X-Git-Url: https://gitweb.ps.run/cloth_sim/blobdiff_plain/19d9f67e228e9925958489574339448bb608c9db..8199b09231f15b0f84480656a0e92827d795fcdc:/Scripts/cloth.js

diff --git a/Scripts/cloth.js b/Scripts/cloth.js
index db07ac3..ff55549 100644
--- a/Scripts/cloth.js
+++ b/Scripts/cloth.js
@@ -1,14 +1,49 @@
+const DAMPING = 0.03;
+const DRAG = 1 - DAMPING;
 const MASS = 0.1;
+const GRAVITY = new THREE.Vector3(0, -9.81 * MASS, 0);
+const K = 1;
+
+const options = {
+  wind: true,
+};
 
 class Constraint {
-  constructor(p1, p2, distance) {
+  constructor(p1, p2, restDist) {
     this.p1 = p1;
     this.p2 = p2;
-    this.distance = distance;
+    this.restDist = restDist;
+  }
+
+  satisfy() {
+    const diff = this.p2.position.clone().sub(this.p1.position);
+    const currentDist = diff.length();
+    if (currentDist == 0) return;
+    if (currentDist <= this.restDist) return;
+    //const correction = diff.multiplyScalar(1 - (this.restDist / currentDist));
+    const correction = diff.multiplyScalar((currentDist - this.restDist) / currentDist);
+    correction.multiplyScalar(K);
+    correction.clampLength(0, 1);
+    const correctionHalf = correction.multiplyScalar(0.5);
+
+    let p1movable = this.p1.movable && this.p1.movableTmp;
+    let p2movable = this.p2.movable && this.p2.movableTmp;
+
+    if (p1movable && p2movable) {
+      this.p1.position.add(correctionHalf);
+      this.p2.position.sub(correctionHalf);
+    } else if (! p1movable && p2movable) {
+      this.p2.position.sub(correction);
+    } else if (p1movable && ! p2movable) {
+      this.p1.position.add(correction);
+    }
   }
 }
 
 class Particle {
+  movableTmp = true;
+  movable = true;
+
   constructor(x, y, z, mass) {
     this.position = new THREE.Vector3(x, y, z);
     this.previous = new THREE.Vector3(x, y, z);
@@ -16,10 +51,25 @@ class Particle {
     this.mass = mass;
   }
   addForce(force) {
-
+    this.acceleration.add(
+      force.clone().multiplyScalar(1/this.mass)
+    );
   }
   verlet(dt) {
+    // verlet algorithm
+    // next position = 2 * current Position - previous position + acceleration * (passed time)^2
+    // acceleration (dv/dt) = F(net)
+    const nextPosition = this.position.clone().sub(this.previous);
+    nextPosition.multiplyScalar(DRAG);
+    nextPosition.add(this.position);
+    nextPosition.add(this.acceleration.multiplyScalar(dt*dt));
 
+    if (this.movable && this.movableTmp) {
+      this.previous = this.position;
+      this.position = nextPosition;
+    }
+
+    this.acceleration.set(0, 0, 0);
   }
 }
 
@@ -29,6 +79,7 @@ class Cloth {
     this.height = height;
     this.numPointsWidth = numPointsWidth;
     this.numPointsHeight = numPointsHeight;
+    this.windFactor = new THREE.Vector3(3, 2, 2);
 
     /**
      * distance between two vertices horizontally/vertically
@@ -55,6 +106,13 @@ class Cloth {
       }
     }
 
+    //this.particles[this.getVertexIndex(0, 0)].movable = false;
+    const n = 3;
+    for (let i = 0; i < numPointsHeight; i++)
+      this.particles[this.getVertexIndex(0, i)].movable = false;
+    //this.particles[this.getVertexIndex(0, numPointsHeight-1)].movable = false;
+    //this.particles[this.getVertexIndex(numPointsWidth-1, 0)].movable = false;
+
     const REST_DIST_X = width / (numPointsWidth-1);
     const REST_DIST_Y = height / (numPointsHeight-1);
 
@@ -71,7 +129,7 @@ class Cloth {
             REST_DIST_X
           ));
         }
-        if (x < numPointsWidth-1) {
+        if (y < numPointsHeight-1) {
           this.constraints.push(new Constraint(
             this.particles[this.getVertexIndex(x, y)],
             this.particles[this.getVertexIndex(x, y+1)],
@@ -126,14 +184,76 @@ class Cloth {
     return geometry;
   }
   updateGeometry(geometry) {
-
+    const positions = geometry.attributes.position.array;
+    for (let i in this.particles) {
+      let p = this.particles[i];
+      positions[i*3+0] = p.position.x;
+      positions[i*3+1] = p.position.y;
+      positions[i*3+2] = p.position.z;
+    }
+    geometry.attributes.position.needsUpdate = true;
+    geometry.computeBoundingSphere();
+    geometry.computeVertexNormals();
   }
-  satisfyConstraints() {
+  simulate(dt) {
+    let now = performance.now();
+    for (let particle of this.particles) {
+      let vertex = particle.position;
+      let fWind = new THREE.Vector3(
+        this.windFactor.x * (Math.sin(vertex.x * vertex.y * now)+1),
+        this.windFactor.y * Math.cos(vertex.z * now),
+        this.windFactor.z * Math.sin(Math.cos(5 * vertex.x * vertex.y * vertex.z))
+      );
+      // normalize then multiply?
+      if (options.wind)
+        particle.addForce(fWind);
+      // calculate wind with normal?
+
+      particle.addForce(GRAVITY);
+
+      particle.verlet(dt);
+    }
+
+    
+    for (let constraint of this.constraints) {
+      constraint.satisfy();
+    }
 
+    this.intersect();
   }
-  simulate() {
 
+  intersect() {
+    let npw = this.numPointsWidth;
+    function getX(i) { return i % npw; }
+    function getY(i) { return Math.floor(i / npw); }
+
+    for (let i in this.particles) {
+      for (let j in this.particles) {  
+        let p1 = this.particles[i];
+        let p2 = this.particles[j];
+
+        p1.movableTmp = true;
+        p2.movableTmp = true;
+
+        if (i == j || (Math.abs(getX(i) - getX(j)) == 1 && Math.abs(getY(i) - getY(j)) == 1))
+          continue;
+
+        let dist = p1.position.distanceTo(p2.position);
+        const collisionDistance = Math.min(this.width / this.numPointsWidth, this.height / this.numPointsHeight);
+        if (dist < collisionDistance) {
+          p1.movableTmp = false;
+          p2.movableTmp = false;
+          let diff = p1.position.clone().sub(p2.position).normalize();
+          diff.multiplyScalar((collisionDistance - dist) * 1.001 / 2);
+          if (p1.movable)
+            p1.position.add(diff);
+          if (p2.movable)
+            p2.position.sub(diff);
+        }
+      }
+    }
   }
+
   /**
    * helper function to calculate index of vertex
    * in "vertices" array based on its x and y positions