vis.js is a dynamic, browser-based visualization library
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class SpringSolver {
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() {
let edgeLength, edge;
let edgeIndices = this.physicsBody.physicsEdgeIndices;
let edges = this.body.edges;
let nodes = this.body.nodes;
let node1, node2, node3;
// forces caused by the edges, modelled as springs
for (let i = 0; i < edgeIndices.length; i++) {
edge = edges[edgeIndices[i]];
if (edge.connected === true && edge.toId !== edge.fromId) {
// only calculate forces if nodes are in the same sector
if (this.body.nodes[edge.toId] !== undefined && this.body.nodes[edge.fromId] !== undefined) {
if (edge.edgeType.via !== undefined) {
edgeLength = edge.options.length === undefined ? this.options.springLength : edge.options.length;
node1 = nodes[edge.to.id];
node2 = nodes[edge.edgeType.via.id];
node3 = nodes[edge.from.id];
this._calculateSpringForce(node1, node2, 0.5 * edgeLength);
this._calculateSpringForce(node2, node3, 0.5 * edgeLength);
}
else {
// the * 1.5 is here so the edge looks as large as a smooth edge. It does not initially because the smooth edges use
// the support nodes which exert a repulsive force on the to and from nodes, making the edge appear larger.
edgeLength = edge.options.length === undefined ? this.options.springLength * 1.5: edge.options.length;
this._calculateSpringForce(nodes[edge.from.id], nodes[edge.to.id], edgeLength);
}
}
}
}
}
/**
* This is the code actually performing the calculation for the function above.
*
* @param node1
* @param node2
* @param edgeLength
* @private
*/
_calculateSpringForce(node1, node2, edgeLength) {
let dx = (node1.x - node2.x);
let dy = (node1.y - node2.y);
let distance = Math.max(Math.sqrt(dx * dx + dy * dy),0.01);
// the 1/distance is so the fx and fy can be calculated without sine or cosine.
let springForce = this.options.springConstant * (edgeLength - distance) / distance;
let fx = dx * springForce;
let fy = dy * springForce;
// handle the case where one node is not part of the physcis
if (this.physicsBody.forces[node1.id] !== undefined) {
this.physicsBody.forces[node1.id].x += fx;
this.physicsBody.forces[node1.id].y += fy;
}
if (this.physicsBody.forces[node2.id] !== undefined) {
this.physicsBody.forces[node2.id].x -= fx;
this.physicsBody.forces[node2.id].y -= fy;
}
}
}
export default SpringSolver;