JavaScript Force Directed Graph

1import {
2    SciChartSurface,
3    NumericAxis,
4    XyDataSeries,
5    XyxyDataSeries,
6    XyScatterRenderableSeries,
7    FastLineSegmentRenderableSeries,
8    EllipsePointMarker,
9    NumberRange,
10    ZoomPanModifier,
11    ZoomExtentsModifier,
12    MouseWheelZoomModifier,
13    PinchZoomModifier,
14    EAutoRange,
15} from "scichart";
16import { appTheme } from "../../../theme";
17import {
18    SimNode,
19    SimEdge,
20    EdgeHoverState,
21    NodeTooltipModifier,
22    NodeDragModifier,
23    NodeHoverPaletteProvider,
24    DragStateRef,
25} from "./nodeModifiers";
26import { AIRPORTS, ROUTES } from "./airportData";
27
28// ─── Build simulation state ───────────────────────────────────────────────────
29
30function buildSimulation(): { nodes: SimNode[]; edges: SimEdge[] } {
31    const iataToIdx = new Map<string, number>();
32    const centerLon = -96;
33    const centerLat = 38;
34    const scaleX = 4.5;
35    const scaleY = 5.5;
36
37    const nodes: SimNode[] = AIRPORTS.map((a, i) => {
38        iataToIdx.set(a.iata, i);
39        const geoX = (a.lon - centerLon) * scaleX;
40        const geoY = (a.lat - centerLat) * scaleY;
41        return { iata: a.iata, label: `${a.iata} – ${a.city}, ${a.state}`, x: geoX, y: geoY, vx: 0, vy: 0, geoX, geoY };
42    });
43
44    const edges: SimEdge[] = ROUTES.map((r) => {
45        const si = iataToIdx.get(r.origin);
46        const ti = iataToIdx.get(r.destination);
47        if (si === undefined || ti === undefined) return null;
48        return { sourceIdx: si, targetIdx: ti };
49    }).filter((e): e is SimEdge => e !== null);
50
51    return { nodes, edges };
52}
53
54// ─── Force simulation tick ────────────────────────────────────────────────────
55
56const REPULSION_STRENGTH = -120;
57const REPULSION_MIN_DIST = 1;
58const SPRING_K = 0.3;
59const SPRING_REST_LENGTH = 20;
60const GEO_ANCHOR_STRENGTH = 0.12;
61const VELOCITY_DECAY = 0.6;
62
63function tick(nodes: SimNode[], edges: SimEdge[], alpha: number): void {
64    for (let i = 0; i < nodes.length; i++) {
65        for (let j = i + 1; j < nodes.length; j++) {
66            const dx = nodes[j].x - nodes[i].x;
67            const dy = nodes[j].y - nodes[i].y;
68            const dist = Math.max(Math.sqrt(dx * dx + dy * dy), REPULSION_MIN_DIST);
69            const force = (REPULSION_STRENGTH * alpha) / (dist * dist);
70            const fx = force * (dx / dist);
71            const fy = force * (dy / dist);
72            nodes[i].vx += fx;
73            nodes[i].vy += fy;
74            nodes[j].vx -= fx;
75            nodes[j].vy -= fy;
76        }
77    }
78
79    for (const edge of edges) {
80        const src = nodes[edge.sourceIdx];
81        const tgt = nodes[edge.targetIdx];
82        const dx = tgt.x + tgt.vx - (src.x + src.vx);
83        const dy = tgt.y + tgt.vy - (src.y + src.vy);
84        const dist = Math.max(Math.sqrt(dx * dx + dy * dy), 1);
85        const force = SPRING_K * (dist - SPRING_REST_LENGTH) * alpha;
86        const fx = force * (dx / dist);
87        const fy = force * (dy / dist);
88        src.vx += fx * 0.5;
89        src.vy += fy * 0.5;
90        tgt.vx -= fx * 0.5;
91        tgt.vy -= fy * 0.5;
92    }
93
94    for (const node of nodes) {
95        node.vx += (node.geoX - node.x) * GEO_ANCHOR_STRENGTH * alpha;
96        node.vy += (node.geoY - node.y) * GEO_ANCHOR_STRENGTH * alpha;
97    }
98
99    for (const node of nodes) {
100        node.vx *= VELOCITY_DECAY;
101        node.vy *= VELOCITY_DECAY;
102        node.x += node.vx;
103        node.y += node.vy;
104    }
105}
106
107// ─── Chart initialization ─────────────────────────────────────────────────────
108
109export const drawExample = async (rootElement: string | HTMLDivElement) => {
110    const { sciChartSurface, wasmContext } = await SciChartSurface.create(rootElement, {
111        theme: appTheme.SciChartJsTheme,
112    });
113
114    const xAxis = new NumericAxis(wasmContext, {
115        isVisible: false,
116        autoRange: EAutoRange.Never,
117        visibleRangeLimit: new NumberRange(-600, 600),
118    });
119    const yAxis = new NumericAxis(wasmContext, {
120        isVisible: false,
121        autoRange: EAutoRange.Never,
122        visibleRangeLimit: new NumberRange(-600, 600),
123    });
124    xAxis.visibleRange = new NumberRange(-300, 300);
125    yAxis.visibleRange = new NumberRange(-300, 300);
126    sciChartSurface.xAxes.add(xAxis);
127    sciChartSurface.yAxes.add(yAxis);
128
129    const { nodes, edges } = buildSimulation();
130
131    const edgeHover = new EdgeHoverState();
132
133    const edgeDataSeries = new XyxyDataSeries(wasmContext);
134    sciChartSurface.renderableSeries.add(
135        new FastLineSegmentRenderableSeries(wasmContext, {
136            dataSeries: edgeDataSeries,
137            stroke: "#47bde650",
138            strokeThickness: 2,
139        })
140    );
141
142    const edgeHighlightDataSeries = new XyxyDataSeries(wasmContext);
143    sciChartSurface.renderableSeries.add(
144        new FastLineSegmentRenderableSeries(wasmContext, {
145            dataSeries: edgeHighlightDataSeries,
146            stroke: "#47bde6",
147            strokeThickness: 3,
148        })
149    );
150
151    const nodeDataSeries = new XyDataSeries(wasmContext);
152    sciChartSurface.renderableSeries.add(
153        new XyScatterRenderableSeries(wasmContext, {
154            dataSeries: nodeDataSeries,
155            pointMarker: new EllipsePointMarker(wasmContext, {
156                width: 14,
157                height: 14,
158                fill: "#274b92",
159                stroke: "#47bde6",
160                strokeThickness: 1.5,
161            }),
162            paletteProvider: new NodeHoverPaletteProvider(edgeHover),
163        })
164    );
165
166    const dragState: DragStateRef = { current: null };
167
168    let alpha = 1.0;
169    let running = true;
170    let loopAlive = false;
171    let autoZoomed = false;
172    let animFrameId: number = 0;
173
174    function frame() {
175        if (!running || sciChartSurface.isDeleted) {
176            loopAlive = false;
177            return;
178        }
179
180        const simActive = alpha >= 0.001 || !!dragState.current;
181
182        if (simActive) {
183            tick(nodes, edges, alpha);
184            alpha *= 0.9772;
185
186            if (!autoZoomed && alpha < 0.5) {
187                autoZoomed = true;
188                sciChartSurface.zoomExtents(200);
189            }
190
191            if (dragState.current) {
192                const n = nodes[dragState.current.nodeIdx];
193                n.x = dragState.current.dataX;
194                n.y = dragState.current.dataY;
195                n.vx = 0;
196                n.vy = 0;
197                alpha = Math.max(alpha, 0.1);
198            }
199        }
200
201        const ex: number[] = [],
202            ey: number[] = [],
203            ex1: number[] = [],
204            ey1: number[] = [];
205        const hx: number[] = [],
206            hy: number[] = [],
207            hx1: number[] = [],
208            hy1: number[] = [];
209        const h = edgeHover.hoveredNodeIdx;
210        for (const edge of edges) {
211            const src = nodes[edge.sourceIdx],
212                tgt = nodes[edge.targetIdx];
213            if (h !== -1 && (edge.sourceIdx === h || edge.targetIdx === h)) {
214                hx.push(src.x);
215                hy.push(src.y);
216                hx1.push(tgt.x);
217                hy1.push(tgt.y);
218            } else {
219                ex.push(src.x);
220                ey.push(src.y);
221                ex1.push(tgt.x);
222                ey1.push(tgt.y);
223            }
224        }
225        edgeDataSeries.clear();
226        edgeDataSeries.appendRange(ex, ey, ex1, ey1);
227        edgeHighlightDataSeries.clear();
228        edgeHighlightDataSeries.appendRange(hx, hy, hx1, hy1);
229
230        nodeDataSeries.clear();
231        nodeDataSeries.appendRange(
232            nodes.map((n) => n.x),
233            nodes.map((n) => n.y)
234        );
235
236        if (simActive) {
237            animFrameId = requestAnimationFrame(frame);
238        } else {
239            loopAlive = false;
240        }
241    }
242
243    function startLoop() {
244        if (!loopAlive) {
245            loopAlive = true;
246            animFrameId = requestAnimationFrame(frame);
247        }
248    }
249
250    sciChartSurface.chartModifiers.add(
251        new NodeTooltipModifier(nodes, edges, edgeHover, () => startLoop()),
252        new NodeDragModifier(nodes, dragState, () => {
253            alpha = Math.max(alpha, 0.3);
254            startLoop();
255        }),
256        new ZoomPanModifier(),
257        new ZoomExtentsModifier(),
258        new MouseWheelZoomModifier(),
259        new PinchZoomModifier()
260    );
261
262    startLoop();
263
264    return {
265        sciChartSurface,
266        wasmContext,
267        stopAnimation: () => {
268            running = false;
269            if (animFrameId) cancelAnimationFrame(animFrameId);
270        },
271    };
272};
273