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modelToWorld used with worldToScreen = bad position given
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When we use the modelToWorld combined with worldToScreen in moving vehicles the position given its not the correct one.
Its caused by a velocity error acting with worldToScreen causing for example:

If our modelToWorld is at [0,2,0] // In a AH-9 helicopter
and we use worldToScreen to transform the coordinates into x,y positions and it give us 1,1... when the vehicle starts to move it changes to 1.5,1.5 or 2,2 and not in 1,1 then we cant use them.

This video is not the bug that im having but it describes how the worldToScreen x,y positions are moving into a bad one.


Operating System
Windows 7
Operating System Version
Game Physics
Steps To Reproduce

You can create an script like this one that is an interaction cockpit system.

1. Create a sqf file and name it to pfh_click.sqf

Put this in:

//if the player isn't in a helicopter then we don't run this
if(vehicle player iskindof  "Helicopter") then
_heli = vehicle player;
if(isNil "button_clicked") then {button_clicked = 0;}; //keeps our key from constantly having an effect - that is, press it once and it won't do anything again until released and pressed again

_controlpos = worldToScreen (_heli modelToWorldVisual [0,2,0]);

if(count _controlpos < 2) then {_controlpos = [-100,-100];}; //if the point is outside of our FOV then set it to something ridiculous
_hinttext = "No Action"; //basic hint to indicate what we're looking at

player sidechat format ["%1",_controlpos]; //debugging - shows position of a control on screen coordinates; the closer to 0.5,0.5, the closer it is to the center of the screen

if(_controlpos distance [0.5,0.5] < 0.025) then {_hinttext = "Toggle Engine";}; //change hint to engine on

if(!(_hinttext == "")) then {hintsilent format ["%1",_hinttext];}; //set our hint text

if(_hinttext == "No Action") exitwith {}; //if no action available then we don't need to do anything so quit

//check to see if our action is within the right parameters and that the key has been pressed, then do something
if(inputaction "User20" > 0.1 && button_clicked == 0 && _controlpos distance [0.5,0.5] < 0.01) then
	if(isengineon _heli) then
		player action ["EngineOff", _heli];
	} else {
		player action ["EngineOn", _heli];
button_clicked = 1;

//clear our key press if it's not being pressed
if(inputaction "User20" < 0.5) then
button_clicked = 0;

What it does, it takes a model position to a world one then it takes the world position to screen coordinates, so when aim with your screen (0.5,0.5) at that point it hint you "Toggle engine" and if you press the "Custom key 20" it starts the engine.
But if you arent aiming at the point it hint you "No action"

2. Spawn an AH-9 helicopter

3. Put this in the debug console (ESC) and execute it

my_clickaction = compile preprocessFileLineNumbers "pfh_click.sqf";  ["my_clickid", "onEachFrame", "my_clickaction"] call BIS_fnc_addStackedEventHandler;
Additional Information

Its good to have this working correctly so people can create interaction systems

Event Timeline