FIRST OF ALL - WHAT IS PHOTON ENGINE?

Some of us have the misconception that photon is similar a version of Unity, but for multiplayer games. It's not. It is a service in the cloud that host your application-server side logic so you don't have to deal with networking heavy lift issues such as synchronization, timeouts, packet management, etc.

Unity is a game engine responsible for rendering, physics, update animations and manage user interaction, in other words the client side logic. Every time you update a game object position, activate a button or destroy any element in the scene you need to send that information over the net to the server, and the server synchronizes the information across all the clients. This is what Photon does.

THE BEST OF ALL IT'S FREE AND YOU CAN USE AS MANY APPS AS YOU WANT IN MULTIPLAYER MODE. THE ONLY LIMITATION IS THE NUMBER OF PLAYERS CONNECTED TO THE SERVER. 

Make sure to watch all the videos before jumping to implementation. The creator corrects himself A LOT from one video to the other. So you might find yourself in issues that he solves at the end of the video or in part 3. 

Also, he uses Unity 2019 and the latest LTR is 2021. Some things have changed since then:

• The XR tool it main class is called XROrigin. 

• Ignore the last part of Part 1. His implementation only support local transformations and you need world transformations.

THIS IS VERY IMPORTANT

Keep the Photon View transform component in the Root game object. If you need to update local transformations ( specific parts of the body ) then add another Photon View transform to those part as well. If you dont do this, the other clients wont be able to see the other players move in multiplayer mode.  

In the video tutorials, he tries to clean/organize his component dependency as much as he could, moving and removing photon components from multiple entities. I also did it, but it broke my simulation a day after the presentation and I couldnt solve the issue on time. 

Just add the Photon View transform to every game object you need to synchronize online.

Unfortunately, there is no easy way to test it. In the VR application case you need whether multiple HMDs. But if you only have one HMD, you can run an instance of your application from your computer and run another instance in your HMD. However, because your hardware limitations, only one instance is able to display in the VR headset and have access to the controllers input.

Test locally using Unity (Windows)

• First, Build you application for PC. Go to File -> Build settings -> select window platform and add the scenes. Select the folder where the application will be exported.

• Run the application in Unity using the "Play" Button 

• Now, go to the folder where the built application is located. Open the applications and the HMD will switch to the unity ran instance to the built instance. The unity instance still runs but it loses all the input from the headset and the controllers.

• If you check the Project hierarchy in Unity, you will see multiple players in the scene.  This is also explained in the videos, but the creator misses an important point. If you select any of the networking players you can see their properties, such as transformations, physics and collision properties. That way you can debug their positions and user interactions in real time.