Develop Reference

Xamarin ARcore change position of 3D object

I am trying to implement ARcore with Xamarin and want to set a 3D object in a specific geolocation (like in pokemongo). I tried to go through this sample that I found in this forum: https://blog.xamarin.com/augmented-reality-xamarin-android-arcore/ but it seems that I can't change the position of the 3d object and it is set according to the tap gesture only on a plane.
Is there a way to place an object and track it? I did manage to do that with ARkit, but until now no success for the ARcore Android.
Any ideas would be helpful.

It looks like the Xamarin wrapper for ARCore simply wraps OpenGL. As a result, drawing the object requires setting multiple matrices (Model, View and Projection) matrices:
objectRenderer.UpdateModelMatrix(anchorMatrix, scaleFactor);
objectRenderer.Draw(viewMatrix, projectionMatrix, lightIntensity);
If you simply remove this from within the foreach (var planeAttachment in planeAttachments) {
loop, then you can set the anchorMatrix (a.k.a. the modelMatrix) to a fixed/hardcoded translation then it'll fix itself relative to the camera.
Here's a decent article on View matrices: https://www.3dgep.com/understanding-the-view-matrix/#The_View_Matrix
-- Begin Shameless Plug --
However, if you are open to trying new platforms, my team has built a cross-platform React-Native library for AR/VR development (Viro React): https://viromedia.com/viroreact/
If you're more familiar with SceneKit on iOS, we have built an analogous solution on Android w/ AR/VR support (ViroCore): https://viromedia.com/virocore/
Either solution would allow you to skip over the intricacies of OpenGL and simply position your objects/models with relative ease.
ie.
Placing your model 1 meter in front of you would be as simple as (in Viro React):
<Viro3dObject source={require("./res/model.obj")} position={[0,0,-1]} type="OBJ" />

Changing GameObject Position with Unity and ARToolkit

I'm building an Augmented Reality app with Unity and ARToolkit for Android. I have multiple GameObjects on screen that are children of my marker. Works well. I then created a very simple script to move one of the objects and I attached the script to the game object. It looks like:
void Update()
{
Vector3 currentPos = transform.position;
transform.position = new Vector3(currentPos.x + (.01f * xDirection * xSpeed), currentPos.y + (.01f * yDirection * ySpeed), currentPos.z);
}
The rest of the script does nothing other than alter the value of the direction and speed variables. It works and goes in the directions that I expect, however the object shrinks in size visually. Possible it's just lower on the z axis so it appears smaller, or possible scaling is getting affected. I think it may be related to the movement of the phone up and down while looking at the marker.
I suppose I have to move GameObjects in a different manner than normal when using ARToolkit. What's the proper way?
Thanks

I've no connection with ARToolkit by try checking out their Coordinate System

Recenter or Reorient view with Cardboard SDK on Unity

With Unity, the CardboardHead script is added to the main camera and that handles everything quite nicely, but I need to be able to "recenter" the view on demand and the only option I see so far is to rorate the entire scene and it seems like this is something the would address first-hand and I can't find anything in the docs.
With Oculus Mobile SDK (GearVR), it would be OVRCamera.ResetCameraPositionOrientation(Vector3.one, Vector3.zero, Vector3.up, Vector3.zero); though they handle it nicely each time the viewer is put on so it's rarely needed there.

There's a "target" parameter on the CardboardHead that lets you use to another gameobject as a reference for rotation. Or you can use a dummy parent gameobject. Either way, when you want to recenter, you set this reference object's rotation so that the CardboardHead is now pointing forward. Add this function to an script on the CardboardHead (or just add it into that script):
public void Recenter() {
Transform reference = target != null ? target : transform.parent;
if (reference != null) {
reference.rotation = Quaternion.Inverse(transform.rotation) * reference.rotation;
// next line is optional -- try it with and without
reference.rotation = Quaternion.FromToRotation(reference.up, Vector3.up) * reference.rotation;
}
}

Cardboard.SDK.Recenter (); should do the trick.
Recenter orientation Added Recenter() function to Cardboard.SDK, which resets the head tracker so the phone's current heading becomes the forward direction (+Z axis).
Couldn't find the docs for the API/SDK but it's in the release notes for the v0.4.5 Update.

You can rotate the Cardboard Main to point in a certain direction.
This is what worked for me when I wanted the app to start up pointing a certain way. Since the CardboardHead points at Vector3.zero on startup if no target is assigned, I ran a function during Start() for the CardboardMain that would point in the direction I wanted.
Of course, if you're already rotating CardboardMain for some other reason, it may be possible to use this same method by creating a parent of the CardboardHead (child of CardboardMain) and doing the same thing.

This question is a bit old but for Google VR SDK 1.50+ you can do
transform.eulerAngles = new Vector3(newRot.x, newRot.y, newRot.z);
UnityEngine.VR.InputTracking.Recenter();
also, if you don't want to get confused you also need to catch the GvrEditorEmulator instance and Recenter it as well.
#if UNITY_EDITOR
gvrEditorEmulator.Recenter();
#endif
Recentering GvrEditorEmulator though doesn't seem to work very well at the moment but if you disable it you'll see the recentering works for the main camera.

Magnet script for UNITY 3D

I'm working on a Google Cardboard project, right now i have a demo for Android where u can look around in a special scene i build in UNITY 3D, everything is working fine & looking good, but what I really want is:
I want to walk forward when I press the Google Cardboard magnet button.
I found a few script's on the web, but I do not know exactly how to make these scripts work in my UNITY project.
Can anybody help me further with this?

Assuming you are able to read the magnet input correctly. This is how I did an FPS style controller script:
In Unity5 import the asset package Standard Assets/Characters.
Create an instance of RigidBodyFPSController.prefab from that package.
Remove it's child object, "MainCamera"
Import the Google cardboard unitypackage.
Replace the "MainCamera" you removed in step #3 with CardboardMain.prefab
Update or modify a copy of RigidbodyFirstPersonController.cs GetInput() method.
GetInput() with Google Cardboard forward movement fallback:
private Vector2 GetInput()
{
Vector2 input = new Vector2
{
x = Input.GetAxis("Horizontal"),
y = Input.GetAxis("Vertical")
};
// If GetAxis are empty, try alternate input methods.
if (Math.Abs(input.x) + Math.Abs(input.y) < 2 * float.Epsilon)
{
if (IsMoving) //IsMoving is the flag for forward movement. This is the bool that would be toggled by a click of the Google cardboard magnet
{
input = new Vector2(0, 1); // go straight forward by setting positive Vertical
}
}
movementSettings.UpdateDesiredTargetSpeed(input);
return input;
}
Google's SDK only support's detecting a magnet "click". If you want to hold down the magnet to move forward, I recommend using Cardboard Controls+ from the Unity3D Asset Store.

Panning the view of a gameObject instead of the camera in Unity3d?

I'm having a hard time to pan a view of a gameObject in Unity3d. I'm new to scripting and I'm trying to develop an AR (Augmented Reality) application for Android.
I need to have a gameObject (e.g. a model of a floor), from the normal top down view, rendered to a "pseudo" iso view, inclined to 45 degrees. As the gameObject is inclined, I need to have a panning function on its view, utilizing four (4) buttons (for left, right, forward(or up), backward(or down)).
The problem is that, I cannot use any of the known panning script snippets around the forum, as the AR camera has to be static in the scene.
Need to mention that, I need the panning function to be active only at the isometric view, (which I already compute with another script), not on top down view. So there must be no problem with the inclination of the axes of the gameObject, right?
Following, are two mockup images of the states, the gameObject (model floor) is rendered and the script code (from Unity reference), that I'm currently using, which is not very much functional for my needs.
Here is the code snippet, for left movement of the gameObject. I use the same with a change in -, +speed values, for the other movements, but I get it only move up, down, not forth, backwards:
#pragma strict
// The target gameObject.
var target: Transform;
// Speed in units per sec.
var speedLeft: float = -10;
private static var isPanLeft = false;
function FixedUpdate()
{
if(isPanLeft == true)
{
// The step size is equal to speed times frame time.
var step = speedLeft * Time.deltaTime;
// Move model position a step closer to the target.
transform.position = Vector3.MoveTowards(transform.position, target.position, step);
}
}
static function doPanLeft()
{
isPanLeft = !isPanLeft;
}
It would be great, if someone be kind enough to take a look at this post, and make a suggestion on how this functionality can be coded the easiest way, as I'm a newbie?
Furthermore, if a sample code or a tutorial can be provided, it will be appreciated, as I can learn from this, a lot. Thank you all in advance for your time and answers.

If i understand correctly you have a camera with some fixed rotation and position and you have a object you want to move up/down/left/right from the cameras perspective
To rotated an object to a set of angles you simply do
transform.rotation = Quaternion.Euler(45, 45, 45);
Then to move it you use the cameras up/right/forward in worldspace like this to move it up and left
transform.position += camera.transform.up;
transform.position -= camera.transform.right;
If you only have one camera in your scene you can access its transform by Camera.main.transform
An example of how to move it when someone presses the left arrow
if(Input.GetKeyDown(KeyCode.LeftArrow))
{
transform.position -= camera.transform.right;
}