Instantiated object not positioned correctly when using World Anchors

bfichter

I will try to explain this the best I can.

I want to instantiate and position a GameObject at a specific location relative to an existing GameObject when using WorldAnchor. Both GameObjects should be under the same parent.

Here's what I am doing now (which isn't working):
I have a GameObject (HologramCollection) I am using as a parent for a collection of models.
I have developed controls to finely position this HologramCollection. (Basically buttons to move .01m a click.)
I add a WorldAnchor component to this HologramCollection upon start.
Each time I move the HologramCollection I am destroying then adding the WorldAnchor again:

DestroyImmediate(hologram.GetComponent<WorldAnchor>());
hologram.transform.position = newLocation;
anchor = hologram.AddComponent<WorldAnchor>();

This all works fine.

My application receives coordinates externally (lat, lon).
When I get the new coordinate, I convert it to the local space of one of the children models of the HologramCollection.

I convert the local position to the Unity world position using:

terrainModel.transform.TransformPoint(new Vector3(x, y, z))

I instantiate an object at that position.

This all works fine and the object is placed correctly when I don't create or set a WorldAnchor.

As soon as I use world anchors, the instantiated object is not positioned correctly. Furthermore if I move the Hololens a lot, the position is different each time.

I am wondering if the position of the WorldAnchor should be accounted for or if I am missing something else.

bfichter

Any thoughts?

timg

Hi @bfichter

I've been playing around with this and haven't been able to reproduce what you are describing; I get the same behavior with and without WorldAnchors.

How are you Instantiating your new object?

I created a scene with two cubes (red and blue) with red on the left and blue on the right. Both cubes are children of the same HologramCollection GameObject. When I move my collection, I remove the WorldAnchor

public void MoveCollection()
{
    isMoving = true;
    if (anchor)
    {
        DestroyImmediate(anchor);
    }
    SpatialMappingManager.Instance.DrawVisualMeshes = true;
}

When I stop moving my collection, I create and add a new WorldAnchor

public void StopMoving()
{
    isMoving = false;
    anchor = gameObject.AddComponent<WorldAnchor>();
    SpatialMappingManager.Instance.DrawVisualMeshes = false;
}

When I add a new object (green cube), I position it to the left of the red cube. Successively added green cubes are positioned to the left of previously added green cubes.

float xOffset = 0.0f;
public void CreateObject()
{
    Vector3 newLocation = leftCube.transform.TransformPoint(
        xOffset -= 1.0f,
        leftCube.transform.localPosition.y,
        leftCube.transform.localPosition.z);
    Instantiate(prefab, newLocation, transform.rotation, transform);
}

All code is in the same script which is attached to my HologramCollection object.

Regardless of where I position the HologramPosition, the green cubes always appear where expected (in a line to the left of the red cube). I see the same behavior with and without adding the WorldAnchor (in StopMoving() above).

One additional note, I'm using Unity 5.5.0b7