lua.box2d.body.convert
x,y = body:convert(x,y,conversion)
conversion must be one of the following strings indicating how the input x,y should be transformed into the output x,y
x,y = body:convert(x,y,"point_local_to_world")
x,y = body:convert(x,y,"point_world_to_local")
x,y = body:convert(x,y,"vector_local_to_world")
x,y = body:convert(x,y,"vector_world_to_local")
x,y = body:convert(x,y,"point_local_to_velocity")
x,y = body:convert(x,y,"point_world_to_velocity")
convert x,y between various spaces.