vis.js is a dynamic, browser-based visualization library
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import BarnesHutSolver from './components/physics/BarnesHutSolver';
import Repulsion from './components/physics/RepulsionSolver';
import HierarchicalRepulsion from './components/physics/HierarchicalRepulsionSolver';
import SpringSolver from './components/physics/SpringSolver';
import HierarchicalSpringSolver from './components/physics/HierarchicalSpringSolver';
import CentralGravitySolver from './components/physics/CentralGravitySolver';
var util = require('../../util');
class PhysicsEngine {
constructor(body) {
this.body = body;
this.physicsBody = {physicsNodeIndices:[], physicsEdgeIndices:[], forces: {}, velocities: {}};
this.physicsEnabled = true;
this.simulationInterval = 1000 / 60;
this.requiresTimeout = true;
this.previousStates = {};
this.freezeCache = {};
this.renderTimer = undefined;
this.stabilized = false;
this.stabilizationIterations = 0;
this.ready = false; // will be set to true if the stabilize
// default options
this.options = {};
this.defaultOptions = {
barnesHut: {
theta: 0.5,
gravitationalConstant: -2000,
centralGravity: 0.3,
springLength: 95,
springConstant: 0.04,
damping: 0.09
},
repulsion: {
centralGravity: 0.2,
springLength: 200,
springConstant: 0.05,
nodeDistance: 100,
damping: 0.09
},
hierarchicalRepulsion: {
centralGravity: 0.0,
springLength: 100,
springConstant: 0.01,
nodeDistance: 120,
damping: 0.09
},
maxVelocity: 50,
minVelocity: 0.1, // px/s
solver: 'barnesHut',
stabilization: {
enabled: true,
iterations: 1000, // maximum number of iteration to stabilize
updateInterval: 100,
onlyDynamicEdges: false,
fit: true
},
timestep: 0.5
}
util.extend(this.options, this.defaultOptions);
this.body.emitter.on('initPhysics', () => {this.initPhysics();});
this.body.emitter.on('resetPhysics', () => {this.stopSimulation(); this.ready = false;});
this.body.emitter.on('disablePhysics', () => {this.physicsEnabled = false; this.stopSimulation();});
this.body.emitter.on('restorePhysics', () => {
this.setOptions(this.options);
if (this.ready === true) {
this.startSimulation();
}
});
this.body.emitter.on('startSimulation', () => {
if (this.ready === true) {
this.startSimulation();
}
})
this.body.emitter.on('stopSimulation', () => {this.stopSimulation();});
}
setOptions(options) {
if (options === false) {
this.physicsEnabled = false;
this.stopSimulation();
}
else {
this.physicsEnabled = true;
if (options !== undefined) {
util.selectiveNotDeepExtend(['stabilization'], this.options, options);
util.mergeOptions(this.options, options, 'stabilization')
}
this.init();
}
}
init() {
var options;
if (this.options.solver === 'repulsion') {
options = this.options.repulsion;
this.nodesSolver = new Repulsion(this.body, this.physicsBody, options);
this.edgesSolver = new SpringSolver(this.body, this.physicsBody, options);
}
else if (this.options.solver === 'hierarchicalRepulsion') {
options = this.options.hierarchicalRepulsion;
this.nodesSolver = new HierarchicalRepulsion(this.body, this.physicsBody, options);
this.edgesSolver = new HierarchicalSpringSolver(this.body, this.physicsBody, options);
}
else { // barnesHut
options = this.options.barnesHut;
this.nodesSolver = new BarnesHutSolver(this.body, this.physicsBody, options);
this.edgesSolver = new SpringSolver(this.body, this.physicsBody, options);
}
this.gravitySolver = new CentralGravitySolver(this.body, this.physicsBody, options);
this.modelOptions = options;
}
initPhysics() {
if (this.physicsEnabled === true) {
if (this.options.stabilization.enabled === true) {
this.stabilize();
}
else {
this.stabilized = false;
this.ready = true;
this.body.emitter.emit('fit', {duration: 0}, true)
this.startSimulation();
}
}
else {
this.ready = true;
this.body.emitter.emit('_redraw');
}
}
/**
* Start the simulation
*/
startSimulation() {
if (this.physicsEnabled === true) {
this.stabilized = false;
if (this.viewFunction === undefined) {
this.viewFunction = this.simulationStep.bind(this);
this.body.emitter.on('initRedraw', this.viewFunction);
this.body.emitter.emit('_startRendering');
}
}
else {
this.body.emitter.emit('_redraw');
}
}
/**
* Stop the simulation, force stabilization.
*/
stopSimulation() {
this.stabilized = true;
this._emitStabilized();
if (this.viewFunction !== undefined) {
this.body.emitter.off('initRedraw', this.viewFunction);
this.viewFunction = undefined;
this.body.emitter.emit('_stopRendering');
}
}
/**
* The viewFunction inserts this step into each renderloop. It calls the physics tick and handles the cleanup at stabilized.
*
*/
simulationStep() {
// check if the physics have settled
var startTime = Date.now();
this.physicsTick();
var physicsTime = Date.now() - startTime;
// run double speed if it is a little graph
if ((physicsTime < 0.4 * this.simulationInterval || this.runDoubleSpeed === true) && this.stabilized === false) {
this.physicsTick();
// this makes sure there is no jitter. The decision is taken once to run it at double speed.
this.runDoubleSpeed = true;
}
if (this.stabilized === true) {
if (this.stabilizationIterations > 1) {
// trigger the 'stabilized' event.
// The event is triggered on the next tick, to prevent the case that
// it is fired while initializing the Network, in which case you would not
// be able to catch it
this.stabilizationIterations = 0;
this.startedStabilization = false;
this._emitStabilized();
}
else {
this.stabilizationIterations = 0;
}
this.stopSimulation();
}
}
_emitStabilized() {
if (this.stabilizationIterations > 1) {
setTimeout(() => {
this.body.emitter.emit('stabilized', {iterations: this.stabilizationIterations});
}, 0);
}
}
/**
* A single simulation step (or 'tick') in the physics simulation
*
* @private
*/
physicsTick() {
if (this.stabilized === false) {
this.calculateForces();
this.stabilized = this.moveNodes();
// determine if the network has stabilzied
if (this.stabilized === true) {
this.revert();
}
else {
// this is here to ensure that there is no start event when the network is already stable.
if (this.startedStabilization === false) {
this.body.emitter.emit('startStabilizing');
this.startedStabilization = true;
}
}
this.stabilizationIterations++;
}
}
/**
* Nodes and edges can have the physics toggles on or off. A collection of indices is created here so we can skip the check all the time.
*
* @private
*/
updatePhysicsIndices() {
this.physicsBody.forces = {};
this.physicsBody.physicsNodeIndices = [];
this.physicsBody.physicsEdgeIndices = [];
let nodes = this.body.nodes;
let edges = this.body.edges;
// get node indices for physics
for (let nodeId in nodes) {
if (nodes.hasOwnProperty(nodeId)) {
if (nodes[nodeId].options.physics === true) {
this.physicsBody.physicsNodeIndices.push(nodeId);
}
}
}
// get edge indices for physics
for (let edgeId in edges) {
if (edges.hasOwnProperty(edgeId)) {
if (edges[edgeId].options.physics === true) {
this.physicsBody.physicsEdgeIndices.push(edgeId);
}
}
}
// get the velocity and the forces vector
for (let i = 0; i < this.physicsBody.physicsNodeIndices.length; i++) {
let nodeId = this.physicsBody.physicsNodeIndices[i];
this.physicsBody.forces[nodeId] = {x:0,y:0};
// forces can be reset because they are recalculated. Velocities have to persist.
if (this.physicsBody.velocities[nodeId] === undefined) {
this.physicsBody.velocities[nodeId] = {x:0,y:0};
}
}
// clean deleted nodes from the velocity vector
for (let nodeId in this.physicsBody.velocities) {
if (nodes[nodeId] === undefined) {
delete this.physicsBody.velocities[nodeId];
}
}
}
/**
* Revert the simulation one step. This is done so after stabilization, every new start of the simulation will also say stabilized.
*/
revert() {
var nodeIds = Object.keys(this.previousStates);
var nodes = this.body.nodes;
var velocities = this.physicsBody.velocities;
for (let i = 0; i < nodeIds.length; i++) {
let nodeId = nodeIds[i];
if (nodes[nodeId] !== undefined) {
if (nodes[nodeId].options.physics === true) {
velocities[nodeId].x = this.previousStates[nodeId].vx;
velocities[nodeId].y = this.previousStates[nodeId].vy;
nodes[nodeId].x = this.previousStates[nodeId].x;
nodes[nodeId].y = this.previousStates[nodeId].y;
}
}
else {
delete this.previousStates[nodeId];
}
}
}
/**
* move the nodes one timestap and check if they are stabilized
* @returns {boolean}
*/
moveNodes() {
var nodesPresent = false;
var nodeIndices = this.physicsBody.physicsNodeIndices;
var maxVelocity = this.options.maxVelocity ? this.options.maxVelocity : 1e9;
var stabilized = true;
var vminCorrected = this.options.minVelocity / Math.max(this.body.view.scale,0.05);
for (let i = 0; i < nodeIndices.length; i++) {
let nodeId = nodeIndices[i];
let nodeVelocity = this._performStep(nodeId, maxVelocity);
// stabilized is true if stabilized is true and velocity is smaller than vmin --> all nodes must be stabilized
stabilized = nodeVelocity < vminCorrected && stabilized === true;
nodesPresent = true;
}
if (nodesPresent === true) {
if (vminCorrected > 0.5*this.options.maxVelocity) {
return false;
}
else {
return stabilized;
}
}
return true;
}
/**
* Perform the actual step
*
* @param nodeId
* @param maxVelocity
* @returns {number}
* @private
*/
_performStep(nodeId,maxVelocity) {
var node = this.body.nodes[nodeId];
var timestep = this.options.timestep;
var forces = this.physicsBody.forces;
var velocities = this.physicsBody.velocities;
// store the state so we can revert
this.previousStates[nodeId] = {x:node.x, y:node.y, vx:velocities[nodeId].x, vy:velocities[nodeId].y};
if (node.options.fixed.x === false) {
let dx = this.modelOptions.damping * velocities[nodeId].x; // damping force
let ax = (forces[nodeId].x - dx) / node.options.mass; // acceleration
velocities[nodeId].x += ax * timestep; // velocity
velocities[nodeId].x = (Math.abs(velocities[nodeId].x) > maxVelocity) ? ((velocities[nodeId].x > 0) ? maxVelocity : -maxVelocity) : velocities[nodeId].x;
node.x += velocities[nodeId].x * timestep; // position
}
else {
forces[nodeId].x = 0;
velocities[nodeId].x = 0;
}
if (node.options.fixed.y === false) {
let dy = this.modelOptions.damping * velocities[nodeId].y; // damping force
let ay = (forces[nodeId].y - dy) / node.options.mass; // acceleration
velocities[nodeId].y += ay * timestep; // velocity
velocities[nodeId].y = (Math.abs(velocities[nodeId].y) > maxVelocity) ? ((velocities[nodeId].y > 0) ? maxVelocity : -maxVelocity) : velocities[nodeId].y;
node.y += velocities[nodeId].y * timestep; // position
}
else {
forces[nodeId].y = 0;
velocities[nodeId].y = 0;
}
var totalVelocity = Math.sqrt(Math.pow(velocities[nodeId].x,2) + Math.pow(velocities[nodeId].y,2));
return totalVelocity;
}
/**
* calculate the forces for one physics iteration.
*/
calculateForces() {
this.gravitySolver.solve();
this.nodesSolver.solve();
this.edgesSolver.solve();
}
/**
* When initializing and stabilizing, we can freeze nodes with a predefined position. This greatly speeds up stabilization
* because only the supportnodes for the smoothCurves have to settle.
*
* @private
*/
_freezeNodes() {
var nodes = this.body.nodes;
for (var id in nodes) {
if (nodes.hasOwnProperty(id)) {
if (nodes[id].x && nodes[id].y) {
this.freezeCache[id] = {x:nodes[id].options.fixed.x,y:nodes[id].options.fixed.y};
nodes[id].options.fixed.x = true;
nodes[id].options.fixed.y = true;
}
}
}
}
/**
* Unfreezes the nodes that have been frozen by _freezeDefinedNodes.
*
* @private
*/
_restoreFrozenNodes() {
var nodes = this.body.nodes;
for (var id in nodes) {
if (nodes.hasOwnProperty(id)) {
if (this.freezeCache[id] !== undefined) {
nodes[id].options.fixed.x = this.freezeCache[id].x;
nodes[id].options.fixed.y = this.freezeCache[id].y;
}
}
}
this.freezeCache = {};
}
/**
* Find a stable position for all nodes
* @private
*/
stabilize() {
// stop the render loop
this.stopSimulation();
// set stabilze to false
this.stabilized = false;
// block redraw requests
this.body.emitter.emit('_blockRedrawRequests');
this.body.emitter.emit('startStabilizing');
this.startedStabilization = true;
// start the stabilization
if (this.options.stabilization.onlyDynamicEdges === true) {
this._freezeNodes();
}
this.stabilizationIterations = 0;
setTimeout(this._stabilizationBatch.bind(this),0);
}
_stabilizationBatch() {
var count = 0;
while (this.stabilized === false && count < this.options.stabilization.updateInterval && this.stabilizationIterations < this.options.stabilization.iterations) {
this.physicsTick();
this.stabilizationIterations++;
count++;
}
if (this.stabilized === false && this.stabilizationIterations < this.options.stabilization.iterations) {
this.body.emitter.emit('stabilizationProgress', {iterations: this.stabilizationIterations, total: this.options.stabilization.iterations});
setTimeout(this._stabilizationBatch.bind(this),0);
}
else {
this._finalizeStabilization();
}
}
_finalizeStabilization() {
this.body.emitter.emit('_allowRedrawRequests');
if (this.options.stabilization.fit === true) {
this.body.emitter.emit('fit', {duration:0});
}
if (this.options.stabilization.onlyDynamicEdges === true) {
this._restoreFrozenNodes();
}
this.body.emitter.emit('stabilizationIterationsDone');
this.body.emitter.emit('_requestRedraw');
this.ready = true;
}
}
export default PhysicsEngine;