2 actually gives values between -π and π.

Atan just takes a x argument only so its not able to calculate angles through

Someone wasn't paying attention in math class...

 

[Yixx]

thanks! ^^,, i think i get it now,,
But then,, why does Atan2 give between -pi and pi, if radians go from -2pi to 2pi? (right?)

 

[The Reborn Devil]

Doesn't Atan2 give values from 0 to 2pi?
At least it goes up to 2pi.

 

[PurplePoot]

No.

The correct angle in all cases (if you are limited to 0-2π) is (Atan2(y,x)+π). Otherwise it doesn't really matter, as π+n is equal to -π+n on a circle.