CMake Settings Reference

Open 3D Engine uses custom CMake configuration values in order to detect settings like valid deployment platforms, active projects, and the locations of downloaded packages. This document is a reference for the user-available CMake settings used by O3DE. Settings specific to a Gem are covered in Gem reference. For general CMake options, see the cmake-variables documentation .

Keep in mind that every time you change a configuration value, you need to regenerate the project files so that the changes are picked up and apply to your next build.

CMake options like CMAKE_CXX_STANDARD are set during configuration automatically by O3DE. Changing these values can break your ability to compile O3DE code, so edit them with care.

Cache values

Required settings

These options are the user-supplied settings that are required to configure O3DE builds. Make sure that these values are set before running your first configure, and only change them later if necessary.

  • LY_3RDPARTY_PATH - The filesystem path to your package directory. Changing this value requires reconfiguration, and will prompt another install of packages. See packages for more information.

    Type: PATH

Build configuration

  • LY_UNITY_BUILD - Controls the generation of unity build files. Unity builds speed up build times by taking multiple .cpp files and merging them together into a single compilation unit.

    Make sure that this option is turned ON if you experience slow build times for your projects, the O3DE engine, or O3DE tools. The impact is most dramatic for systems with lots of available RAM but fewer available cores or low disk throughput.

    Type: BOOL
    Default: ON

  • LY_MONOLITHIC_GAME - Controls project library linking. When this value is set to ON, it provides a compiler hint to use static libraries where possible. Some libraries, such as PhysX, are only available as shared libraries and can’t be statically linked. Some platforms may disable static linking entirely.

    Type: BOOL
    Default: OFF

  • LY_LINKER - Sets the linker program to be used during the build process. If this value is not set, a default linker is chosen based upon the available linker programs installed on the host platform. Currently only supported for the Linux x86 Clang configuration.

    Type: STRING Default: (Empty string)

Asset configuration

These options control the types of assets that are built, and where projects load assets from at runtime.

  • LY_ASSET_DEPLOY_TYPE - The default type of assets to be built by Asset Processor. Valid platforms are:

    • pc - Windows PC
    • linux - Linux
    • mac - MacOS
    • ios - iOS and iPad OS
    • android - Android

    Type: STRING
    Default: The asset type for the current host platform.

  • LY_ASSET_DEPLOY_MODE - Controls how projects load assets at runtime. Allowed values are:

    • LOOSE - Load assets on demand from the asset cache, after sources are processed by the Asset Processor. This setting is appropriate for development.
    • PAK - Only load assets from .pak asset bundles created by the Asset Bundler. Which directories to load asset bundles from is controlled with the LY_OVERRIDE_PAK_FOLDER_ROOT setting.
    • VFS - Load data from the virtual filesystem server (VFS).

    Type: STRING
    Default: LOOSE

    Defines the default file search mode to locate non-Pak files within the Archive System

    • 0 = Search file system first, before searching within mounted .pak files.
    • 1 = Search mounted .pak files first, before searching file system.
    • 2 = Search only mounted .pak files.

    Type: STRING
    Default: 0 = (debug/profile configurations), 2 = (release configuration)

Package system settings

These settings control how the package download system functions.

  • LY_PACKAGE_DEBUG - Produces verbose information about the package download and installation process when ON. Set this cache value before filing any bug report against the O3DE package system to make sure that all the necessary information is there to resolve the issue.

    Type: BOOL
    Default: OFF

  • LY_PACKAGE_DOWNLOAD_CACHE_LOCATION - The download cache for packages pulled from a remote server. This cache is never emptied if LY_PACKAGE_KEEP_AFTER_DOWNLOADING is ON.

    Type: PATH
    Default: ${LY_3RDPARTY_PATH}/downloaded_packages

  • LY_PACKAGE_KEEP_AFTER_DOWNLOADING - Whether or not to keep downloaded packages in the cache, even after installation.

    Type: BOOL
    Default: ON

  • LY_PACKAGE_SERVER_URLS - The URLs for servers to pull packages from, as a semi-colon (;) separated list. These can be http, https, file, or s3 URLs. These values are prepended to any LY_PACKAGE_SERVER_URLS environment variable.

    Type: STRING
    Default: (Empty string)

  • LY_PACKAGE_UNPACK_LOCATION - The location where downloaded packages are unpacked to, before being relocated to the package folder.

    Type: PATH
    Default: ${LY_3RDPARTY_PATH}/packages

  • LY_PACKAGE_VALIDATE_PACKAGE - Validate packages against checksums in the requesting CMake file, redownloading the package from sources as necessary.

    Type: BOOL Default: OFF

  • LY_PACKAGE_VALIDATE_CONTENTS - Check each file against the hashes contained in the SHA256SUMS of the package. When this value is OFF, the checksums are validated only on the first package download. Turning this setting on allows for checking for local modifications to the package, but will slow down configuration.

    Type: BOOL Default: OFF

  • LY_PACKAGE_DOWNLOAD_RETRY_COUNT - The number of times to attempt retrieval from a package source if an error occurs in the transfer.

    Type: Integer Default: 3

Build/Debugging Tools

  • LY_BUILD_WITH_ADDRESS_SANITIZER - Enables Address Sanitizer (ASan).

    Currently only supported for Windows and “Visual Studio” generators. Documentation can be found here

    Type: BOOL Default: OFF

  • O3DE_BUILD_WITH_DEBUG_SYMBOLS_RELEASE - Generates symbol files (.pdb) in release configurations and turns off optimizations making it easier to troubleshoot issues in release builds.

    Currently only supported for Windows and “Visual Studio” generators.

    Type: BOOL Default: OFF

CMake functions reference

Intellisense support for Visual Studio and Visual Studio Code is available in the O3DE CMake files, located in the cmake directory of O3DE source.