Add faces to several separate lines

I have created a scene with several lines of geometries, but all the lines are separated as daughters of the scene, I would like to know how I could add faces to this scene, I hope it is possible, I am developing my degree project: Dissue

So you just want to draw some triangles? You can use this live demo as a starter template.

The code uses a simple BufferGeometry with a position attribute that contains a single triangle.