X-Git-Url: https://gitweb.ps.run/cloth_sim/blobdiff_plain/b9cfb0c7bf25e9ebc0c21e0b32665113ea46f7b5..56f6324db4aa55946a6b5ef7de3e1df8b0e22bca:/Scripts/cloth.js

diff --git a/Scripts/cloth.js b/Scripts/cloth.js
index f1068d4..aaa9d24 100644
--- a/Scripts/cloth.js
+++ b/Scripts/cloth.js
@@ -1,4 +1,228 @@
-// cloth rendering
-// simulate
-// setup scene
-// orbit controls/skybox/flagge
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+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 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);
+    this.acceleration = new THREE.Vector3(0, 0, 0);
+    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);
+  }
+}
+
+class Cloth {
+  constructor(width, height, numPointsWidth, numPointsHeight) {
+    this.width = width;
+    this.height = height;
+    this.numPointsWidth = numPointsWidth;
+    this.numPointsHeight = numPointsHeight;
+    this.windFactor = new THREE.Vector3(5, 2, 2);
+
+    /**
+     * distance between two vertices horizontally/vertically
+     * divide by the number of points minus one
+     * because there are (n - 1) lines between n vertices
+     */
+    let stepWidth = width / (numPointsWidth - 1);
+    let stepHeight = height / (numPointsHeight - 1);
+
+    /**
+     * iterate over the number of vertices in x/y axis
+     * and add a new Particle to "particles"
+     */
+    this.particles = [];
+    for (let y = 0; y < numPointsHeight; y++) {
+      for (let x = 0; x < numPointsWidth; x++) {
+        this.particles.push(
+          new Particle(
+            (x - ((numPointsWidth-1)/2)) * stepWidth,
+            height - (y + ((numPointsHeight-1)/2)) * stepHeight,
+            0,
+            MASS)
+        );
+      }
+    }
+
+    //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();
+
+    const vertices = [];
+    const normals = [];
+    const indices = [];
+
+    for (let particle of this.particles) {
+      vertices.push(
+        particle.position.x,
+        particle.position.y,
+        particle.position.z);
+    }
+
+    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++) {
+        indices.push(
+          this.getVertexIndex(x, y),
+          this.getVertexIndex(x+1, y),
+          this.getVertexIndex(x+1, y+1)
+        );
+        indices.push(
+          this.getVertexIndex(x, y),
+          this.getVertexIndex(x+1, y+1),
+          this.getVertexIndex(x, y+1)
+        );
+      }
+    }
+
+    geometry.setIndex(indices);
+    geometry.setAttribute('position', new THREE.Float32BufferAttribute(vertices, 3));
+    //geometry.setAttribute('normal', new THREE.Float32BufferAttribute(normals, 3));
+    geometry.computeBoundingSphere();
+    geometry.computeVertexNormals();
+
+    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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