[FiveM] calculate visualize dot product and angle between player and closest vehicle

dot_and_angle.lua

local entityEnumerator = {
  __gc = function(enum)
    if enum.destructor and enum.handle then
      enum.destructor(enum.handle)
    end
    enum.destructor = nil
    enum.handle = nil
  end
}

local function EnumerateEntities(initFunc, moveFunc, disposeFunc)
  return coroutine.wrap(function()
    local iter, id = initFunc()
    if not id or id == 0 then
      disposeFunc(iter)
      return
    end
    
    local enum = {handle = iter, destructor = disposeFunc}
    setmetatable(enum, entityEnumerator)
    
    local next = true
    repeat
      coroutine.yield(id)
      next, id = moveFunc(iter)
    until not next
    
    enum.destructor, enum.handle = nil, nil
    disposeFunc(iter)
  end)
end

function EnumerateObjects()
  return EnumerateEntities(FindFirstObject, FindNextObject, EndFindObject)
end

function EnumeratePeds()
  return EnumerateEntities(FindFirstPed, FindNextPed, EndFindPed)
end

function EnumerateVehicles()
  return EnumerateEntities(FindFirstVehicle, FindNextVehicle, EndFindVehicle)
end

function EnumeratePickups()
  return EnumerateEntities(FindFirstPickup, FindNextPickup, EndFindPickup)
end

function Smallest(tbl, getter)
  if #tbl == 0 then return nil end
  local ele = tbl[1]
  local smallest = getter(ele)
  for i = 2, #tbl do
    local val = getter(tbl[i])
    if val < smallest then
      smallest = val
      ele = tbl[i]
    end
  end
  return ele
end

function GetAllVehicles()
  local ret = {}
  for veh in EnumerateVehicles() do
    table.insert(ret, veh)
  end
  return ret
end

local function DrawStr(text, r, g, b, x, y, width, height) 
  SetTextColour(r, g, b, 255)
  SetTextScale(width, height)
  SetTextFont(0)
  SetTextWrap(0.0, 1.0)
  SetTextCentre(true)
  SetTextDropshadow(0, 0, 0, 0, 0)
  SetTextEdge(1, 0, 0, 0, 205)
  SetTextEntry("STRING")
  AddTextComponentString(text)
  DrawText(x, y)
end
local function radToDeg(r)
  return r * 180 / math.pi
end
local function atan2(y, x)
  if x > 0 then
    return math.atan(y/x)
  elseif x < 0 and y >= 0 then
    return math.atan(y/x) + math.pi
  elseif x < 0 and y < 0 then
    return math.atan(y/x) - math.pi
  elseif x == 0 and y > 0 then
    return math.pi/2
  elseif x == 0 and y < 0 then
    return math.pi/-2
  else
    return nil
  end
end
Citizen.CreateThread(function() 
  while true do
    local myCoords = GetEntityCoords(GetPlayerPed(-1))
    local veh = Smallest(GetAllVehicles(), function(veh) return #(GetEntityCoords(veh) - myCoords) end)
    if veh ~= nil then
      local heading = GetEntityHeading(veh)
      local vehPos = GetEntityCoords(veh)
      local vehForward = GetEntityForwardVector(veh)
      vehForward = vec3(vehForward.x, vehForward.y, 0)
      
      local vehToPlr = norm(myCoords - vehPos)
      vehToPlr = vec3(vehToPlr.x, vehToPlr.y, 0)
      
      DrawLine(vehPos, vehPos + (vehForward*5), 255,0,0,255)
      DrawLine(vehPos, vehPos + (vehToPlr*5), 0,255,0,255)
      
      local angle = atan2(cross(vehForward, vehToPlr).z, dot(vehForward, vehToPlr))
      
      DrawStr(("Angle: %.0f"):format(radToDeg(angle)), 255, 0, 0, .5, .5, .5, .5)
      DrawStr(("Dot:   %.2f"):format(dot(vehForward, vehToPlr)), 255, 0, 0, .5, .55, .5, .5)
    end    
    Wait(0)
  end
end)