How to find angle

[schme16]

I appologise for what could be a really silly question, but I havn't found an answer that made sense to me, yet.

What I'm after is how to find the angle (in degrees or radians) between two co-ordinate points

eg: what is the angle between x1,y1 and x2,y2

any and all help greatly appreciated!

Cheers,

[bmelts]

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

Conveniently located in Lua's math library.

[BlackBulletIV]

I took this code from FlashPunk:

Code: Select all

function math.angle(x1, y1, x2, y2)
    local a = math.deg(math.atan2(y2 - y1, x2 - x1))
    if a < 0 then
        return a + 360
    else
        return a
    end
end

[schme16]

Thanks heaps guys, sorry I fail at math so hard

[bartbes]

I prefer radians, as, well, all functions are using radians, so degrees are only useful when you are outputting it, also, if you replace the if by the modulus operator you get this:

Code: Select all

function math.angle(x1, y1, x2, y2)
    return math.deg(math.atan2(y2-y1, x2-x1))%360
end

Which is.. perhaps a bit nicer. On yet another note, I dislike putting your own functions in the std libs, but I guess, as most of the things I mentioned, it's a matter of preference.

[BlackBulletIV]

Code: Select all

function math.angle(x1, y1, x2, y2)
    return math.deg(math.atan2(y2-y1, x2-x1))%360
end

Wow, that's really clever. Modulo is a pretty awesome operator.

[schme16]

heck yes it is, thanks heaps bartbes