X-Git-Url: https://gitweb.ps.run/cloth_sim/blobdiff_plain/323d38f395da1cae25ba629d3365c37c30f53fdf..refs/heads/refactoring:/Scripts/cloth.js?ds=sidebyside

diff --git a/Scripts/cloth.js b/Scripts/cloth.js
index 05ff6f1..712ed63 100644
--- a/Scripts/cloth.js
+++ b/Scripts/cloth.js
@@ -1,10 +1,54 @@
-// cloth rendering
-// simulate
-// setup scene
-
+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 MAX_STRETCH = 1.5;
+
+const options = {
+  wind: true,
+};
+
+class Spring {
+  constructor(p1, p2, restDist) {
+    this.p1 = p1;
+    this.p2 = p2;
+    this.restDist = restDist;
+  }
+
+  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);
+    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);
+    } else if (! p1movable && p2movable) {
+      this.p2.position.sub(correction);
+    } else if (p1movable && ! p2movable) {
+      this.p1.position.add(correction);
+    }
+  }
+}
+
+class Mass {
+  movableTmp = true;
+  movable = true;
 
-class Particle {
   constructor(x, y, z, mass) {
     this.position = new THREE.Vector3(x, y, z);
     this.previous = new THREE.Vector3(x, y, z);
@@ -12,10 +56,29 @@ 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)
+    /** 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));
 
+    if (this.movable && this.movableTmp) {
+      this.previous = this.position;
+      this.position = nextPosition;
+    }
+
+    /** reset for next frame */
+    this.acceleration.set(0, 0, 0);
   }
 }
 
@@ -25,6 +88,7 @@ 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
@@ -36,13 +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,
@@ -50,63 +114,204 @@ class Cloth {
         );
       }
     }
+
+    /** attach cloth to flag pole */
+    const n = 3;
+    for (let i = 0; i < numPointsHeight; i++)
+      this.masses[this.getVertexIndex(0, i)].movable = false;
+
+    const REST_DIST_X = width / (numPointsWidth-1);
+    const REST_DIST_Y = height / (numPointsHeight-1);
+
+    /**
+     * generate springs (constraints)
+     */
+    this.springs = [];
+    for (let y = 0; y < numPointsHeight; y++) {
+      for (let x = 0; x < numPointsWidth; x++) {
+        if (x < numPointsWidth-1) {
+          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.springs.push(new Spring(
+            this.masses[this.getVertexIndex(x, y)],
+            this.masses[this.getVertexIndex(x, y+1)],
+            REST_DIST_Y
+          ));
+        }
+      }
+    }
   }
   generateGeometry() {
     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);
-    }
-
-    const numPointsWidth = this.numPointsWidth;
-    const numPointsHeight = this.numPointsHeight;
-
-    /**
-     * helper function to calculate index of vertex
-     * in "vertices" array based on its x and y positions
-     * in the mesh
-     * @param {number} x - x index of vertex
-     * @param {number} y - y index of vertex
-     */
-    function getVertexIndex(x, y) {
-      return y * numPointsWidth + x;
+      uvs.push(
+        this.getX(i) / (this.numPointsWidth-1),
+        1 - (this.getY(i) / (this.numPointsHeight-1))
+      );
     }
 
     /**
      * 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(
-          getVertexIndex(x, y),
-          getVertexIndex(x+1, y),
-          getVertexIndex(x+1, y+1)
+          this.getVertexIndex(x, y),
+          this.getVertexIndex(x+1, y),
+          this.getVertexIndex(x+1, y+1)
         );
         indices.push(
-          getVertexIndex(x, y),
-          getVertexIndex(x+1, y+1),
-          getVertexIndex(x, y+1)
+          this.getVertexIndex(x, y),
+          this.getVertexIndex(x+1, y+1),
+          this.getVertexIndex(x, y+1)
         );
       }
     }
 
+    /** 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.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 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),
+        this.windFactor.z * Math.sin(Math.cos(5 * vertex.x * vertex.y * vertex.z))
+      );
+      // normalize then multiply?
+      if (options.wind)
+        mass.addForce(fWind);
+      // calculate wind with normal?
+
+      mass.addForce(GRAVITY);
+
+      /** integrate motion */
+      mass.verlet(dt);
+    }
+
+    /** run satisfy step */
+    for (let constraint of this.springs) {
+      constraint.satisfy();
+    }
+
+    /** prevent self-intersections */
+    this.intersect();
+  }
+
+  intersect() {
+    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;
+
+        /** 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);
+        /** 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;
+
+          /** 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(diffP2P1);
+            //p1.position.add(diffP2P1.multiplyScalar(factor1));
+          if (p2.movable)
+            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
+   * in "vertices" array based on its x and y positions
+   * in the mesh
+   * @param {number} x - x index of vertex
+   * @param {number} y - y index of vertex
+   */
+  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