Creative Technology Almanac

AR Multiplayer Objects

Github

https://github.com/labatrockwell/xr-research/blob/AR/Multi_User_Demo/Assets/Scenes/AR/Photon/Lobby/Lobby%20Cube%20Changer.unity

Prerequisites

  1. Network Manager New Script - returns true when the room is joined
  2. Networked Image Anchor Script - hides the object container till the image is found

Function

Refer to this project for

  1. instantiating multiplayer objects
  2. syncing characteristics across multiplayer objects

This sketch automatically spawns 10 cubes randomly around the image anchor. When you click on a cube it changes color for all users. The host can hit refresh to respawn cubes.

Details

Instantiation

refer to Photon Initialisation for more details

This code (from Networked Image Anchor.cs)checks for the player that is the MasterClient (host) and instantiates the cube across the network. i.e., one player creates the cubes for all other players as well.

private void Update()  
{  
    if (_networkManagerScript._roomJoined == true && _cubeDrawn == false)  
    {        
	    if (PhotonNetwork.IsMasterClient)  
        {            
	        for (int i = 0; i < 10; i++)  
            {                
	            GameObject cube = PhotonNetwork.Instantiate(Path.Combine("Photon Prefabs", "Sync Color Cube"), targetRandomPosition , Quaternion.identity, 0);  
            }            
            _cubeDrawn = true;  
        }    
	}
}

ADD VIDEO

Color Changing

The cubes have the Networked Colour Changer.cs script attached. When you click a cube, it changes the color and using PunRPC, sends the new values to all other players. The cube color then updates across other players as well.

private void colorCalls()  
{  
    // Change the color locally  
    Color randomColor = GenerateRandomColor(_renderer.material.color);  
    ChangeColor(randomColor);  
    
    // Send color update to other clients (if owner)  
    _photonView = GetComponent<PhotonView>();  
    _photonView.RPC("ChangeColorOnAllClients", RpcTarget.AllBuffered, randomColor.r, randomColor.g, randomColor.b);  
}

The above code shows how a random color is generated and sent to all other clients as its rgb values to all other players. GenerateRandomColor(), ChangeColor(), ChangeColorOnAllClients() are user-defined functions.

Image Anchor

Players’ views are synced by dropping an anchor where the image is. In this example (found in Networked Image Anchor.cs), the container for the cube inherits the same position and rotation of the image anchor. Thus ensuring the cubes spawn at the anchor.

foreach (var trackedImage in trackedImageManager.trackables)  
{  
    if (trackedImage.trackingState == TrackingState.Tracking)  
    {        
	    // Set the position and rotation to match the tracked image  
        parentContainer.transform.position = trackedImage.transform.position;  
        parentContainer.transform.rotation = trackedImage.transform.rotation;  
        _anchorFound = true;  
        InstantiateObjectAtParent();  
        break; // Use the first tracked image found  
    }  
}

In the image below, ‘Drama’ book is the anchor (indicated by a brown quad). As you can see, the anchor is not in the same spot in both images. So there is a slight discrepancy between the location of cubes for both.

Next Steps

  1. Use local cloud anchors as a way of ensuring more accurate colocation

Graph View