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83 lines
2.8 KiB
83 lines
2.8 KiB
class SpringSolver {
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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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* This function calculates the springforces on the nodes, accounting for the support nodes.
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*
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* @private
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*/
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solve() {
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let edgeLength, edge;
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let edgeIndices = this.physicsBody.physicsEdgeIndices;
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let edges = this.body.edges;
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let nodes = this.body.nodes;
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let node1, node2, node3;
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// forces caused by the edges, modelled as springs
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for (let i = 0; i < edgeIndices.length; i++) {
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edge = edges[edgeIndices[i]];
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if (edge.connected === true && edge.toId !== edge.fromId) {
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// only calculate forces if nodes are in the same sector
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if (this.body.nodes[edge.toId] !== undefined && this.body.nodes[edge.fromId] !== undefined) {
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if (edge.edgeType.via !== undefined) {
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edgeLength = edge.options.length === undefined ? this.options.springLength : edge.options.length;
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node1 = nodes[edge.to.id];
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node2 = nodes[edge.edgeType.via.id];
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node3 = nodes[edge.from.id];
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this._calculateSpringForce(node1, node2, 0.5 * edgeLength);
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this._calculateSpringForce(node2, node3, 0.5 * edgeLength);
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}
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else {
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// the * 1.5 is here so the edge looks as large as a smooth edge. It does not initially because the smooth edges use
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// the support nodes which exert a repulsive force on the to and from nodes, making the edge appear larger.
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edgeLength = edge.options.length === undefined ? this.options.springLength * 1.5: edge.options.length;
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this._calculateSpringForce(nodes[edge.from.id], nodes[edge.to.id], edgeLength);
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}
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}
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}
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}
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}
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/**
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* This is the code actually performing the calculation for the function above.
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*
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* @param node1
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* @param node2
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* @param edgeLength
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* @private
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*/
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_calculateSpringForce(node1, node2, edgeLength) {
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let dx = (node1.x - node2.x);
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let dy = (node1.y - node2.y);
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let distance = Math.max(Math.sqrt(dx * dx + dy * dy),0.01);
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// the 1/distance is so the fx and fy can be calculated without sine or cosine.
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let springForce = this.options.springConstant * (edgeLength - distance) / distance;
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let fx = dx * springForce;
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let fy = dy * springForce;
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// handle the case where one node is not part of the physcis
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if (this.physicsBody.forces[node1.id] !== undefined) {
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this.physicsBody.forces[node1.id].x += fx;
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this.physicsBody.forces[node1.id].y += fy;
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}
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if (this.physicsBody.forces[node2.id] !== undefined) {
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this.physicsBody.forces[node2.id].x -= fx;
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this.physicsBody.forces[node2.id].y -= fy;
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}
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}
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}
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export default SpringSolver;
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