minetest_vector.lua

-- register line
minetest.registry_line({
   initial_properties = { 
      color = "black", 
      width = "10"
   },
   
   on_touch = function(player, ....) {

   }
   
}, "minetest:simple_line")

local entity1 = minetest.add_entity(pos1, "minetest:entity1")
local entity2 = minetest.add_entity(pos2, "minetest:entity1")

-- draw the edge between two entities
local line = minetest.add_line(entity1, entity2, "minetest.simple_vector")

-- in an ideal world, after entities with an edge change position, the line redrawn too
entity1:set_pos(pos3)

-- when one of the entities is deleted, the vector between entities should be removed too.
-- for eample
entity2:remove()  --should call line:remove() somewhere in minetest engine

-- change line color and width
line:set_properties({
   color: "red",
   width: "11",
})
   
   
-- some useful things
local lines = entity1.get_lines()