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104 lines
3.0 KiB
104 lines
3.0 KiB
/**
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* Created by Alex on 2/25/2015.
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*/
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class HierarchicalSpringSolver {
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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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var edgeLength, edge, edgeId;
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var dx, dy, fx, fy, springForce, distance;
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var edges = this.body.edges;
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var nodeIndices = this.physicsBody.calculationNodeIndices;
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var forces = this.physicsBody.forces;
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// initialize the spring force counters
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for (let i = 0; i < nodeIndices.length; i++) {
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let nodeId = nodeIndices[i];
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forces[nodeId].springFx = 0;
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forces[nodeId].springFy = 0;
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}
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// forces caused by the edges, modelled as springs
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for (edgeId in edges) {
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if (edges.hasOwnProperty(edgeId)) {
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edge = edges[edgeId];
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if (edge.connected === true) {
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edgeLength = edge.properties.length === undefined ? this.options.springLength : edge.properties.length;
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dx = (edge.from.x - edge.to.x);
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dy = (edge.from.y - edge.to.y);
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distance = Math.sqrt(dx * dx + dy * dy);
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distance = distance == 0 ? 0.01 : distance;
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// the 1/distance is so the fx and fy can be calculated without sine or cosine.
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springForce = this.options.springConstant * (edgeLength - distance) / distance;
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fx = dx * springForce;
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fy = dy * springForce;
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if (edge.to.level != edge.from.level) {
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forces[edge.toId].springFx -= fx;
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forces[edge.toId].springFy -= fy;
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forces[edge.fromId].springFx += fx;
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forces[edge.fromId].springFy += fy;
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}
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else {
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let factor = 0.5;
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forces[edge.toId].x -= factor*fx;
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forces[edge.toId].y -= factor*fy;
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forces[edge.fromId].x += factor*fx;
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forces[edge.fromId].y += factor*fy;
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}
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}
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}
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}
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// normalize spring forces
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var springForce = 1;
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var springFx, springFy;
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for (let i = 0; i < nodeIndices.length; i++) {
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let nodeId = nodeIndices[i];
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springFx = Math.min(springForce,Math.max(-springForce,forces[nodeId].springFx));
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springFy = Math.min(springForce,Math.max(-springForce,forces[nodeId].springFy));
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forces[nodeId].x += springFx;
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forces[nodeId].y += springFy;
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}
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// retain energy balance
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var totalFx = 0;
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var totalFy = 0;
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for (let i = 0; i < nodeIndices.length; i++) {
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let nodeId = nodeIndices[i];
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totalFx += forces[nodeId].x;
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totalFy += forces[nodeId].y;
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}
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var correctionFx = totalFx / nodeIndices.length;
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var correctionFy = totalFy / nodeIndices.length;
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for (let i = 0; i < nodeIndices.length; i++) {
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let nodeId = nodeIndices[i];
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forces[nodeId].x -= correctionFx;
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forces[nodeId].y -= correctionFy;
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}
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}
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}
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export {HierarchicalSpringSolver};
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