The PointMesh is made from a single point. Instead of relying on triangles, points are rendered as a single rectangle on the screen with a constant size. They are intended to be used with Particle systems, but can be used as a cheap way to render constant size billboarded sprites (for example in a point cloud).
PointMeshes, must be used with a material that has a point size. Point size can be accessed in a shader with [code]POINT_SIZE[/code], or in a [SpatialMaterial] by setting [member Material3D.flags_use_point_size] and the variable [member Material3D.params_point_size].
