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255 lines
9.4 KiB
255 lines
9.4 KiB
import BarnesHutSolver from './components/physics/BarnesHutSolver';
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import Repulsion from './components/physics/RepulsionSolver';
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import HierarchicalRepulsion from './components/physics/HierarchicalRepulsionSolver';
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import SpringSolver from './components/physics/SpringSolver';
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import HierarchicalSpringSolver from './components/physics/HierarchicalSpringSolver';
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import CentralGravitySolver from './components/physics/CentralGravitySolver';
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import ForceAtlas2BasedRepulsionSolver from './components/physics/FA2BasedRepulsionSolver';
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import ForceAtlas2BasedCentralGravitySolver from './components/physics/FA2BasedCentralGravitySolver';
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class PhysicsBase {
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constructor() {
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this.physicsBody = {physicsNodeIndices:[], physicsEdgeIndices:[], forces: {}, velocities: {}};
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this.options = {};
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this.referenceState = {};
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this.previousStates = {};
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this.startedStabilization = false;
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this.stabilized = false;
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this.stabilizationIterations = 0;
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this.timestep = 0.5;
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}
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/**
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* configure the engine.
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*/
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initPhysicsSolvers() {
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var options;
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if (this.options.solver === 'forceAtlas2Based') {
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options = this.options.forceAtlas2Based;
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this.nodesSolver = new ForceAtlas2BasedRepulsionSolver(this.body, this.physicsBody, options);
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this.edgesSolver = new SpringSolver(this.body, this.physicsBody, options);
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this.gravitySolver = new ForceAtlas2BasedCentralGravitySolver(this.body, this.physicsBody, options);
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}
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else if (this.options.solver === 'repulsion') {
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options = this.options.repulsion;
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this.nodesSolver = new Repulsion(this.body, this.physicsBody, options);
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this.edgesSolver = new SpringSolver(this.body, this.physicsBody, options);
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this.gravitySolver = new CentralGravitySolver(this.body, this.physicsBody, options);
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}
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else if (this.options.solver === 'hierarchicalRepulsion') {
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options = this.options.hierarchicalRepulsion;
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this.nodesSolver = new HierarchicalRepulsion(this.body, this.physicsBody, options);
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this.edgesSolver = new HierarchicalSpringSolver(this.body, this.physicsBody, options);
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this.gravitySolver = new CentralGravitySolver(this.body, this.physicsBody, options);
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}
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else { // barnesHut
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options = this.options.barnesHut;
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this.nodesSolver = new BarnesHutSolver(this.body, this.physicsBody, options);
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this.edgesSolver = new SpringSolver(this.body, this.physicsBody, options);
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this.gravitySolver = new CentralGravitySolver(this.body, this.physicsBody, options);
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}
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this.modelOptions = options;
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}
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/**
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* A single simulation step (or 'tick') in the physics simulation
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*
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* @private
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*/
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physicsTick() {
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// this is here to ensure that there is no start event when the network is already stable.
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if (this.startedStabilization === false) {
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this.emit('startStabilizing');
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this.startedStabilization = true;
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}
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if (this.stabilized === false) {
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// adaptivity means the timestep adapts to the situation, only applicable for stabilization
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if (this.adaptiveTimestep === true && this.adaptiveTimestepEnabled === true) {
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// this is the factor for increasing the timestep on success.
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let factor = 1.2;
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// we assume the adaptive interval is
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if (this.adaptiveCounter % this.adaptiveInterval === 0) { // we leave the timestep stable for "interval" iterations.
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// first the big step and revert. Revert saves the reference state.
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this.timestep = 2 * this.timestep;
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this.calculateForces();
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this.moveNodes();
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this.revert();
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// now the normal step. Since this is the last step, it is the more stable one and we will take this.
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this.timestep = 0.5 * this.timestep;
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// since it's half the step, we do it twice.
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this.calculateForces();
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this.moveNodes();
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this.calculateForces();
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this.moveNodes();
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// we compare the two steps. if it is acceptable we double the step.
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if (this._evaluateStepQuality() === true) {
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this.timestep = factor * this.timestep;
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}
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else {
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// if not, we decrease the step to a minimum of the options timestep.
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// if the decreased timestep is smaller than the options step, we do not reset the counter
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// we assume that the options timestep is stable enough.
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if (this.timestep/factor < this.options.timestep) {
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this.timestep = this.options.timestep;
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}
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else {
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// if the timestep was larger than 2 times the option one we check the adaptivity again to ensure
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// that large instabilities do not form.
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this.adaptiveCounter = -1; // check again next iteration
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this.timestep = Math.max(this.options.timestep, this.timestep/factor);
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}
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}
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}
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else {
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// normal step, keeping timestep constant
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this.calculateForces();
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this.moveNodes();
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}
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// increment the counter
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this.adaptiveCounter += 1;
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}
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else {
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// case for the static timestep, we reset it to the one in options and take a normal step.
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this.timestep = this.options.timestep;
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this.calculateForces();
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this.moveNodes();
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}
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// determine if the network has stabilzied
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if (this.stabilized === true) {
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this.revert();
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}
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this.stabilizationIterations++;
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}
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}
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/**
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* Revert the simulation one step. This is done so after stabilization, every new start of the simulation will also say stabilized.
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*/
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revert() {
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var nodeIds = Object.keys(this.previousStates);
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var nodes = this.body.nodes;
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var velocities = this.physicsBody.velocities;
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this.referenceState = {};
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for (let i = 0; i < nodeIds.length; i++) {
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let nodeId = nodeIds[i];
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if (nodes[nodeId] !== undefined) {
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if (this.isWorker || nodes[nodeId].options.physics === true) {
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this.referenceState[nodeId] = {
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positions: {x:nodes[nodeId].x, y:nodes[nodeId].y}
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};
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velocities[nodeId].x = this.previousStates[nodeId].vx;
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velocities[nodeId].y = this.previousStates[nodeId].vy;
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nodes[nodeId].x = this.previousStates[nodeId].x;
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nodes[nodeId].y = this.previousStates[nodeId].y;
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}
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}
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else {
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delete this.previousStates[nodeId];
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}
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}
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}
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/**
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* This compares the reference state to the current state
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*/
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_evaluateStepQuality() {
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let dx, dy, dpos;
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let nodes = this.body.nodes;
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let reference = this.referenceState;
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let posThreshold = 0.3;
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for (let nodeId in this.referenceState) {
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if (this.referenceState.hasOwnProperty(nodeId) && nodes[nodeId] !== undefined) {
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dx = nodes[nodeId].x - reference[nodeId].positions.x;
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dy = nodes[nodeId].y - reference[nodeId].positions.y;
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dpos = Math.sqrt(Math.pow(dx,2) + Math.pow(dy,2))
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if (dpos > posThreshold) {
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return false;
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}
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}
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}
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return true;
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}
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/**
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* move the nodes one timestap and check if they are stabilized
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* @returns {boolean}
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*/
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moveNodes() {
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var nodeIndices = this.physicsBody.physicsNodeIndices;
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var maxVelocity = this.options.maxVelocity ? this.options.maxVelocity : 1e9;
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var maxNodeVelocity = 0;
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var averageNodeVelocity = 0;
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// the velocity threshold (energy in the system) for the adaptivity toggle
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var velocityAdaptiveThreshold = 5;
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for (let i = 0; i < nodeIndices.length; i++) {
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let nodeId = nodeIndices[i];
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let nodeVelocity = this._performStep(nodeId, maxVelocity);
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// stabilized is true if stabilized is true and velocity is smaller than vmin --> all nodes must be stabilized
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maxNodeVelocity = Math.max(maxNodeVelocity,nodeVelocity);
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averageNodeVelocity += nodeVelocity;
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}
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// evaluating the stabilized and adaptiveTimestepEnabled conditions
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this.adaptiveTimestepEnabled = (averageNodeVelocity/nodeIndices.length) < velocityAdaptiveThreshold;
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this.stabilized = maxNodeVelocity < this.options.minVelocity;
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}
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// TODO consider moving _performStep in here
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// right now Physics nodes don't have setX setY functions
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// - maybe switch logic of setX and set x?
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// - add functions to physics nodes - seems not desirable
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/**
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* calculate the forces for one physics iteration.
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*/
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calculateForces() {
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this.gravitySolver.solve();
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this.nodesSolver.solve();
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this.edgesSolver.solve();
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}
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/**
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* One batch of stabilization
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* @private
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*/
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_stabilizationBatch() {
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// this is here to ensure that there is at least one start event.
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if (this.startedStabilization === false) {
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this.emit('startStabilizing');
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this.startedStabilization = true;
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}
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var count = 0;
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while (this.stabilized === false && count < this.options.stabilization.updateInterval && this.stabilizationIterations < this.targetIterations) {
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this.physicsTick();
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count++;
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}
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if (this.stabilized === false && this.stabilizationIterations < this.targetIterations) {
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this.emit('stabilizationProgress', {iterations: this.stabilizationIterations, total: this.targetIterations});
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setTimeout(this._stabilizationBatch.bind(this),0);
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}
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else {
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this._finalizeStabilization();
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}
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}
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}
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export default PhysicsBase;
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