Is there any way to open multiple projects at the same time in two different Unity windows? Whenever I try opening a second instance of Unity, I get the message "Fatal Error! It looks like another Unity instance is running with this project open". I presume this is because Unity automatically loads the most recent project when it's opened. Is there any way to disable this, or any other way to do what I want?
Answer by jashan
Nov 29, 2009 at 10:52 AM
You can open multiple different projects with Unity at the same time; however, opening the same project twice could ruin the project in previous versions and so I guess they've added a check to prevent this (seems like that check only is implemented for Windows because I can't reproduce this here on my Mac).
If you want to open "the same" project twice, you can make a copy of the project, which can be very useful for debugging networked games on a single machine. If you're using Asset Server or another version control system, it may be a good idea to keep both versions under version control - that way, you can make changes on both "sides" and still keep everything in sync pretty conveniently.
In the Unity Preferences, there's a checkbox "Show Project Wizard at Startup" - if that's checked, Unity opens that wizard instead of opening the previously opened project; so that should solve the issue for you. On Mac OS X, you can also cmd+click (press the cmd/Apple key and click) the app-icon to achieve the same effect without changing this setting. Might work under Windows as well (probably would be ctrl+click but if that doesn't work, I'd try shift+click and alt+click as well) - but I can't try that because I don't have Unity on a Windows machine ATM, so I'm not sure.
On Mac OS X, when you double click the app-icon while the application is already running, you simply "focus" the opened instance. So you need a little trick to open two instances of Unity (Windows handles this differently, so it's easier to open multiple instances there - just double click twice and you got two instances running):
Either right click on the app-icon in the Finder, and select "Show Package contents", the browse to "Contents/MacOS" and double click "Unity" (which has a console Icon there). That does in fact open a console and you got your second instance. Which kind of leads to the second way of doing this:
You can also open Unity directly from the console and this also allows you to give the project path; so you could create a couple of scripts for directly opening a couple of different projects (that's what I did for working on my client-server based game):
/Applications/Unity/Unity.app/Contents/MacOS/Unity -projectPath "/path/to/your/projectA"
If you put that into a file (e.g. startProjectA.sh) and make it executable (chmod a+x startProjectA.sh), you're all set ;-) ... ah, simplest way to create such a script (IMHO): in the console, type vim startProjectA.sh, then type "i" (to get into insert mode), type the script, when you're done, hit "esc", then :wq (: lets you type commands, w is write, q is quit). I think vim is pretty cool but it takes a moment to get used to it.
there is no CMD+click equivalent in windows.
this is the exact text from unity's manual
You can launch Unity two times on the same machine, and open different projects in each. On Windows, this can be done by just launching another Unity instance and opening the project from the project wizard. On Mac OS X, multiple Unity instances can be opened from the terminal, and a -projectPath argument can be specified:
in windows you should just go to prefs and ...
Awesome, thanks! =)
I knew there had to be a way to disable automatically opening a project on startup, just couldn't figure out what option it was =P
"In the Unity Preferences, there's a checkbox "Show Project Wizard at Startup" - if that's checked, Unity opens that wizard instead of opening the previously opened project; so that should solve the issue for you." is the solution Windows Vista 64bit
This works like charm in MacOS...
I've activated the "Show Project Wizard at Startup" and removed the option "-projectPath". This way I can choose the project I want.
I know this is fairly old now; but just a little extra bit of information, Jashan is correct about the alt key under windows. But in order to do it: - launch unity, and press and hold the ALT key down while the splash screen is up. It will load the project wizard instead of the last project. (essentially the same action as preventing Auto-Run when you insert a CD/DVD into your machine, under windows)
Answer by ChiefSpruce
Sep 27, 2010 at 08:52 PM
From the terminal in Mac OS:
open -na Unity
Although I'd recommend having the Preferences -> Show Project Wizard at Startup is checked as discussed above if using this technique.
-n, --new Open a new instance of the application even if one is already running
-a Opens with the specified application
Upvoted, as this works for Unity5 as well ... Cheers
Much easier than the "Best Answer"
Answer by futurefreak
Mar 18, 2010 at 12:15 PM
If your Edit - > Preferences - >Show project Wizard at Startup is unchecked - then it automatically tries to load the last project you worked on. Check this option and you can load in multiple projects by running more than one instance of Unity (I'm using Windows 2.6.1)
Perfect! thank you!
Windows 2.6.1 ???
Answer by AlexFoo
Nov 15, 2010 at 07:28 AM
Now, how do I get the 2nd instance of Unity3D to sync with a second instance of MonoDevelop? Everytime I press Asset>Sync monodevelop on the 1st or 2nd instance of Unity3D, it will always sync with the first instance of monodevelop, although I had 2 opened monodevelop(for unity) instance.
Try opening both solutions in a single instance of MonoDevelop. With one solution open in MonoDevelop, use File->Open... and select the .sln of the second project. Be sure to uncheck "Close current workspace" before clicking the "Open" button.
Answer by TowerOfBricks
Nov 29, 2009 at 09:42 AM
I don't think you can have multiple Unity projects open at the same time, add it to the wish list on the forums if you want to have the functionality.
Please see my answer below.
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