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.bindEventListeners(); } bindEventListeners() { 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();}); this.body.emitter.on('destroy', () => { this.stopSimulation(false); this.body.emitter.off(); }); } /** * 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', {}, false); 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 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) { this.stopSimulation(); } } /** * trigger the stabilized event. * @private */ _emitStabilized() { if (this.stabilizationIterations > 1) { setTimeout(() => { this.body.emitter.emit('stabilized', {iterations: this.stabilizationIterations}); this.stabilizationIterations = 0; }, 0); } } /** * A single simulation step (or 'tick') in the physics simulation * * @private */ physicsTick() { 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(); } 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 */ 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(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; 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 timestap 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 * @private */ 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() { 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; } } export default PhysicsEngine;