Building OFP on Windows

Building OFP on Windows

This page sets up a Windows machine to build OFP's engine and QtFRED from source with Visual Studio. It's based on SCP's Building on Windows page, updated for current tools. For other systems see Building OFP on Linux and Building OFP on Mac.

If you only want to play or make a mod with OFP, you don't need any of this: see Using OFP with Knossos.NET.

What you need

Tool	Notes
Git	Any recent version.
Visual Studio 2022 or 2026	The free Community edition is all you need. In the installer, pick the Desktop development with C++ workload; Visual Studio takes care of the MFC parts the old FRED2 needs.
CMake	3.21 or newer. Visual Studio 2026 needs CMake 4.2 or newer, since older versions have no generator for it. Install the standalone version to get cmake-gui.
Qt 6 (optional)	Used by QtFRED. Install the MSVC 2022 64-bit kit (6.8.3 is known to work, with Visual Studio 2022 and 2026 alike). If CMake can't find a Qt install, it downloads a prebuilt Qt for you instead.

1. Get the source

Clone the OFP repository with its submodules:

git clone --recursive https://github.com/ofp-fs2open/fs2open.github.com.git OFP

If you already cloned without --recursive, run this inside the clone:

git submodule update --init --recursive

Without the submodules, CMake stops with External submodules could not be found.

2. Configure with CMake

1. Start cmake-gui.
2. Set Where is the source code to your clone, and Where to build the binaries to a build folder inside it. The build folder must be different from the source folder.
3. If you installed Qt, click Add Entry and add QT6_INSTALL_ROOT (type PATH) set to your Qt kit folder, for example C:/Qt/6.8.3/msvc2022_64. Do this before the first Configure. If you add it later, CMake has already cached the prebuilt Qt and the two get mixed up; use File > Delete Cache and start over.
4. Click Configure. Pick the generator for your Visual Studio (Visual Studio 17 2022 or Visual Studio 18 2026), platform x64, and leave the toolset blank. A 32-bit build can't build QtFRED.
5. When it finishes, look for Using system Qt libraries in the output if you set QT6_INSTALL_ROOT.
6. Set these variables, using forward slashes (/) in paths or the build fails:
   • CMAKE_INSTALL_PREFIX: your FreeSpace 2 folder. The INSTALL target copies the built executables here. The default is C:/Program Files/FS2_Open, which needs admin rights, so change it.
   • FSO_FREESPACE_PATH: also your FreeSpace 2 folder. It lets you run and debug the executables straight from Visual Studio.
7. Click Configure again, then Generate, and wait for Generating done.
8. Click Open Project.

CMake 4.3 and newer write FS2_Open.slnx instead of FS2_Open.sln. If an old FS2_Open.sln is left in the build folder from an earlier CMake, delete it (and the build/.vs folder) so you don't open the stale one.

Useful variables

Variable	Default	What it does
FSO_BUILD_QTFRED	ON	Build QtFRED.
FSO_BUILD_FRED2	ON	Build the old MFC FRED2. Turn it off if you don't use it.
FSO_BUILD_WITH_VULKAN	ON	Build the Vulkan renderer.
FSO_BUILD_WITH_OPENGL	ON	Build the OpenGL renderer.
FSO_BUILD_TESTS	OFF	Build the unit tests.
FSO_BUILD_TOOLS	OFF	Build some FSO tools.
FSO_USE_SPEECH / FSO_USE_VOICEREC	ON	Text-to-speech and voice recognition support.
MSVC_SIMD_INSTRUCTIONS		The instruction set the executables are optimized for (for example AVX).
FSO_RUN_ARGUMENTS		Command line arguments passed when you run an executable from Visual Studio, for example -mod MyMod.

File > Delete Cache resets every one of these to its default, including CMAKE_INSTALL_PREFIX and FSO_FREESPACE_PATH, so note any you changed first.

3. Build

Pick a configuration in Visual Studio's toolbar:

• Debug: for running with the debugger attached. Slow.
• FastDebug: optimized, but keeps the debug checks for mod data. This is what modders usually want: it reports table and mission errors that Release skips.
• Release: fully optimized, for playing.

Then in Solution Explorer, open the CMakePredefinedTargets folder, right-click INSTALL and click Build. This builds everything and copies the executables (plus the DLLs and, for QtFRED, the Qt files they need) into CMAKE_INSTALL_PREFIX.

The first build takes a while (around half an hour for Debug); later builds only rebuild what changed. Warnings C4701/C4703 in sexp.cpp and vk_mem_alloc.h and the CMP0219 policy warning are expected.

4. Run and debug from Visual Studio

With FSO_FREESPACE_PATH set, right-click the Freespace2 or qtfred project, click Set as Startup Project, and press F5. Put the mod's command line options (such as -mod MyMod) in FSO_RUN_ARGUMENTS, or in the project's Properties > Debugging > Command Arguments.

Keeping up with OFP

To get the latest OFP changes:

git pull
git submodule update --init --recursive

Visual Studio reruns CMake by itself when CMake files change. If you move to a new Visual Studio version, the old build folder won't build (error MSB8020, toolset not found): delete the cache and configure again with the new generator, as in step 2.