Thinking about doing a LDCad 1.7 version

[N. W. Perry]

I realized if you assume all selection points are on a plane, you can drop the setX/setY lines and calculate the plane normal instead of using a static x vector

Code:

function onRun()

  local sel=ldc.selection()
  if sel:getRefCount()<3 then
    return
  end

  local a=sel:getRef(1):getPos()
  local b=sel:getRef(2):getPos()
  local c=sel:getRef(3):getPos()

  local ba=a-b
  local bc=c-b

  local n=bc:getCross(ba)
  n:normalize()

  local bb1=n:getSignedAngle(ba, bc)
  local bb2=math.deg(math.acos(bc:getLength()/ba:getLength()))

  local angle=-(bb1-bb2)
  ldc.setClipboardText(angle)

  ldc.dialog.runMessage(angle)
end

neg y makes it somewhat confusing but i think this should work in any orientation, not tested though.

This version got me close, but not quite: