Whatizit?

astar-path is a Javascript library that computes a ballistic flight path between a start and goal nodes. The trajectory computed is subject to position, velocity, and acceleration constraints as well as optional user defined node constraints.

PathNode

Trajectories are defined by a PathNode array. Each PathNode has position, velocity and acceleration vectors (i.e., s,v,a). Here we define start and goal nodes of a desired trajectory. Both start and goal nodes have zero velocity and acceleration:

var start = new PathNode([200,-299,0]); // x,y,z position
var goal = new PathNode([-200,299,0]); // x,y,z position

PathFactory

Trajectories are created by a PathFactory. Here we create a three dimensional PathFactory that forbids x or y axis movement below a zcruise height of 15 and also forbids z-movement below zero:

var zcruise = 15;
var pf = new PathFactory({
    dimensions: 3,
    maxVelocity: [25,25,4], // x,y,z velocity
    maxAcceleration: [5,5,1], // x,y,z acceleration
    maxIterations: 5000,
    isConstrained: (node) => node.s[2] < zcruise,
    constrain: (n) => {
        if (n.s[2] < 0) {
            return null; // only paths above bed
        }
        if (n.s[2] < zcruise) {
            if (n.v[0] || n.v[1] || n.a[0] || n.a[1]) {
                return null; // no xy movement below zcruise;
            }
        }
        return n;
    },
});

PathFactory

Given a start and goal PathNode, you can quickly create a trajectory by calling the findPath method:

var result = pf.findPath(start,goal);

Here is a typical trajectory computed by findPath in under 20ms:

Installation

npm install astar-path