Needing to run two Unity Editor Instances at same time.

Questions & Answers
1

I am trying to port from one project to another, and since this doesn't seem to be a clean process, I am wanting to have two instances of Unity Open at same time -- with one instance pointing at the source project and the other instance pointing at my target instance.

But since Unity.exe always starts up the last project, and this is not allowed, I am not able to run two instances at the same time.

Is there a command line option for starting Unity where I can force it to load a project at a specified absolute path? (I believe this would then allow me to run two instances at once, and do a side-by-side comparison of them as I do the porting.)

3

A more extensive answer can be found here.

4

Although Ehren's answer contains the solution I think you're looking for here, I think the only bit you really need for this purpose is:

Edit > Preferences > Show Project Wizard at Startup (tick on)

Then each time you open Unity you can choose which project to open.

2

I found the answer by using Google Search for "Unity3d Command Line", and found this nice link:

http://unity3d.com/support/documentation/Manual/Command%20Line%20Arguments.html

It says I can do this using the "-projectPath" argument followed by my full project path.

I just tested it and it works.