pickUpDistance = 10000

    local x, y, z = GetCameraPositionX(0) , GetCameraPositionY(0) , GetCameraPositionZ(0)
 
    local rayX, rayY, rayZ =  0, 0, pickUpDistance
 
    local paX, paY, paZ = math.rad(GetCameraAngleX(0)), math.rad(GetCameraAngleY(0)), math.rad(GetCameraAngleZ(0))	
					   
    rayX, rayY, rayZ = Rotate3D(rayX, rayY, rayZ, paX, paY, paZ)
 
    local Pobj = (IntersectAll(x, y, z, x + rayX, y + rayY, z + rayZ, 0))  

NEAR = 100
FAR = 4000

WIDTH            = GetDeviceWidth() 
HEIGHT           = GetDeviceHeight() 
WIDTH_DIV_2      = (WIDTH*0.5)
HEIGHT_DIV_2     = (HEIGHT*0.5)
ASPECT           =  1.3333

local dx=math.tan(g_PlayerFOV*0.5)*(g_MouseX/WIDTH_DIV_2-1.0)/ASPECT;
local dy=math.tan(g_PlayerFOV*0.5)*(1.0-g_MouseY/HEIGHT_DIV_2);

local p1x, p1y, p1z = dx*NEAR,dy*NEAR,NEAR
local p2x, p2y, p2z = dx*FAR,dy*FAR,FAR

p1 = MATRIX{p1x,p1y,p1z}
p2 = MATRIX{p2x,p2y,p2z}

pm = projectionMatrix(g_PlayerFOV,ASPECT, NEAR, FAR)
im = pm --MATRIX.invert(pm) --trying to do invert gives an error

--https://www.varsitytutors.com/hotmath/hotmath_help/topics/multiplying-vector-by-a-matrix
p1rx = im[1][1]*p1x + im[1][2]*p1x + im[1][3]*p1x 
p1ry = im[2][1]*p1y + im[2][2]*p1y + im[2][3]*p1y 
p1rz = im[3][1]*p1z + im[3][2]*p1z + im[3][3]*p1z

p2rx = im[1][1]*p2x + im[1][2]*p2x + im[1][3]*p2x 
p2ry = im[2][1]*p2y + im[2][2]*p2y + im[2][3]*p2y 
p2rz = im[3][1]*p2z + im[3][2]*p2z + im[3][3]*p2z

local Pobj = (IntersectAll(p1rx, p1ry, p1rz, p2rx, p2ry, p2rz, 0)) 

MATRIX = assert(loadfile "scriptbank\\lib\\MATRIX.lua")()

--Lua Game Development Cookbook
--http://www.songho.ca/opengl/gl_projectionmatrix.html
function projectionMatrix(fov,aspect,znear,zfar)
	-- xymax variable refers to the coordinate
	-- of the right/bottom clip-pane
	local xymax = znear * math.tan(math.rad(fov/2))
	local ymin = -xymax -- top clip-pane
	local xmin = -xymax -- left clip-pane
	
	local width = xymax - xmin
	local height = xymax - ymin
	local depth = zfar - znear
	
	-- q and qn paramters are use to achieve
	-- perspective correction
	local q = -(zfar + znear) / depth
	local qn = -2 * (zfar * znear) / depth
	
	local w = 2 * znear / width
	w = w / aspect
	local h = 2 * znear / height
	
	-- transposed version of the projection matrix
	return MATRIX({
		{w, 0, 0, 0},
		{0, h, 0, 0},
		{0, 0, q, 0},
		{0, 0, qn, 0}
	})
end

--[[ 
mapcoords.lua
How to determine the map coordinates that are under the screen cursor
A learning script by perelect.
--]]

function mapcoords_init(e)
SetGamePlayerStateCameraFov(42.2)	-- tested at resolution 1366 x 768
end
  
function mapcoords_main(e)
	
	-- Common Camera Variables	 
	local Camera_X   = GetCameraPositionX(0)
	local Camera_Z   = GetCameraPositionZ(0) 
	local Camera_Y   = GetCameraPositionY(0)
	local Camera_T   = GetTerrainHeight( Camera_X , Camera_Z )
	local Camera_TD  = ( Camera_Y - Camera_T )	
	   
	-- Screen Cursor distance from the center of the screen
	if g_MouseX <= 50 then Cursor2D_X = -50 + g_MouseX end
	if g_MouseX >  50 then Cursor2D_X = -50 + g_MouseX end
	if g_MouseY <= 50 then Cursor2D_Y =  50 - g_MouseY end
	if g_MouseY >  50 then Cursor2D_Y =  50 - g_MouseY end
	
	-- 3D Cursor 
	local Cursor3D_X = ( Camera_X + (Cursor2D_X*(Camera_TD * ((( GetDeviceWidth ()/2)/1000)/50))) ); -- Map X position under the screen cursor
	local Cursor3D_Z = ( Camera_Z + (Cursor2D_Y*(Camera_TD * ((( GetDeviceHeight()/2)/1000)/50))) ); -- Map Z position under the screen cursor	
	local Cursor3D_Y = GetTerrainHeight( Cursor3D_X , Cursor3D_Z );	
	
	-- Set the camera
	SetCameraOverride ( 3 )			 
	SetCameraAngle ( 0 , 90 , 0 , 0 )
	SetCameraPosition ( 0 , 25000 , 3600 , 25000 )
	
	-- Display values	
	TextColor(10,10,3,"MAP COORDINATES",255,255,255) 
	TextColor(10,13,3,"Cursor3D_X: "..math.floor(Cursor3D_X),255,255,255)   
	TextColor(10,16,3,"Cursor3D_Z: "..math.floor(Cursor3D_Z),255,255,255) 
	TextColor(10,19,3,"Cursor3D_Y: "..math.floor(Cursor3D_Y),255,255,255) 
	TextColor(10,25,3,"SCREEN COORDINATES",255,255,255)
	TextColor(10,28,3,"Mouse X:    "..math.floor(g_MouseX),255,255,255)  
	TextColor(10,31,3,"Mouse Y:    "..math.floor(g_MouseY),255,255,255) 
  
end