Updating Engine After Building From Source

Howdy there!

A few weeks ago I attempted to build from source and it was successful which was built on 4.9.0. Earlier this week 4.9.1 was released and that sparked a question for me that I can’t seem to find the answer to. Is there a documentation link hidden somewhere that explains how you update the engine from whatever version you started with (in my case 4.9.0) to a newer version (for me I want to go to 4.9.1)? I’m not sure if its as simple as downloading the new source files then rebuild and regenerate the project files or if there is some different method of doing so.

Did you clone the github repository? If so, the quick way would be performing a “remote update” to sync with the changes from Epic, then re-generate the project files and recompile.

Personally, I would check out to a different folder, compile it there then open a copy of the project in the new version, for maximum safety.

This depends on whether or not you have made any modifications to the engine source code.

If No:
Just go to the UE4 github page and download the zip file for the latest engine source code. Once it finishes downloading, click the “setup.bat” file, let it download 3gb of dependencies, then click “GenerateProjectFiles.bat” and let that build your sln and project files. Once that’s done, just open the SLN file, select the build configuration you want, then select “Debug -> Start new instance”. The engine will compile and after about 30-60 minutes, it will launch UE 4.9.1

If Yes:
You’ll want to make sure that you migrate any engine changes you made to the latest version of the engine. Download the source from the github zip as usual, download dependencies, etc.
Before you build the engine, you’ll want to copy any of your source code mods over from 4.9.0 to 4.9.1. The easiest way to do this is to get a file comparison tool to parse the whole engine source directory (I use Beyond Compare). Then go through each diff and copy the modded diffs from 4.9.0 source to 4.9.1. Then run “Debug -> start new instance” and proceed as usual.

engine source directory? as in …/engine or …/engine/source ?