-// 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
+const MAX_STRETCH = 1.5;\r
+\r
+const options = {\r
+ wind: true,\r
+};\r
+\r
+class Spring {\r
+ constructor(p1, p2, restDist) {\r
+ this.p1 = p1;\r
+ this.p2 = p2;\r
+ this.restDist = restDist;\r
+ }\r
+\r
+ satisfy() {\r
+ /** calculate current spring length */\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
+\r
+ /** calculate necessary correction length and direction */\r
+ const correction = diff.multiplyScalar((currentDist - this.restDist) / currentDist);\r
+ correction.multiplyScalar(K);\r
+ const correctionHalf = correction.multiplyScalar(0.5);\r
+\r
+ let p1movable = this.p1.movable && this.p1.movableTmp;\r
+ let p2movable = this.p2.movable && this.p2.movableTmp;\r
+\r
+ /** apply correction if masses aren't fixed */\r
+ /** divide correction if both are movable */\r
+ if (p1movable && p2movable) {\r
+ this.p1.position.add(correctionHalf);\r
+ this.p2.position.sub(correctionHalf);\r
+ } else if (! p1movable && p2movable) {\r
+ this.p2.position.sub(correction);\r
+ } else if (p1movable && ! p2movable) {\r
+ this.p1.position.add(correction);\r
+ }\r
+ }\r
+}\r
+\r
+class Mass {\r
+ movableTmp = true;\r
+ movable = true;\r
\r
-class Particle {\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
+ /** calculate velocity */\r
+ const nextPosition = this.position.clone().sub(this.previous);\r
+ /** apply drag */\r
+ nextPosition.multiplyScalar(DRAG);\r
+ /** add to current position and add acceleration */\r
+ nextPosition.add(this.position);\r
+ nextPosition.add(this.acceleration.multiplyScalar(dt*dt));\r
\r
+ if (this.movable && this.movableTmp) {\r
+ this.previous = this.position;\r
+ this.position = nextPosition;\r
+ }\r
+\r
+ /** reset for next frame */\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(3, 2, 2);\r
\r
/**\r
* distance between two vertices horizontally/vertically\r
\r
/**\r
* iterate over the number of vertices in x/y axis\r
- * and add a new Particle to "particles"\r
+ * and add a new Particle to "masses"\r
*/\r
- this.particles = [];\r
+ this.masses = [];\r
for (let y = 0; y < numPointsHeight; y++) {\r
for (let x = 0; x < numPointsWidth; x++) {\r
- this.particles.push(\r
- new Particle(\r
+ this.masses.push(\r
+ new Mass(\r
(x - ((numPointsWidth-1)/2)) * stepWidth,\r
height - (y + ((numPointsHeight-1)/2)) * stepHeight,\r
0,\r
);\r
}\r
}\r
+\r
+ /** attach cloth to flag pole */\r
+ const n = 3;\r
+ for (let i = 0; i < numPointsHeight; i++)\r
+ this.masses[this.getVertexIndex(0, i)].movable = false;\r
+\r
+ const REST_DIST_X = width / (numPointsWidth-1);\r
+ const REST_DIST_Y = height / (numPointsHeight-1);\r
+\r
+ /**\r
+ * generate springs (constraints)\r
+ */\r
+ this.springs = [];\r
+ for (let y = 0; y < numPointsHeight; y++) {\r
+ for (let x = 0; x < numPointsWidth; x++) {\r
+ if (x < numPointsWidth-1) {\r
+ this.springs.push(new Spring(\r
+ this.masses[this.getVertexIndex(x, y)],\r
+ this.masses[this.getVertexIndex(x+1, y)],\r
+ REST_DIST_X\r
+ ));\r
+ }\r
+ if (y < numPointsHeight-1) {\r
+ this.springs.push(new Spring(\r
+ this.masses[this.getVertexIndex(x, y)],\r
+ this.masses[this.getVertexIndex(x, y+1)],\r
+ REST_DIST_Y\r
+ ));\r
+ }\r
+ }\r
+ }\r
}\r
generateGeometry() {\r
const geometry = new THREE.BufferGeometry();\r
\r
const vertices = [];\r
- const normals = [];\r
const indices = [];\r
+ const uvs = [];\r
\r
- for (let particle of this.particles) {\r
+ /** create one vertex and one uv coordinate per mass */\r
+ for (let i in this.masses) {\r
+ let particle = this.masses[i];\r
vertices.push(\r
particle.position.x,\r
particle.position.y,\r
particle.position.z);\r
- }\r
-\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
+ uvs.push(\r
+ this.getX(i) / (this.numPointsWidth-1),\r
+ 1 - (this.getY(i) / (this.numPointsHeight-1))\r
+ );\r
}\r
\r
/**\r
* generate faces based on 4 vertices\r
* and 6 springs each\r
*/\r
- for (let y = 0; y < numPointsHeight - 1; y++) {\r
- for (let x = 0; x < numPointsWidth - 1; x++) {\r
+ for (let y = 0; y < this.numPointsHeight - 1; y++) {\r
+ for (let x = 0; x < this.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
\r
+ /** set up geometry */\r
geometry.setIndex(indices);\r
geometry.setAttribute('position', new THREE.Float32BufferAttribute(vertices, 3));\r
- //geometry.setAttribute('normal', new THREE.Float32BufferAttribute(normals, 3));\r
+ geometry.setAttribute('uv', new THREE.Float32BufferAttribute(uvs, 2));\r
geometry.computeBoundingSphere();\r
geometry.computeVertexNormals();\r
\r
return geometry;\r
}\r
updateGeometry(geometry) {\r
+ /** update vertex positions in place */\r
+ const positions = geometry.attributes.position.array;\r
+ for (let i in this.masses) {\r
+ let p = this.masses[i];\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
+ }\r
+ /** update internally and recalculate bounding volume */\r
+ geometry.attributes.position.needsUpdate = true;\r
+ geometry.computeBoundingSphere();\r
+ geometry.computeVertexNormals();\r
+ }\r
+ simulate(dt) {\r
+ let now = performance.now();\r
+ for (let mass of this.masses) {\r
+ /** accumulate acceleration:\r
+ * - wind\r
+ * - gravity\r
+ */\r
+ let vertex = mass.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
+ if (options.wind)\r
+ mass.addForce(fWind);\r
+ // calculate wind with normal?\r
+\r
+ mass.addForce(GRAVITY);\r
+\r
+ /** integrate motion */\r
+ mass.verlet(dt);\r
+ }\r
+\r
+ /** run satisfy step */\r
+ for (let constraint of this.springs) {\r
+ constraint.satisfy();\r
+ }\r
+\r
+ /** prevent self-intersections */\r
+ this.intersect();\r
+ }\r
+\r
+ intersect() {\r
+ for (let i in this.masses) {\r
+ for (let j in this.masses) { \r
+ let p1 = this.masses[i];\r
+ let p2 = this.masses[j];\r
+\r
+ p1.movableTmp = true;\r
+ p2.movableTmp = true;\r
+\r
+ /** skip if i == j or if masses are adjacent */\r
+ if (i == j || (Math.abs(this.getX(i) - this.getX(j)) == 1 && Math.abs(this.getY(i) - this.getY(j)) == 1))\r
+ continue;\r
+\r
+ /** calculate distance of points */\r
+ let dist = p1.position.distanceTo(p2.position);\r
+ /** calculate minimal resting distance (largest distance that should not be fallen below) */\r
+ let collisionDistance = Math.min(this.width / this.numPointsWidth, this.height / this.numPointsHeight);\r
+ // collisionDistance /= 2;\r
+ /** calculate "sphere intersection" */\r
+ if (dist < collisionDistance) {\r
+ // p1.movableTmp = false;\r
+ // p2.movableTmp = false;\r
+\r
+ /** vectors from p1 to p2 and the other way round */\r
+ let diffP2P1 = p1.position.clone().sub(p2.position).normalize();\r
+ diffP2P1.multiplyScalar((collisionDistance - dist) * 1.001 / 2);\r
+ let diffP1P2 = diffP2P1.clone().multiplyScalar(-1);\r
+\r
+ // let v1 = p1.position.clone().sub(p1.previous).normalize();\r
+ // let v2 = p2.position.clone().sub(p2.previous).normalize();\r
+\r
+ // let factor1 = (Math.PI - Math.acos(v1.dot(diffP2P1))) / Math.PI * 2;\r
+ // let factor2 = (Math.PI - Math.acos(v2.dot(diffP1P2))) / Math.PI * 2;\r
+\r
+ /** move masses apart */\r
+ if (p1.movable)\r
+ p1.position.add(diffP2P1);\r
+ //p1.position.add(diffP2P1.multiplyScalar(factor1));\r
+ if (p2.movable)\r
+ p2.position.add(diffP1P2);\r
+ //p2.position.add(diffP1P2.multiplyScalar(factor2));\r
+ }\r
+ }\r
+ }\r
+ }\r
+ blow(camPos, intersects) {\r
+ let face = intersects[0].face;\r
+ /** vector from cam to intersection (wind) */\r
+ let dir = intersects[0].point.clone().sub(camPos).multiplyScalar(100);\r
+ /** apply to all vertices of affected face */\r
+ this.masses[face.a].addForce(dir);\r
+ this.masses[face.b].addForce(dir);\r
+ this.masses[face.c].addForce(dir);\r
+ }\r
+ drag(mousePosWorld, index) {\r
+ /** calculate vector from vertex to cursor */\r
+ let dir = mousePosWorld.clone().sub(this.masses[index].position).multiplyScalar(200);\r
+ /** apply to grabbed vertex */\r
+ this.masses[index].addForce(dir);\r
+ }\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
+ getX(i) { return i % this.numPointsWidth; }\r
+ getY(i) { return Math.floor(i / this.numPointsWidth); }\r
}
\ No newline at end of file
projects / cloth_sim / blobdiff