Ricki Moore - 1 year ago 60

Javascript Question

Im trying to achieve a gravity like simulation where all points created on the canvas will return back to the origin(0,0)/or center of canvas from random generated spots on the canvas. Like stars sucked into black hole. How can i increment or decrement the x and y values so as they reach the destination at the same point? Now im adding or subtracting 1 (i also tried to decrement the bigger number slower) but im getting the x and y off so that it looks like the point hits a wall then drops or rises to the singularity.

Example:

`var point = {`

x: 615,

y: 215,

radius: 2

}

var singularity = {

x: 751,

y: 401,

radius: 2

}

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Answer Source

Here's something I wrote for simple vector operations:

```
function vector(x, y) {
this.x = x;
this.y = y;
var point = this;
this.toString = function toString() {
return point.x + "," + point.y;
}
this.add = function (pos) {
var x = point.x + pos.x;
var y = point.y + pos.y;
return new vector(x, y);
}
this.subtract = function (pos) {
var x = point.x - pos.x;
var y = point.y - pos.y;
return new vector(x, y);
}
this.multiply = function multiply(scalar) {
var x = point.x * scalar;
var y = point.y * scalar;
return new vector(x, y);
}
this.magnitude = function magnitude() {
return Math.sqrt(Math.pow(point.x, 2) + Math.pow(point.y, 2));
}
this.unit = function unit() {
var mag = point.magnitude();
if (mag === 0)
return point;
return point.multiply(1 / mag);
}
this.angle = function angle() {
return Math.atan2(y, x);
}
}
```

You can use this to calculate the distance, direction and angle to the singularity;

```
var itemPosition = new vector(point.x, pointy);
var singularityPosition = new vector(singularity.x, singularity.y);
var displacementVector = singularityPosition.subtract(itemPosition);
var distanceFromSingluarity = displacementVector.magnitude();
var directionToSingularity = displacementVector.unit();
```

There might be some typos in there but it should get you started. Use the directionToSingularity.multiply(myCurrentSpeed) method in the vector object. It will give you a number you can add() to your pointVector to determine it's new location.

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