Euclidean distance to calculate if something is near something

currently i have using a framework and it 开发者_开发技巧has a function called distance2D, and it has this description:

Calculate the Euclidean distance between two points (considering a point as a vector object). Disregards the Z component of the vectors and is thus a little faster.

and this is how i use it

if(g.getCenterPointGlobal().distance2D(target.getCenterPointGlobal()) > 1)
   System.out.println("Near");

i have totally no idea what a Euclidean distance is, i am thinking that it can be used to calculate how far 2 points are? because i am trying to compare distance between 2 objects and if they are near within a certain range i want to do something. how would i be able to use this?

Euclidean distance is the distance between 2 points as if you were using a ruler. I don't know what are the dimensions of your Euclidean space, but be careful because the function you are using just takes in consideration the first two dimensions (x,y). Thus if you have a space with 3 dimensions(x,y,z) it will only use the first two(x,y of x,y,z) to calculate the distance. This may give a wrong result.

For what I understood, if you want to trigger some action when two points are within some range you should make:

<!-- language: lang-java -->
if(g.getCenterPointGlobal().distance2D(target.getCenterPointGlobal()) < RANGE)          
    System.out.println("Near");

The Euclidean distance is calculated tracing a straight line between two points and measuring as the hypotenuse of a imaginary isosceles triangle between the two lines and a complementary point. This measure is scalar, so it's a good metric for your calculations.

Euclidean geometry is a coordinate system in which space is flat, not curved. You don't need to care about non-Euclidean geometry unless for example you're dealing with coordinates mapped onto a sphere, such as calculating the shortest travel distance between two places on Earth.

I imagine this function will basically use Pythagoras' theorem to calculate the distance between the two objects. However, as the description says, it disregards the Z component. In otherwords, it will only give a correct answer if both points have the same Z value (aka "depth").

If you wish to compare distances and save time, use not the distance itself, but its square: (x1-x2)^2 + (y1-y2)^2. Don't take sqrt. So, your distances will work exactly as euclidian ones, but quickly.