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64 lines
2.2 KiB
64 lines
2.2 KiB
/**
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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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exports._calculateNodeForces = function () {
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var dx, dy, angle, distance, fx, fy, combinedClusterSize,
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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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// approximation constants
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var a_base = -2 / 3;
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var b = 4 / 3;
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// repulsing forces between nodes
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var nodeDistance = this.constants.physics.repulsion.nodeDistance;
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var minimumDistance = 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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combinedClusterSize = node1.clusterSize + node2.clusterSize - 2;
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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 BarnesHut, 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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minimumDistance = (combinedClusterSize == 0) ? nodeDistance : (nodeDistance * (1 + combinedClusterSize * this.constants.clustering.distanceAmplification));
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var a = a_base / minimumDistance;
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if (distance < 2 * minimumDistance) {
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if (distance < 0.5 * minimumDistance) {
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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 / minimumDistance - 1) * steepness))
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}
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// amplify the repulsion for clusters.
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repulsingForce *= (combinedClusterSize == 0) ? 1 : 1 + combinedClusterSize * this.constants.clustering.forceAmplification;
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repulsingForce = repulsingForce / Math.max(distance,0.01*minimumDistance);
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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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