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';
import ForceAtlas2BasedRepulsionSolver from './components/physics/FA2BasedRepulsionSolver';
import ForceAtlas2BasedCentralGravitySolver from './components/physics/FA2BasedCentralGravitySolver';
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.referenceState = {};
this.freezeCache = {};
this.renderTimer = undefined;
// parameters for the adaptive timestep
this.adaptiveTimestep = false;
this.adaptiveTimestepEnabled = false;
this.adaptiveCounter = 0;
this.adaptiveInterval = 3;
this.stabilized = false;
this.startedStabilization = false;
this.stabilizationIterations = 0;
this.ready = false; // will be set to true if the stabilize
// default options
this.options = {};
this.defaultOptions = {
enabled: true,
barnesHut: {
theta: 0.5,
gravitationalConstant: -2000,
centralGravity: 0.3,
springLength: 95,
springConstant: 0.04,
damping: 0.09,
avoidOverlap: 0
},
forceAtlas2Based: {
theta: 0.5,
gravitationalConstant: -50,
centralGravity: 0.01,
springConstant: 0.08,
springLength: 100,
damping: 0.4,
avoidOverlap: 0
},
repulsion: {
centralGravity: 0.2,
springLength: 200,
springConstant: 0.05,
nodeDistance: 100,
damping: 0.09,
avoidOverlap: 0
},
hierarchicalRepulsion: {
centralGravity: 0.0,
springLength: 100,
springConstant: 0.01,
nodeDistance: 120,
damping: 0.09
},
maxVelocity: 50,
minVelocity: 0.75, // px/s
solver: 'barnesHut',
stabilization: {
enabled: true,
iterations: 1000, // maximum number of iteration to stabilize
updateInterval: 50,
onlyDynamicEdges: false,
fit: true
},
timestep: 0.5,
adaptiveTimestep: true
};
util.extend(this.options, this.defaultOptions);
this.timestep = 0.5;
this.layoutFailed = false;
this.bindEventListeners();
}
bindEventListeners() {
this.body.emitter.on('initPhysics', () => {this.initPhysics();});
this.body.emitter.on('_layoutFailed', () => {this.layoutFailed = true;});
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();});
this.body.emitter.on('destroy', () => {
this.stopSimulation(false);
this.body.emitter.off();
});
// this event will trigger a rebuilding of the cache everything. Used when nodes or edges have been added or removed.
this.body.emitter.on("_dataChanged", () => {
// update shortcut lists
this.updatePhysicsData();
});
// debug: show forces
// this.body.emitter.on("afterDrawing", (ctx) => {this._drawForces(ctx);});
}
/**
* set the physics options
* @param options
*/
setOptions(options) {
if (options !== undefined) {
if (options === false) {
this.options.enabled = false;
this.physicsEnabled = false;
this.stopSimulation();
}
else {
this.physicsEnabled = true;
util.selectiveNotDeepExtend(['stabilization'], this.options, options);
util.mergeOptions(this.options, options, 'stabilization');
if (options.enabled === undefined) {
this.options.enabled = true;
}
if (this.options.enabled === false) {
this.physicsEnabled = false;
this.stopSimulation();
}
// set the timestep
this.timestep = this.options.timestep;
}
}
this.init();
}
/**
* configure the engine.
*/
init() {
var options;
if (this.options.solver === 'forceAtlas2Based') {
options = this.options.forceAtlas2Based;
this.nodesSolver = new ForceAtlas2BasedRepulsionSolver(this.body, this.physicsBody, options);
this.edgesSolver = new SpringSolver(this.body, this.physicsBody, options);
this.gravitySolver = new ForceAtlas2BasedCentralGravitySolver(this.body, this.physicsBody, options);
}
else 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);
this.gravitySolver = new CentralGravitySolver(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);
this.gravitySolver = new CentralGravitySolver(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;
}
/**
* initialize the engine
*/
initPhysics() {
if (this.physicsEnabled === true && this.options.enabled === true) {
if (this.options.stabilization.enabled === true) {
this.stabilize();
}
else {
this.stabilized = false;
this.ready = true;
this.body.emitter.emit('fit', {}, this.layoutFailed); // if the layout failed, we use the approximation for the zoom
this.startSimulation();
}
}
else {
this.ready = true;
this.body.emitter.emit('fit');
}
}
/**
* Start the simulation
*/
startSimulation() {
if (this.physicsEnabled === true && this.options.enabled === true) {
this.stabilized = false;
// when visible, adaptivity is disabled.
this.adaptiveTimestep = false;
// this sets the width of all nodes initially which could be required for the avoidOverlap
this.body.emitter.emit("_resizeNodes");
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(emit = true) {
this.stabilized = true;
if (emit === true) {
this._emitStabilized();
}
if (this.viewFunction !== undefined) {
this.body.emitter.off('initRedraw', this.viewFunction);
this.viewFunction = undefined;
if (emit === true) {
this.body.emitter.emit('_stopRendering');
}
}
}
/**
* The viewFunction inserts this step into each render loop. 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) {
this.stopSimulation();
}
}
/**
* trigger the stabilized event.
* @private
*/
_emitStabilized(amountOfIterations = this.stabilizationIterations) {
if (this.stabilizationIterations > 1 || this.startedStabilization === true) {
setTimeout(() => {
this.body.emitter.emit('stabilized', {iterations: amountOfIterations});
this.startedStabilization = false;
this.stabilizationIterations = 0;
}, 0);
}
}
/**
* A single simulation step (or 'tick') in the physics simulation
*
* @private
*/
physicsTick() {
// 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;
}
if (this.stabilized === false) {
// adaptivity means the timestep adapts to the situation, only applicable for stabilization
if (this.adaptiveTimestep === true && this.adaptiveTimestepEnabled === true) {
// this is the factor for increasing the timestep on success.
let factor = 1.2;
// we assume the adaptive interval is
if (this.adaptiveCounter % this.adaptiveInterval === 0) { // we leave the timestep stable for "interval" iterations.
// first the big step and revert. Revert saves the reference state.
this.timestep = 2 * this.timestep;
this.calculateForces();
this.moveNodes();
this.revert();
// now the normal step. Since this is the last step, it is the more stable one and we will take this.
this.timestep = 0.5 * this.timestep;
// since it's half the step, we do it twice.
this.calculateForces();
this.moveNodes();
this.calculateForces();
this.moveNodes();
// we compare the two steps. if it is acceptable we double the step.
if (this._evaluateStepQuality() === true) {
this.timestep = factor * this.timestep;
}
else {
// if not, we decrease the step to a minimum of the options timestep.
// if the decreased timestep is smaller than the options step, we do not reset the counter
// we assume that the options timestep is stable enough.
if (this.timestep/factor < this.options.timestep) {
this.timestep = this.options.timestep;
}
else {
// if the timestep was larger than 2 times the option one we check the adaptivity again to ensure
// that large instabilities do not form.
this.adaptiveCounter = -1; // check again next iteration
this.timestep = Math.max(this.options.timestep, this.timestep/factor);
}
}
}
else {
// normal step, keeping timestep constant
this.calculateForces();
this.moveNodes();
}
// increment the counter
this.adaptiveCounter += 1;
}
else {
// case for the static timestep, we reset it to the one in options and take a normal step.
this.timestep = this.options.timestep;
this.calculateForces();
this.moveNodes();
}
// determine if the network has stabilzied
if (this.stabilized === true) {
this.revert();
}
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
*/
updatePhysicsData() {
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(nodes[nodeId].id);
}
}
}
// get edge indices for physics
for (let edgeId in edges) {
if (edges.hasOwnProperty(edgeId)) {
if (edges[edgeId].options.physics === true) {
this.physicsBody.physicsEdgeIndices.push(edges[edgeId].id);
}
}
}
// 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;
this.referenceState = {};
for (let i = 0; i < nodeIds.length; i++) {
let nodeId = nodeIds[i];
if (nodes[nodeId] !== undefined) {
if (nodes[nodeId].options.physics === true) {
this.referenceState[nodeId] = {
positions: {x:nodes[nodeId].x, y:nodes[nodeId].y}
};
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];
}
}
}
/**
* This compares the reference state to the current state
*/
_evaluateStepQuality() {
let dx, dy, dpos;
let nodes = this.body.nodes;
let reference = this.referenceState;
let posThreshold = 0.3;
for (let nodeId in this.referenceState) {
if (this.referenceState.hasOwnProperty(nodeId) && nodes[nodeId] !== undefined) {
dx = nodes[nodeId].x - reference[nodeId].positions.x;
dy = nodes[nodeId].y - reference[nodeId].positions.y;
dpos = Math.sqrt(Math.pow(dx,2) + Math.pow(dy,2))
if (dpos > posThreshold) {
return false;
}
}
}
return true;
}
/**
* move the nodes one timestep and check if they are stabilized
* @returns {boolean}
*/
moveNodes() {
var nodeIndices = this.physicsBody.physicsNodeIndices;
var maxVelocity = this.options.maxVelocity ? this.options.maxVelocity : 1e9;
var maxNodeVelocity = 0;
var averageNodeVelocity = 0;
// the velocity threshold (energy in the system) for the adaptivity toggle
var velocityAdaptiveThreshold = 5;
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
maxNodeVelocity = Math.max(maxNodeVelocity,nodeVelocity);
averageNodeVelocity += nodeVelocity;
}
// evaluating the stabilized and adaptiveTimestepEnabled conditions
this.adaptiveTimestepEnabled = (averageNodeVelocity/nodeIndices.length) < velocityAdaptiveThreshold;
this.stabilized = maxNodeVelocity < this.options.minVelocity;
}
/**
* Perform the actual step
*
* @param nodeId
* @param maxVelocity
* @returns {number}
* @private
*/
_performStep(nodeId,maxVelocity) {
let node = this.body.nodes[nodeId];
let timestep = this.timestep;
let forces = this.physicsBody.forces;
let 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;
}
let 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
*/
stabilize(iterations = this.options.stabilization.iterations) {
if (typeof iterations !== 'number') {
console.log('The stabilize method needs a numeric amount of iterations. Switching to default: ', this.options.stabilization.iterations);
iterations = this.options.stabilization.iterations;
}
if (this.physicsBody.physicsNodeIndices.length === 0) {
this.ready = true;
return;
}
// enable adaptive timesteps
this.adaptiveTimestep = true && this.options.adaptiveTimestep;
// this sets the width of all nodes initially which could be required for the avoidOverlap
this.body.emitter.emit("_resizeNodes");
// stop the render loop
this.stopSimulation();
// set stabilze to false
this.stabilized = false;
// block redraw requests
this.body.emitter.emit('_blockRedraw');
this.targetIterations = iterations;
// start the stabilization
if (this.options.stabilization.onlyDynamicEdges === true) {
this._freezeNodes();
}
this.stabilizationIterations = 0;
setTimeout(() => this._stabilizationBatch(),0);
}
/**
* One batch of stabilization
* @private
*/
_stabilizationBatch() {
// this is here to ensure that there is at least one start event.
if (this.startedStabilization === false) {
this.body.emitter.emit('startStabilizing');
this.startedStabilization = true;
}
var count = 0;
while (this.stabilized === false && count < this.options.stabilization.updateInterval && this.stabilizationIterations < this.targetIterations) {
this.physicsTick();
count++;
}
if (this.stabilized === false && this.stabilizationIterations < this.targetIterations) {
this.body.emitter.emit('stabilizationProgress', {iterations: this.stabilizationIterations, total: this.targetIterations});
setTimeout(this._stabilizationBatch.bind(this),0);
}
else {
this._finalizeStabilization();
}
}
/**
* Wrap up the stabilization, fit and emit the events.
* @private
*/
_finalizeStabilization() {
this.body.emitter.emit('_allowRedraw');
if (this.options.stabilization.fit === true) {
this.body.emitter.emit('fit');
}
if (this.options.stabilization.onlyDynamicEdges === true) {
this._restoreFrozenNodes();
}
this.body.emitter.emit('stabilizationIterationsDone');
this.body.emitter.emit('_requestRedraw');
if (this.stabilized === true) {
this._emitStabilized();
}
else {
this.startSimulation();
}
this.ready = true;
}
_drawForces(ctx) {
for (var i = 0; i < this.physicsBody.physicsNodeIndices.length; i++) {
let node = this.body.nodes[this.physicsBody.physicsNodeIndices[i]];
let force = this.physicsBody.forces[this.physicsBody.physicsNodeIndices[i]];
let factor = 20;
let colorFactor = 0.03;
let forceSize = Math.sqrt(Math.pow(force.x,2) + Math.pow(force.x,2));
let size = Math.min(Math.max(5,forceSize),15);
let arrowSize = 3*size;
let color = util.HSVToHex((180 - Math.min(1,Math.max(0,colorFactor*forceSize))*180) / 360,1,1);
ctx.lineWidth = size;
ctx.strokeStyle = color;
ctx.beginPath();
ctx.moveTo(node.x,node.y);
ctx.lineTo(node.x+factor*force.x, node.y+factor*force.y);
ctx.stroke();
let angle = Math.atan2(force.y, force.x);
ctx.fillStyle = color;
ctx.arrow(node.x + factor*force.x + Math.cos(angle)*arrowSize, node.y + factor*force.y+Math.sin(angle)*arrowSize, angle, arrowSize);
ctx.fill();
}
}
}
export default PhysicsEngine;