Checking Collision Lots of Objects JS

Question

I've been working with an array allShapes. This array consists of objects with the same kinds of properties, like each object has a .x value, and a .y value.

Each shape has a "radius", so the detection can be easily done. For each object, the radius is exactly the same. It equals 10.

How can I effeciently make a function that checks if one shape is colliding with another? Thanks in advance!

var allShapes = [{70,30},{40,90},{287,245}];
// allShapes[0].x = 70
// For each object, there is a .x and .y value

You will need to make a double loop and check each with each other — yBrodsky
– yBrodsky, Commented Apr 27, 2017 at 14:43
@yBrodsky I would appreciate syntax, then I can accept your answer — Assafi Cohen-Arazi
– Assafi Cohen-Arazi, Commented Apr 27, 2017 at 15:02

hansmaad · Accepted Answer · 2017-04-27 14:45:15Z

2

If the naive O(n^2) solution (testing each object with all others) is not efficient enough, choose one of the well known space partitioning algorithms. There are kd-trees, octrees, quadtrees, BSP-trees etc. Maybe you should start with a simple grid. Devide your domain into cells and order your objects by cells. For a given candidate, test with all objects in the same and all adjacent cells.

answered Apr 27, 2017 at 14:45

hansmaad

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Assafi Cohen-Arazi · Accepted Answer · 2017-04-27 19:12:48Z

1

var allShapes = [{70,30},{40,90},{287,245}];

for(let i = 0; i < allShapes.length - 1; i++) {
  for(let j = i + 1; j < allShapes.length; j++) {
    //check if allShapes[i] and allShapes[j] are colliding
  }
}

Breakdown of detection:

- allShapes[i] = {70,30}
  - allShapes[j] = {40,90} => check collision
  - allShapes[j] = {287,245} => check collision
- allShapes[i] = {40,90}
  - allShapes[j] = {287,245} => check collision

edited Apr 27, 2017 at 19:12

Assafi Cohen-Arazi

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answered Apr 27, 2017 at 15:15

yBrodsky

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