vis.js is a dynamic, browser-based visualization library
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class HierarchicalSpringSolver {
constructor(body, physicsBody, options) {
this.body = body;
this.physicsBody = physicsBody;
this.setOptions(options);
}
setOptions(options) {
this.options = options;
}
/**
* This function calculates the springforces on the nodes, accounting for the support nodes.
*
* @private
*/
solve() {
var edgeLength, edge;
var dx, dy, fx, fy, springForce, distance;
var edges = this.body.edges;
var factor = 0.5;
var edgeIndices = this.physicsBody.physicsEdgeIndices;
var nodeIndices = this.physicsBody.physicsNodeIndices;
var forces = this.physicsBody.forces;
// initialize the spring force counters
for (let i = 0; i < nodeIndices.length; i++) {
let nodeId = nodeIndices[i];
forces[nodeId].springFx = 0;
forces[nodeId].springFy = 0;
}
// forces caused by the edges, modelled as springs
for (let i = 0; i < edgeIndices.length; i++) {
edge = edges[edgeIndices[i]];
if (edge.connected === true) {
edgeLength = edge.options.length === undefined ? this.options.springLength : edge.options.length;
dx = (edge.from.x - edge.to.x);
dy = (edge.from.y - edge.to.y);
distance = Math.sqrt(dx * dx + dy * dy);
distance = distance === 0 ? 0.01 : distance;
// the 1/distance is so the fx and fy can be calculated without sine or cosine.
springForce = this.options.springConstant * (edgeLength - distance) / distance;
fx = dx * springForce;
fy = dy * springForce;
if (edge.to.level != edge.from.level) {
forces[edge.toId].springFx -= fx;
forces[edge.toId].springFy -= fy;
forces[edge.fromId].springFx += fx;
forces[edge.fromId].springFy += fy;
}
else {
forces[edge.toId].x -= factor*fx;
forces[edge.toId].y -= factor*fy;
forces[edge.fromId].x += factor*fx;
forces[edge.fromId].y += factor*fy;
}
}
}
// normalize spring forces
var springForce = 1;
var springFx, springFy;
for (let i = 0; i < nodeIndices.length; i++) {
let nodeId = nodeIndices[i];
springFx = Math.min(springForce,Math.max(-springForce,forces[nodeId].springFx));
springFy = Math.min(springForce,Math.max(-springForce,forces[nodeId].springFy));
forces[nodeId].x += springFx;
forces[nodeId].y += springFy;
}
// retain energy balance
var totalFx = 0;
var totalFy = 0;
for (let i = 0; i < nodeIndices.length; i++) {
let nodeId = nodeIndices[i];
totalFx += forces[nodeId].x;
totalFy += forces[nodeId].y;
}
var correctionFx = totalFx / nodeIndices.length;
var correctionFy = totalFy / nodeIndices.length;
for (let i = 0; i < nodeIndices.length; i++) {
let nodeId = nodeIndices[i];
forces[nodeId].x -= correctionFx;
forces[nodeId].y -= correctionFy;
}
}
}
export default HierarchicalSpringSolver;