code: function updateGeometries() {
    if (stackHelper) {
      // move the "light"
      // update light position
      let timer = Date.now() * 0.00025;
      particleLight.position.x = Math.sin(timer * 7) * 70;
      particleLight.position.y = Math.cos(timer * 5) * 80;
      particleLight.position.z = Math.cos(timer * 3) * 90;
  
      // re-draw the line
      line.geometry.vertices[0] = stackHelper.slice.planePosition;
      line.geometry.vertices[1] = particleLight.position;
      line.geometry.verticesNeedUpdate = true;
  
      // update plane direction...
      let dirLPS = new THREE.Vector3(
        particleLight.position.x - stackHelper.slice.planePosition.x,
        particleLight.position.y - stackHelper.slice.planePosition.y,
        particleLight.position.z - stackHelper.slice.planePosition.z
      ).normalize();
  
      // update slice and THEN its border
      stackHelper.slice.planeDirection = dirLPS;
  
      // update border with new slice
      stackHelper.border.helpersSlice = stackHelper.slice;
  
      // update colors based on planeDirection
      let color = rgbToHex(
        Math.round(Math.abs(255 * dirLPS.x)),
        Math.round(Math.abs(255 * dirLPS.y)),
        Math.round(Math.abs(255 * dirLPS.z))
      );
      stackHelper.bbox.color = color;
      stackHelper.border.color = color;
      particleLight.material.color.set(color);
      line.material.color.set(color);
    }
  }
docs: Update geometries