This methods adds a new vertex to the mesh.
| Parameter | Description | 
|---|---|
| position, (x, y, z) | vertex position | 
| normal, (nx, ny, nz) | vertex normal | 
| texcoords, (u, v) | vertex texture coordinates | 
| displacement | maximum tessellation displacement value | 
Returns the index of the new vertex.
Once a mesh has been submitted to the rendering thread, additional vertices cannot be added to it. This occurs during the first call to World::Render after the mesh is created.