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154 lines
4.3 KiB
154 lines
4.3 KiB
/**
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* Calculate the forces the nodes apply on eachother 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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exports._calculateNodeForces = function () {
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var dx, dy, distance, fx, fy,
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repulsingForce, node1, node2, i, j;
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var nodes = this.calculationNodes;
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var nodeIndices = this.calculationNodeIndices;
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// repulsing forces between nodes
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var nodeDistance = this.constants.physics.hierarchicalRepulsion.nodeDistance;
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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 (i = 0; i < nodeIndices.length - 1; i++) {
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node1 = nodes[nodeIndices[i]];
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for (j = i + 1; j < nodeIndices.length; j++) {
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node2 = nodes[nodeIndices[j]];
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// nodes only affect nodes on their level
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if (node1.level == node2.level) {
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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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var steepness = 0.05;
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if (distance < nodeDistance) {
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repulsingForce = -Math.pow(steepness*distance,2) + Math.pow(steepness*nodeDistance,2);
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}
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else {
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repulsingForce = 0;
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}
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// normalize force with
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if (distance == 0) {
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distance = 0.01;
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}
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else {
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repulsingForce = repulsingForce / distance;
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}
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fx = dx * repulsingForce;
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fy = dy * repulsingForce;
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node1.fx -= fx;
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node1.fy -= fy;
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node2.fx += fx;
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node2.fy += 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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* this function calculates the effects of the springs in the case of unsmooth curves.
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*
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* @private
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*/
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exports._calculateHierarchicalSpringForces = function () {
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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.edges;
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var nodes = this.calculationNodes;
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var nodeIndices = this.calculationNodeIndices;
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for (var i = 0; i < nodeIndices.length; i++) {
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var node1 = nodes[nodeIndices[i]];
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node1.springFx = 0;
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node1.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) {
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// only calculate forces if nodes are in the same sector
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if (this.nodes.hasOwnProperty(edge.toId) && this.nodes.hasOwnProperty(edge.fromId)) {
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edgeLength = edge.physics.springLength;
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// this implies that the edges between big clusters are longer
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edgeLength += (edge.to.clusterSize + edge.from.clusterSize - 2) * this.constants.clustering.edgeGrowth;
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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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if (distance == 0) {
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distance = 0.01;
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}
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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.constants.physics.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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edge.to.springFx -= fx;
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edge.to.springFy -= fy;
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edge.from.springFx += fx;
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edge.from.springFy += fy;
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}
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else {
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var factor = 0.5;
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edge.to.fx -= factor*fx;
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edge.to.fy -= factor*fy;
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edge.from.fx += factor*fx;
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edge.from.fy += factor*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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// normalize spring forces
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var springForce = 1;
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var springFx, springFy;
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for (i = 0; i < nodeIndices.length; i++) {
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var node = nodes[nodeIndices[i]];
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springFx = Math.min(springForce,Math.max(-springForce,node.springFx));
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springFy = Math.min(springForce,Math.max(-springForce,node.springFy));
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node.fx += springFx;
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node.fy += 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 (i = 0; i < nodeIndices.length; i++) {
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var node = nodes[nodeIndices[i]];
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totalFx += node.fx;
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totalFy += node.fy;
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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 (i = 0; i < nodeIndices.length; i++) {
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var node = nodes[nodeIndices[i]];
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node.fx -= correctionFx;
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node.fy -= correctionFy;
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}
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};
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