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71 lines
2.0 KiB
71 lines
2.0 KiB
class RepulsionSolver {
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constructor(body, physicsBody, options) {
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this.body = body;
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this.physicsBody = physicsBody;
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this.setOptions(options);
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}
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setOptions(options) {
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this.options = options;
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}
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/**
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* Calculate the forces the nodes apply on each other based on a repulsion field.
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* This field is linearly approximated.
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*
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* @private
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*/
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solve() {
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var dx, dy, distance, fx, fy, repulsingForce, node1, node2;
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var nodes = this.body.nodes;
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var nodeIndices = this.physicsBody.physicsNodeIndices;
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var forces = this.physicsBody.forces;
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// repulsing forces between nodes
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var nodeDistance = this.options.nodeDistance;
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// approximation constants
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var a = (-2 / 3) / nodeDistance;
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var b = 4 / 3;
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// we loop from i over all but the last entree in the array
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// j loops from i+1 to the last. This way we do not double count any of the indices, nor i === j
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for (let i = 0; i < nodeIndices.length - 1; i++) {
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node1 = nodes[nodeIndices[i]];
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for (let j = i + 1; j < nodeIndices.length; j++) {
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node2 = nodes[nodeIndices[j]];
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dx = node2.x - node1.x;
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dy = node2.y - node1.y;
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distance = Math.sqrt(dx * dx + dy * dy);
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// same condition as BarnesHutSolver, making sure nodes are never 100% overlapping.
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if (distance === 0) {
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distance = 0.1*Math.random();
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dx = distance;
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}
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if (distance < 2 * nodeDistance) {
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if (distance < 0.5 * nodeDistance) {
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repulsingForce = 1.0;
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}
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else {
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repulsingForce = a * distance + b; // linear approx of 1 / (1 + Math.exp((distance / nodeDistance - 1) * steepness))
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}
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repulsingForce = repulsingForce / distance;
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fx = dx * repulsingForce;
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fy = dy * repulsingForce;
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forces[node1.id].x -= fx;
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forces[node1.id].y -= fy;
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forces[node2.id].x += fx;
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forces[node2.id].y += fy;
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}
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}
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}
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}
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}
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export default RepulsionSolver;
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