We have decided to phase out the Mixed Reality Forums over the next few months in favor of other ways to connect with us.
The first way we want to connect with you is our mixed reality developer program, which you can sign up for at https://aka.ms/IWantMR.
The plan between now and the beginning of May is to clean up old, unanswered questions that are no longer relevant. The forums will remain open and usable.
On May 1st we will be locking the forums to new posts and replies. They will remain available for another three months for the purposes of searching them, and then they will be closed altogether on August 1st.
So, where does that leave our awesome community to ask questions? Well, there are a few places we want to engage with you. For technical questions, please use Stack Overflow, and tag your questions using either hololens or windows-mixed-reality. If you want to join in discussions, please do so in the HoloDevelopers Slack, which you can join by going to https://aka.ms/holodevelopers. And always feel free to hit us up on Twitter @MxdRealityDev.
Building/Packaging Unity Immersive Apps
I've been working with Unity for a couple years now, but Mixed Reality was my first time building a Universal Windows Platform / Windows Store application using it. I had some trouble, and it took some trial and error, but I did finally get it to work, so I thought I'd share some of the details I found, in hopes of making this easier for others.
First, in Unity (2017.2.0b5 (or later), of course), go to File, Build Settings. Under Platform, choose Universal Windows Platform. For target device, choose "HoloLens" (note, I believe you should be able to use "Any" as well, but I wasn't able to get this to work). Build Type should be D3D, and for everything else, I believe the defaults are fine.
Now, when you press "Build", you won't actually be creating your executable, instead, you'll be making a Visual Studio project that you'll need to open that can build your executable. Go to the directory you picked for the build, and open the solution file found there.
Change the configuration to x64, and optionally, Release (or Master - that's the final / stripped version you can upload to the store), and make sure it builds. Note, you may have to install additional components of Visual Studio in order to make the projects in this solution load correctly.
Once the build is done, just going to the directory and running the executable will not work - you'll get two error messages about missing DLLs. The solution I found here (feel free to comment if you know of others!) is to build the package for your application.
In Solution Explorer, right click your project name (should have "(Universal Windows)" after it) and go to store, and pick "Create App Packages". Choose "No" to build packages to upload to the Windows Store (unless that's what you want and you're already a registered developer ($20 for an individual, $100 for a company, free if you're a MSDN subscriber)). Then continue on - the defaults are fine, though I generally leave only x64 checked for architecture.
The next window that appears when it finishes has a link to output location. Double clicking on your app will install it. If you get an error about a security certificate, go back to the folder and use the "Add-AppDevPackage" Windows PowerShell script that is in the directory. Right click, "Run with PowerShell" and it will take care of getting security certificate setup (with some prompting from you).
Once installed, you can go to the mixed reality portal and find your application in the list of all apps. Place it, and then select it to start it. If all goes well, your Unity project will start up and be running!
Again, I'm not an expert at this but - I hope this guide makes the process a little easier for people like me who have worked with Unity for awhile, but are inexperienced with this new build workflow. Good Luck.