With THREE.ConvexGeometry, we can create a convex hull from a set of points. A convex hull is the minimal shape that encompasses all these points. The easiest way to understand this is by looking at an example. If you open up the 01-advanced-3d-geometries-convex.html example, you'll see the convex hull for a random set of points. The following screenshot shows this geometry:
In this example, we generate a random set of points, and based on these points, we create THREE.ConvexGeometry. In the example, you can click on redraw, which will generate 20 new points and draw the convex hull. If you try this for yourself, enable the material's transparency and set the opacity to a level below 1 to see the points that are used to create this geometry. These points are created as small THREE.SphereGeometry ...