Question

I want to detect if one canvas object for example – circle crosses another canvas object

For example I have 2 circles moving

I am using paper.js library

    c1 = new Path.Circle([20, 20], 20);
    c1.fillColor = 'red';

    c2 = c1.clone();
    c2.position += 500;
    c2.fillColor = 'green';

    c = 0;

    function onFrame(event){
        c += 0.1;
        c1.position += c;
        c2.position -= c;
    }

I want to detect when c1 hits c2

Answer 1

In your onFrame method, you want to check whether the distance between the centers of the circles is less than twice the radius. If true, then you have a collision.