Altitude Script

[wraith70]

I'm trying to write a script to display the altitude of an aircraft.

Here is what I have so far:

 

local Unit = {}
local id = Unit.getByName('UH1H')
local pos = id:getPosition()
local distance = sqrt((pos.p.x - zonepos.x)^2 + (pos.p.z - zonepos.z)^2) 
   pos2d.x = pos.p.x      --convert Vec3 to Vec2
   pos2d.y = pos.p.z
   landheight = land.getHeight(pos2d)   -- get land height at aircraft location

local _altitude = pos.p.y - landheight

local _string = 'Altitude: ' .. _altitude		 
trigger.action.outTextForGroup(1, _string, 30, false)

When I try it in game and in a LUA decoder, I pretty much get the same result:input:2: attempt to call a nil value (field 'getByName')

 

What can I be doing wrong here?

TIA

[funkyfranky]

Delete the first line.

[wraith70]

When I delete the first line, I get this:

input:1: attempt to index a nil value (global 'Unit')

 

Actually made it worse.

[Hardcard]

@wraith70

 

It definitely made it better, but there are other problems.

 

Is there an existing UNIT called "UH1H" when the script runs? (It must be the PILOT name)

 

If there isn't, you'll get that error.

 

Also, as a general rule, refrain from giving variables the exact same names of DCS classes and common parameters, otherwise you'll have problems all the time.

(Avoid names like Unit, Group, pos, id, etc.)

 

 

As for getting the unit's altitude, do this:

 

local Huey = Unit.getByName('UH1H') [color="Blue"]-- A unit called [i][b]UH1H[/b][/i] (PILOT name) must exist when this runs, otherwise it'll error[/color]
local Huey_Altitude_MSL = Huey:getPoint().y [color="blue"]-- Altitude MSL, in meters[/color]

[color="Blue"]-- Now, if you also want to know the huey's altitude from ground, do this:[/color]

local Huey_Vec3 = Huey:getPoint()
local Huey_Land_Height = land.getHeight({x = Huey_Vec3.x , y = Huey_Vec3.z})

local Huey_Altitude_Ground = Huey_Altitude_MSL - Huey_Land_Height  [color="blue"]-- Altitude from ground in meters[/color]

Edited January 2, 2020 by Hardcard

[wraith70]

@Hardcard

 

Thanks for your input. I did not have the pilot name, so I fixed that, copied verbatim what you posted above, and pasted in a DO SCRIPT and I still get the message:

attempt to index a nil value (global 'Unit') on the first line.

[Hardcard]

@wraith70

 

Works for me, you're doing something wrong.

 

Post your mission file, we'll see what the problem is

[wraith70]

@Hardcard

 

I made a typo. It works great. Thanks for your help.

[wraith70]

Ok,

So I want to take this one step further. Calling the code from a function in a separate LUA file. Here is the function in MissionFunctions.lua:

 

function AGL(pilot_name,unit_of_measure)

--[[
Return
	Aircraft AGL altitude in Meters or Feet
Arguments
	pilot_name = Name of Pilot/Unit in ME
	unit_of_measure = Meters or Feet
]]--

local Huey = Unit.getByName(pilot_name)
local Huey_Altitude_MSL = Huey:getPoint().y -- Altitude MSL, in meters

-- Huey's altitude from ground
local Huey_Vec3 = Huey:getPoint()
local Huey_Land_Height = land.getHeight({x = Huey_Vec3.x , y = Huey_Vec3.z})

-- Altitude from ground in meters
local Huey_Altitude_Ground = Huey_Altitude_MSL - Huey_Land_Height  

--AGL in Meters
local Huey_AGL_Meters = mist.utils.round(Huey_Altitude_Ground , 0) --Round to 0 decimal places

--Convert AGL from Meters to Feet
local Huey_AGL_Feet = mist.utils.round(Huey_Altitude_Ground * 3.28084, 0) --Round to 0 decimal places

if unit_of_measure == meters then 
	return Huey_AGL_Meters
end
if unit_of_measure == feet then 
	return Huey_AGL_Feet
end
end

 

Here is how I'm calling from DO SCRIPT in ME:

 

local _string = AGL('Pilot# 001', 'feet')
trigger.action.outTextForGroup(1, _string, 30, false)

 

I get a error about attempt to load a NIL value again. This must be a scope thing.

 

Attached is a mission file.

 

TIA

MissionFunctions.lua

Altitude Test with Function.miz

Edited January 4, 2020 by wraith70

[Hardcard]

@wraith70

 

Units of measure are passed as strings, not variables, the if conditions in your function should reflect this.

Also, you don't need MIST (or MOOSE) to round up values, standard Lua math.floor() is all you need.

 

Here's a corrected version of your script (haven't tested it, but I don't see why it shouldn't work):

 

function AGL(pilot_name,unit_of_measure)

[color="Blue"]--[[
 Return
   Aircraft AGL altitude in Meters or Feet
 Arguments
   pilot_name = Name of Pilot/Unit in ME
   unit_of_measure = Meters or Feet
]]--[/color]
 
 local Huey = Unit.getByName(pilot_name)
 local Huey_Altitude_MSL = Huey:getPoint().y -- Altitude MSL, in meters

 -- Huey's altitude from ground
 local Huey_Vec3 = Huey:getPoint()
 local Huey_Land_Height = land.getHeight({x = Huey_Vec3.x , y = Huey_Vec3.z})

 -- Altitude from ground in meters
 local Huey_Altitude_Ground = Huey_Altitude_MSL - Huey_Land_Height  

 --AGL in Meters         
 local Huey_AGL_Meters = math.floor(Huey_Altitude_Ground , 0) [color="blue"]--Round to 0 decimal places[/color]

 --Convert AGL from Meters to Feet
 local Huey_AGL_Feet = math.floor(Huey_Altitude_Ground * 3.28084 , 0) [color="blue"]--Round to 0 decimal places[/color]
 
 if unit_of_measure == 'meters' then  [color="Blue"]-- Notice the quotation marks[/color] 
   return Huey_AGL_Meters
 end
 if unit_of_measure == 'feet' then [color="Blue"]-- Notice the quotation marks[/color] 
   return Huey_AGL_Feet
 end
end

Edited January 4, 2020 by Hardcard

[wraith70]

Thanks for your response. I've incorporated the changes you suggested. I still get the attached error message.

The code works fine until i call it in a function.

 

Attached is also the updated mission file.

 

Thanks

Altitude Test with Function.miz

[Hardcard]

@wraith70

 

There are two problems in your mission

 

• Incorrect pilot name in the function call, you wrote "Pilot# 001" instead of "Pilot #001"
   
   
  
• MissionFunctions.lua needs more than 1 second to be fully loaded. If you start calling functions just one second after loading it, you'll get errors.
  As a rule of thumb, load your function libraries at mission start (no conditions) and give them a few seconds to load, before you start calling stuff from other scripts.
  

Edited January 4, 2020 by Hardcard

[wraith70]

Pilot #001 makes it work..go figure. I've loaded the function library at mission start. It's all working now. Thanks again Hardcard