X-Git-Url: https://gitweb.ps.run/cloth_sim/blobdiff_plain/8199b09231f15b0f84480656a0e92827d795fcdc..f97f4ee25759ffaa6a4d4709f45fc8b7b5b24973:/Scripts/cloth.js

diff --git a/Scripts/cloth.js b/Scripts/cloth.js
index ff55549..712ed63 100644
--- a/Scripts/cloth.js
+++ b/Scripts/cloth.js
@@ -3,12 +3,13 @@ const DRAG = 1 - DAMPING;
 const MASS = 0.1;
 const GRAVITY = new THREE.Vector3(0, -9.81 * MASS, 0);
 const K = 1;
+const MAX_STRETCH = 1.5;
 
 const options = {
   wind: true,
 };
 
-class Constraint {
+class Spring {
   constructor(p1, p2, restDist) {
     this.p1 = p1;
     this.p2 = p2;
@@ -16,19 +17,23 @@ class Constraint {
   }
 
   satisfy() {
+    /** calculate current spring length */
     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));
+
+    /** calculate necessary correction length and direction */
     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;
 
+    /** apply correction if masses aren't fixed */
+    /** divide correction if both are movable */
     if (p1movable && p2movable) {
       this.p1.position.add(correctionHalf);
       this.p2.position.sub(correctionHalf);
@@ -40,7 +45,7 @@ class Constraint {
   }
 }
 
-class Particle {
+class Mass {
   movableTmp = true;
   movable = true;
 
@@ -59,8 +64,11 @@ class Particle {
     // verlet algorithm
     // next position = 2 * current Position - previous position + acceleration * (passed time)^2
     // acceleration (dv/dt) = F(net)
+    /** calculate velocity */
     const nextPosition = this.position.clone().sub(this.previous);
+    /** apply drag */
     nextPosition.multiplyScalar(DRAG);
+    /** add to current position and add acceleration */
     nextPosition.add(this.position);
     nextPosition.add(this.acceleration.multiplyScalar(dt*dt));
 
@@ -69,6 +77,7 @@ class Particle {
       this.position = nextPosition;
     }
 
+    /** reset for next frame */
     this.acceleration.set(0, 0, 0);
   }
 }
@@ -91,13 +100,13 @@ class Cloth {
 
     /**
      * iterate over the number of vertices in x/y axis
-     * and add a new Particle to "particles"
+     * and add a new Particle to "masses"
      */
-    this.particles = [];
+    this.masses = [];
     for (let y = 0; y < numPointsHeight; y++) {
       for (let x = 0; x < numPointsWidth; x++) {
-        this.particles.push(
-          new Particle(
+        this.masses.push(
+          new Mass(
             (x - ((numPointsWidth-1)/2)) * stepWidth,
             height - (y + ((numPointsHeight-1)/2)) * stepHeight,
             0,
@@ -106,33 +115,31 @@ class Cloth {
       }
     }
 
-    //this.particles[this.getVertexIndex(0, 0)].movable = false;
+    /** attach cloth to flag pole */
     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;
+      this.masses[this.getVertexIndex(0, i)].movable = false;
 
     const REST_DIST_X = width / (numPointsWidth-1);
     const REST_DIST_Y = height / (numPointsHeight-1);
 
     /**
-     * generate constraints (springs)
+     * generate springs (constraints)
      */
-    this.constraints = [];
+    this.springs = [];
     for (let y = 0; y < numPointsHeight; y++) {
       for (let x = 0; x < numPointsWidth; x++) {
         if (x < numPointsWidth-1) {
-          this.constraints.push(new Constraint(
-            this.particles[this.getVertexIndex(x, y)],
-            this.particles[this.getVertexIndex(x+1, y)],
+          this.springs.push(new Spring(
+            this.masses[this.getVertexIndex(x, y)],
+            this.masses[this.getVertexIndex(x+1, y)],
             REST_DIST_X
           ));
         }
         if (y < numPointsHeight-1) {
-          this.constraints.push(new Constraint(
-            this.particles[this.getVertexIndex(x, y)],
-            this.particles[this.getVertexIndex(x, y+1)],
+          this.springs.push(new Spring(
+            this.masses[this.getVertexIndex(x, y)],
+            this.masses[this.getVertexIndex(x, y+1)],
             REST_DIST_Y
           ));
         }
@@ -143,25 +150,28 @@ class Cloth {
     const geometry = new THREE.BufferGeometry();
 
     const vertices = [];
-    const normals = [];
     const indices = [];
+    const uvs = [];
 
-    for (let particle of this.particles) {
+    /** create one vertex and one uv coordinate per mass */
+    for (let i in this.masses) {
+      let particle = this.masses[i];
       vertices.push(
         particle.position.x,
         particle.position.y,
         particle.position.z);
+      uvs.push(
+        this.getX(i) / (this.numPointsWidth-1),
+        1 - (this.getY(i) / (this.numPointsHeight-1))
+      );
     }
 
-    const numPointsWidth = this.numPointsWidth;
-    const numPointsHeight = this.numPointsHeight;
-
     /**
      * generate faces based on 4 vertices
      * and 6 springs each
      */
-    for (let y = 0; y < numPointsHeight - 1; y++) {
-      for (let x = 0; x < numPointsWidth - 1; x++) {
+    for (let y = 0; y < this.numPointsHeight - 1; y++) {
+      for (let x = 0; x < this.numPointsWidth - 1; x++) {
         indices.push(
           this.getVertexIndex(x, y),
           this.getVertexIndex(x+1, y),
@@ -175,30 +185,37 @@ class Cloth {
       }
     }
 
+    /** set up geometry */
     geometry.setIndex(indices);
     geometry.setAttribute('position', new THREE.Float32BufferAttribute(vertices, 3));
-    //geometry.setAttribute('normal', new THREE.Float32BufferAttribute(normals, 3));
+    geometry.setAttribute('uv', new THREE.Float32BufferAttribute(uvs, 2));
     geometry.computeBoundingSphere();
     geometry.computeVertexNormals();
 
     return geometry;
   }
   updateGeometry(geometry) {
+    /** update vertex positions in place */
     const positions = geometry.attributes.position.array;
-    for (let i in this.particles) {
-      let p = this.particles[i];
+    for (let i in this.masses) {
+      let p = this.masses[i];
       positions[i*3+0] = p.position.x;
       positions[i*3+1] = p.position.y;
       positions[i*3+2] = p.position.z;
     }
+    /** update internally and recalculate bounding volume */
     geometry.attributes.position.needsUpdate = true;
     geometry.computeBoundingSphere();
     geometry.computeVertexNormals();
   }
   simulate(dt) {
     let now = performance.now();
-    for (let particle of this.particles) {
-      let vertex = particle.position;
+    for (let mass of this.masses) {
+      /** accumulate acceleration:
+       *  - wind
+       *  - gravity
+       */
+      let vertex = mass.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),
@@ -206,53 +223,84 @@ class Cloth {
       );
       // normalize then multiply?
       if (options.wind)
-        particle.addForce(fWind);
+        mass.addForce(fWind);
       // calculate wind with normal?
 
-      particle.addForce(GRAVITY);
+      mass.addForce(GRAVITY);
 
-      particle.verlet(dt);
+      /** integrate motion */
+      mass.verlet(dt);
     }
 
-    
-    for (let constraint of this.constraints) {
+    /** run satisfy step */
+    for (let constraint of this.springs) {
       constraint.satisfy();
     }
 
+    /** prevent self-intersections */
     this.intersect();
   }
 
   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];
+    for (let i in this.masses) {
+      for (let j in this.masses) {  
+        let p1 = this.masses[i];
+        let p2 = this.masses[j];
 
         p1.movableTmp = true;
         p2.movableTmp = true;
 
-        if (i == j || (Math.abs(getX(i) - getX(j)) == 1 && Math.abs(getY(i) - getY(j)) == 1))
+        /** skip if i == j or if masses are adjacent */
+        if (i == j || (Math.abs(this.getX(i) - this.getX(j)) == 1 && Math.abs(this.getY(i) - this.getY(j)) == 1))
           continue;
 
+        /** calculate distance of points  */
         let dist = p1.position.distanceTo(p2.position);
-        const collisionDistance = Math.min(this.width / this.numPointsWidth, this.height / this.numPointsHeight);
+        /** calculate minimal resting distance (largest distance that should not be fallen below) */
+        let collisionDistance = Math.min(this.width / this.numPointsWidth, this.height / this.numPointsHeight);
+        // collisionDistance /= 2;
+        /** calculate "sphere intersection" */
         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);
+          // p1.movableTmp = false;
+          // p2.movableTmp = false;
+
+          /** vectors from p1 to p2 and the other way round */
+          let diffP2P1 = p1.position.clone().sub(p2.position).normalize();
+          diffP2P1.multiplyScalar((collisionDistance - dist) * 1.001 / 2);
+          let diffP1P2 = diffP2P1.clone().multiplyScalar(-1);
+
+          // let v1 = p1.position.clone().sub(p1.previous).normalize();
+          // let v2 = p2.position.clone().sub(p2.previous).normalize();
+
+          // let factor1 = (Math.PI - Math.acos(v1.dot(diffP2P1))) / Math.PI * 2;
+          // let factor2 = (Math.PI - Math.acos(v2.dot(diffP1P2))) / Math.PI * 2;
+
+          /** move masses apart */
           if (p1.movable)
-            p1.position.add(diff);
+            p1.position.add(diffP2P1);
+            //p1.position.add(diffP2P1.multiplyScalar(factor1));
           if (p2.movable)
-            p2.position.sub(diff);
+            p2.position.add(diffP1P2);
+            //p2.position.add(diffP1P2.multiplyScalar(factor2));
         }
       }
     }
   }
+  blow(camPos, intersects) {
+    let face = intersects[0].face;
+    /** vector from cam to intersection (wind) */
+    let dir = intersects[0].point.clone().sub(camPos).multiplyScalar(100);
+    /** apply to all vertices of affected face */
+    this.masses[face.a].addForce(dir);
+    this.masses[face.b].addForce(dir);
+    this.masses[face.c].addForce(dir);
+  }
+  drag(mousePosWorld, index) {
+    /** calculate vector from vertex to cursor */
+    let dir = mousePosWorld.clone().sub(this.masses[index].position).multiplyScalar(200);
+    /** apply to grabbed vertex */
+    this.masses[index].addForce(dir);
+  }
 
   /**
    * helper function to calculate index of vertex
@@ -264,4 +312,6 @@ class Cloth {
   getVertexIndex(x, y) {
     return y * this.numPointsWidth + x;
   }
+  getX(i) { return i % this.numPointsWidth; }
+  getY(i) { return Math.floor(i / this.numPointsWidth); }
 }
\ No newline at end of file