Circle maths, i guess

[>@tack!<]

How to get a random location within a circle? i tried some stuff but they werent perfectly distrubuted in the circle ( particles ) like i once had shown in a video.

[JackGriffin]

q = Rnd() * (PI * 2)
r = Sqrt(Rnd())
x = (radius * r) * Cos(q)
y = (radius * r) * Sin(q)

[anth]

Isn't this basic maths? Either way, if the middle of the circle is at (x=0, y=0) and the circle has a radius of r then this would give you a random location within the circle:

Code: Select all

function GetRandomLocation(float radius, out float x_loc, out float y_loc)
{
    local float angle, distance;

    angle = RandRange(0.0, 2 * PI);
    distance = RandRange(0.0, radius);

    x_loc = Cos(angle) * distance;
    y_loc = Sin(angle) * distance;
}


[>@tack!<]

Yes i tried this one too and its maybe perfect enough BUT think like this: if radius is VERY LONG and say the difference between 2 angles is minimum 0.000001 rad. Then at large radii you'll get empty spaces between 2 angles or am I wrong? But I may have an idea that works if not I'll just use this because i won't use large radii.

Edit: sec I might misread your posts ill read it on my laptop when I wake up lol xd
Edit2: hm no i read it the way i meant to. however i dont get JackGriffin's r = Sqrt(Rnd()) part.
Edit3: using r = Sqrt(Rnd()) made a better circle than without. Can i maybe have an explanation why r = Sqrt(Rnd()) is needed?
Edit4: nvm i get it , secret edit 5: no i dont

[JackGriffin]

It's there to add uniformity to the frequency of points. The disparity between q and r is high at a low Rnd() value but approaches equality as you progress towards Rnd() being 1 (the center). It's actually hard to not get results that congregate more to the center, isn't it?

Thank Ferali, he hit me with "Oh you need a perihelical check" once in replying to a question I had. I ended up having to order a book from Amazon to understand what the hell he meant.

[>@tack!<]

ah yes i get it thanks and ferali too :p

[Feralidragon]

Trigonometry... I advice you to study it, the basics aren't that difficult at all, and once you domain at least the basics, this and other math problems in mod making become quite easy to solve with simple plain math, as long they have angles and vectors into the mix.