-// cloth rendering\r
-// simulate\r
-// setup scene\r
-\r
+const DAMPING = 0.03;\r
+const DRAG = 1 - DAMPING;\r
const MASS = 0.1;\r
+const GRAVITY = new THREE.Vector3(0, -9.81 * MASS, 0);\r
+const K = 1;\r
+\r
+let tmpCorrection;\r
+\r
+class Constraint {\r
+ constructor(p1, p2, restDist) {\r
+ this.p1 = p1;\r
+ this.p2 = p2;\r
+ this.restDist = restDist;\r
+ }\r
+\r
+ satisfy() {\r
+ const diff = this.p2.position.clone().sub(this.p1.position);\r
+ const currentDist = diff.length();\r
+ if (currentDist == 0) return;\r
+ if (currentDist <= this.restDist) return;\r
+ const correction = diff.multiplyScalar(1 - (this.restDist / currentDist));\r
+ correction.multiplyScalar(K);\r
+ tmpCorrection = correction;\r
+ const correctionHalf = correction.multiplyScalar(0.5);\r
+ this.p1.position.add(correctionHalf);\r
+ this.p2.position.sub(correctionHalf);\r
+ }\r
+}\r
\r
class Particle {\r
+ movable = true;\r
+\r
constructor(x, y, z, mass) {\r
this.position = new THREE.Vector3(x, y, z);\r
this.previous = new THREE.Vector3(x, y, z);\r
this.mass = mass;\r
}\r
addForce(force) {\r
-\r
+ this.acceleration.add(\r
+ force.clone().multiplyScalar(1/this.mass)\r
+ );\r
}\r
verlet(dt) {\r
+ // verlet algorithm\r
+ // next position = 2 * current Position - previous position + acceleration * (passed time)^2\r
+ // acceleration (dv/dt) = F(net)\r
+ const nextPosition = this.position.clone().sub(this.previous);\r
+ nextPosition.multiplyScalar(DRAG);\r
+ nextPosition.add(this.position);\r
+ nextPosition.add(this.acceleration.multiplyScalar(dt*dt));\r
\r
+ this.previous = this.position;\r
+ this.position = nextPosition;\r
+\r
+ this.acceleration.set(0, 0, 0);\r
}\r
}\r
\r
this.height = height;\r
this.numPointsWidth = numPointsWidth;\r
this.numPointsHeight = numPointsHeight;\r
+ this.windFactor = new THREE.Vector3(0.5, 0.2, 0.2);\r
\r
/**\r
* distance between two vertices horizontally/vertically\r
);\r
}\r
}\r
+\r
+ this.particles[this.getVertexIndex(0, 0)].movable = false;\r
+ this.particles[this.getVertexIndex(0, numPointsHeight-1)].movable = false;\r
+ this.particles[this.getVertexIndex(numPointsWidth-1, 0)].movable = false;\r
+\r
+ const REST_DIST_X = width / (numPointsWidth-1);\r
+ const REST_DIST_Y = height / (numPointsHeight-1);\r
+\r
+ /**\r
+ * generate constraints (springs)\r
+ */\r
+ this.constraints = [];\r
+ for (let y = 0; y < numPointsHeight; y++) {\r
+ for (let x = 0; x < numPointsWidth; x++) {\r
+ if (x < numPointsWidth-1) {\r
+ this.constraints.push(new Constraint(\r
+ this.particles[this.getVertexIndex(x, y)],\r
+ this.particles[this.getVertexIndex(x+1, y)],\r
+ REST_DIST_X\r
+ ));\r
+ }\r
+ if (y < numPointsHeight-1) {\r
+ this.constraints.push(new Constraint(\r
+ this.particles[this.getVertexIndex(x, y)],\r
+ this.particles[this.getVertexIndex(x, y+1)],\r
+ REST_DIST_Y\r
+ ));\r
+ }\r
+ }\r
+ }\r
}\r
generateGeometry() {\r
const geometry = new THREE.BufferGeometry();\r
const numPointsWidth = this.numPointsWidth;\r
const numPointsHeight = this.numPointsHeight;\r
\r
- /**\r
- * helper function to calculate index of vertex\r
- * in "vertices" array based on its x and y positions\r
- * in the mesh\r
- * @param {number} x - x index of vertex\r
- * @param {number} y - y index of vertex\r
- */\r
- function getVertexIndex(x, y) {\r
- return y * numPointsWidth + x;\r
- }\r
-\r
/**\r
* generate faces based on 4 vertices\r
* and 6 springs each\r
for (let y = 0; y < numPointsHeight - 1; y++) {\r
for (let x = 0; x < numPointsWidth - 1; x++) {\r
indices.push(\r
- getVertexIndex(x, y),\r
- getVertexIndex(x+1, y),\r
- getVertexIndex(x+1, y+1)\r
+ this.getVertexIndex(x, y),\r
+ this.getVertexIndex(x+1, y),\r
+ this.getVertexIndex(x+1, y+1)\r
);\r
indices.push(\r
- getVertexIndex(x, y),\r
- getVertexIndex(x+1, y+1),\r
- getVertexIndex(x, y+1)\r
+ this.getVertexIndex(x, y),\r
+ this.getVertexIndex(x+1, y+1),\r
+ this.getVertexIndex(x, y+1)\r
);\r
}\r
}\r
return geometry;\r
}\r
updateGeometry(geometry) {\r
+ const positions = geometry.attributes.position.array;\r
+ for (let i in this.particles) {\r
+ let p = this.particles[i];\r
+ if (p.movable) {\r
+ positions[i*3+0] = p.position.x;\r
+ positions[i*3+1] = p.position.y;\r
+ positions[i*3+2] = p.position.z;\r
+ } else {\r
+ p.position = p.previous;\r
+ }\r
+ }\r
+ geometry.attributes.position.needsUpdate = true;\r
+ geometry.computeBoundingSphere();\r
+ geometry.computeVertexNormals();\r
+ }\r
+ simulate(dt) {\r
+ let now = performance.now();\r
+ for (let particle of this.particles) {\r
+ let vertex = particle.position;\r
+ let fWind = new THREE.Vector3(\r
+ this.windFactor.x * (Math.sin(vertex.x * vertex.y * now)+1),\r
+ this.windFactor.y * Math.cos(vertex.z * now),\r
+ this.windFactor.z * Math.sin(Math.cos(5 * vertex.x * vertex.y * vertex.z))\r
+ );\r
+ // normalize then multiply?\r
+ particle.addForce(fWind);\r
+ // calculate wind with normal?\r
+\r
+ particle.addForce(GRAVITY);\r
\r
+ particle.verlet(dt);\r
+ }\r
+\r
+ \r
+ for (let constraint of this.constraints) {\r
+ constraint.satisfy();\r
+ }\r
+ //console.log(tmpCorrection);\r
+ }\r
+ /**\r
+ * helper function to calculate index of vertex\r
+ * in "vertices" array based on its x and y positions\r
+ * in the mesh\r
+ * @param {number} x - x index of vertex\r
+ * @param {number} y - y index of vertex\r
+ */\r
+ getVertexIndex(x, y) {\r
+ return y * this.numPointsWidth + x;\r
}\r
}
\ No newline at end of file
projects / cloth_sim / blobdiff