X-Git-Url: https://gitweb.ps.run/cloth_sim/blobdiff_plain/323d38f395da1cae25ba629d3365c37c30f53fdf..56f6324db4aa55946a6b5ef7de3e1df8b0e22bca:/Scripts/cloth.js

diff --git a/Scripts/cloth.js b/Scripts/cloth.js
index 05ff6f1..aaa9d24 100644
--- a/Scripts/cloth.js
+++ b/Scripts/cloth.js
@@ -1,10 +1,44 @@
-// cloth rendering
-// simulate
-// setup scene
+const DAMPING = 0.03;
+const DRAG = 1 - DAMPING;
+const MASS = 0.35;
+const GRAVITY = new THREE.Vector3(0, -9.81 * MASS, 0);
+const K = 1;
 
-const MASS = 0.1;
+const options = {
+  wind: true,
+};
+
+class Constraint {
+  constructor(p1, p2, restDist) {
+    this.p1 = p1;
+    this.p2 = p2;
+    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);
+    if (this.p1.movable && this.p2.movable) {
+      this.p1.position.add(correctionHalf);
+      this.p2.position.sub(correctionHalf);
+    } else if (! this.p1.movable && this.p2.movable) {
+      this.p2.position.sub(correction);
+    } else if (this.p1.movable && ! this.p2.movable) {
+      this.p1.position.add(correction);
+    }
+  }
+}
 
 class Particle {
+  movable = true;
+
   constructor(x, y, z, mass) {
     this.position = new THREE.Vector3(x, y, z);
     this.previous = new THREE.Vector3(x, y, z);
@@ -12,10 +46,25 @@ 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.previous = this.position;
+      this.position = nextPosition;
+    }
+
+    this.acceleration.set(0, 0, 0);
   }
 }
 
@@ -25,6 +74,7 @@ class Cloth {
     this.height = height;
     this.numPointsWidth = numPointsWidth;
     this.numPointsHeight = numPointsHeight;
+    this.windFactor = new THREE.Vector3(5, 2, 2);
 
     /**
      * distance between two vertices horizontally/vertically
@@ -50,6 +100,39 @@ class Cloth {
         );
       }
     }
+
+    //this.particles[this.getVertexIndex(0, 0)].movable = false;
+    const n = 3;
+    for (let i = 0; i <= n; i++)
+      this.particles[this.getVertexIndex(0, Math.floor((numPointsHeight-1)*(i/n)))].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);
+
+    /**
+     * generate constraints (springs)
+     */
+    this.constraints = [];
+    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)],
+            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)],
+            REST_DIST_Y
+          ));
+        }
+      }
+    }
   }
   generateGeometry() {
     const geometry = new THREE.BufferGeometry();
@@ -68,17 +151,6 @@ class Cloth {
     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;
-    }
-
     /**
      * generate faces based on 4 vertices
      * and 6 springs each
@@ -86,14 +158,14 @@ class Cloth {
     for (let y = 0; y < numPointsHeight - 1; y++) {
       for (let x = 0; x < 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)
         );
       }
     }
@@ -107,6 +179,50 @@ 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();
+  }
+  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();
+    }
+    //console.log(tmpCorrection);
+  }
+  /**
+   * 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;
   }
 }
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