vis.js is a dynamic, browser-based visualization library
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/**
* Created by Alex on 2/23/2015.
*/
class RepulsionSolver {
constructor(body, physicsBody, options) {
this.body = body;
this.physicsBody = physicsBody;
this.setOptions(options);
}
setOptions(options) {
this.options = options;
}
/**
* Calculate the forces the nodes apply on each other based on a repulsion field.
* This field is linearly approximated.
*
* @private
*/
solve() {
var dx, dy, distance, fx, fy, repulsingForce, node1, node2;
var nodes = this.body.nodes;
var nodeIndices = this.physicsBody.physicsNodeIndices;
var forces = this.physicsBody.forces;
// repulsing forces between nodes
var nodeDistance = this.options.nodeDistance;
// approximation constants
var a = (-2 / 3) / nodeDistance;
var b = 4 / 3;
// we loop from i over all but the last entree in the array
// j loops from i+1 to the last. This way we do not double count any of the indices, nor i == j
for (let i = 0; i < nodeIndices.length - 1; i++) {
node1 = nodes[nodeIndices[i]];
for (let j = i + 1; j < nodeIndices.length; j++) {
node2 = nodes[nodeIndices[j]];
dx = node2.x - node1.x;
dy = node2.y - node1.y;
distance = Math.sqrt(dx * dx + dy * dy);
// same condition as BarnesHutSolver, making sure nodes are never 100% overlapping.
if (distance == 0) {
distance = 0.1*Math.random();
dx = distance;
}
if (distance < 2 * nodeDistance) {
if (distance < 0.5 * nodeDistance) {
repulsingForce = 1.0;
}
else {
repulsingForce = a * distance + b; // linear approx of 1 / (1 + Math.exp((distance / nodeDistance - 1) * steepness))
}
repulsingForce = repulsingForce / distance;
fx = dx * repulsingForce;
fy = dy * repulsingForce;
forces[node1.id].x -= fx;
forces[node1.id].y -= fy;
forces[node2.id].x += fx;
forces[node2.id].y += fy;
}
}
}
}
}
export default RepulsionSolver;