Created
January 1, 2012 21:53
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Force-based Graph Layout in JavaScript
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset=utf-8 /> | |
| <title>Graph Layout</title> | |
| <style> | |
| article, aside, figure, footer, header, hgroup, | |
| menu, nav, section { display: block; } | |
| </style> | |
| </head> | |
| <body> | |
| <p id="hello">Hello World</p> | |
| <script src="layout.js"></script> | |
| </body> | |
| </html> |
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| var MIN_SYSTEM_ENERGY = 1; | |
| var GRAVITY_CONST = 1; | |
| var SPRING_CONST = 1; | |
| var MASS = 1; | |
| var TIME_STEP = 1; | |
| var DAMPING = 0.5; // 0 < damping < 1 | |
| var i, j; | |
| var k, maxSteps = 2; // DEBUG | |
| var u, v; | |
| var dist; | |
| var totalKineticEnergy; | |
| var netForce; | |
| var gravityForceMagnitude; | |
| var springForceMagnitude; | |
| var G = { | |
| vertices: [{ | |
| edges: [1, 4] | |
| }, { | |
| edges: [0, 2, 3, 4] | |
| }, { | |
| edges: [1, 3] | |
| }, { | |
| edges: [1, 2, 4] | |
| }, { | |
| edges: [0, 1, 3] | |
| }] | |
| }; | |
| // set up initial node velocities to (0,0) | |
| for(i = 0; i < G.vertices.length; i += 1) { | |
| G.vertices[i].velocity = {x: 0, y: 0}; | |
| } | |
| // set up initial node positions to (0,0) | |
| for(i = 0; i < G.vertices.length; i += 1) { | |
| var center = {x: 50, y: 50}; | |
| G.vertices[i].position = { | |
| x: center.x + Math.sin(i) * i, | |
| y: center.y + Math.cos(i) * i | |
| }; | |
| } | |
| k = 0; | |
| do { | |
| totalKineticEnergy = 0; | |
| for (i = 0; i < G.vertices.length; i += 1) { | |
| u = G.vertices[i]; | |
| netForce = {x: 0, y: 0}; | |
| for (j = 0; j < G.vertices.length; j += 1) { | |
| if (j !== i) { | |
| v = G.vertices[j]; | |
| dx = v.position.x - u.position.x; | |
| dy = v.position.y - u.position.y; | |
| dist = Math.sqrt(dx * dx + dy * dy); | |
| gravityForceMagnitude = | |
| GRAVITY_CONST * (MASS + MASS) / (dist * dist); | |
| gravityForce = { | |
| x: gravityForceMagnitude * dx / dist, | |
| y: gravityForceMagnitude * dy / dist | |
| }; | |
| netForce.x += gravityForce.x; | |
| netForce.y += gravityForce.y; | |
| } | |
| } | |
| for (j = 0; j < G.vertices[i].edges.length; j += 1) { | |
| v = G.vertices[G.vertices[i].edges[j]]; | |
| dx = v.position.x - u.position.x; | |
| dy = v.position.y - u.position.y; | |
| dist = Math.sqrt(dx * dx + dy * dy); | |
| springForceMagnitude = -SPRING_CONST * dist; | |
| springForce = { | |
| x: springForceMagnitude * dx / dist, | |
| y: springForceMagnitude * dy / dist | |
| }; | |
| netForce.x += springForce.x; | |
| netForce.y += springForce.y; | |
| } | |
| u.velocity = { | |
| x: (u.velocity.x + TIME_STEP * netForce.x) * DAMPING, | |
| y: (u.velocity.y + TIME_STEP * netForce.y) * DAMPING | |
| }; | |
| u.position = { | |
| x: u.position.x + TIME_STEP * u.velocity.x, | |
| y: u.position.y + TIME_STEP * u.velocity.y | |
| }; | |
| // alert('u: ' + JSON.stringify(u)); // DEBUG | |
| // alert('gravityForce: ' + JSON.stringify(gravityForce)); // DEBUG | |
| // alert('springForce: ' + JSON.stringify(springForce)); // DEBUG | |
| // alert('netForce: ' + JSON.stringify(netForce)); // DEBUG | |
| totalKineticEnergy += MASS * | |
| (u.velocity.x * u.velocity.x + u.velocity.y * u.velocity.y); | |
| } | |
| k++; | |
| } while (totalKineticEnergy > MIN_SYSTEM_ENERGY && k < maxSteps); | |
| // alert(totalKineticEnergy); // DEBUG | |
| // alert(k); // DEBUG | |
| if (document.getElementById('hello')) { | |
| document.getElementById('hello').innerHTML = JSON.stringify(G); | |
| } |
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