Question

I am using unity and vuforia for Android to create an AR app (project). I have a 3d text and i want to change it’s position corresponding to user’s location.

Right now, i can get his location and updates and i can show it on a Gui label using OnGUI function.

The 3d Text is a prefab so do i have to instantiate it everytime the user gets to a new location?

The 3d Text should appear only once (depending his current location). That means, i have to destroy first, previous instantiated texts or will it be overriden?

Finally, where should i write the instantiation code? I mean, on the Update() function? Start()? so to be run only when location changes and not all the time.

I am currently getting familiar with Unity and i am trying to figure out how it works.
Ask me if you would like more information.

Thank you in advance for your time and answers!

Answer 1

Depends on your project setup and there are probably other ways to do this but I would suggest hiding the 3D Text via the mesh renderer. In your code you want to check in the update function if there`s been a change in the location since the last update. How you go about this is by creating two variables: one for the users current position and one for the position at the previous update call. So the secret here is two functions: Update and LateUpdate.

Here`s an example

#pragma strict
@script ExecuteInEditMode;

var curPos : Vector3;
var lastPos : Vector3;
var timeToWait : float = 2.0;
var shwoing : boolean;

function Start()
{
    ShowText(false);
}

function Update()
{
    // check if our current position is the same as our last position
    if(lastPos != curPos && !showing)
    {
        ShowText(true);     // Show the 3d text
    }

    if(lastPos == curPos && showing)
    {
        ShowText(false);    // Don't show the text
    }
}

function LateUpdate()
{
    lastPos = curPos;   // change our last Positon to our current position
}

function ShowText(state : boolean)
{
    renderer.enabled = state;    // enable or disable the renderer
    showing = true;              // variable to tell to keep showing text
    yield WaitForSeconds(timeToWait);   // wait a few seconds before changing the state
    showing = false;             // tell update to not show text
}

Doing things this way you don’t have to face the headache of cleaning up your scene as you only have once instance of the 3DText to deal with. I hope this helps… it might need a lil bit of work but i gotta run now. Lemme know if you need me to explain a lil more.