Source tree

lysa_tutorial_01/
├── CMakeLists.txt
├── .env.cmake (user-supplied)
├── shaders/ (populated at build time)
└── src/
    ├── Main.cpp
    ├── MainWindow.ixx
    ├── Camera.ixx / .cpp
    ├── SceneInstance.ixx / .cpp
    ├── SceneTree.ixx / .cpp
    └── RotatingAssetScene.ixx / .cpp

Engine integration

The Lysa engine is integrated as a CMake subdirectory rather than a pre-built library. add_subdirectory compiles the engine in-tree and makes the lysa_engine and lysa_engine_shaders targets available to the project:

set(LYSA_ENGINE_TARGET "lysa_engine")
set(LYSA_ENGINE_TARGET_SHADERS "${LYSA_ENGINE_TARGET}_shaders")
set(LYSA_ENGINE_SHADERS_BUILD_DIR ${LYSA_ENGINE_PROJECT_DIR}/shaders)
add_subdirectory(${LYSA_ENGINE_PROJECT_DIR} external_lib_build/${LYSA_ENGINE_TARGET})

Several feature flags can be set before the add_subdirectory call to control which engine subsystems are compiled:

Variable	Default	Effect
`LUA_BINDING`	`OFF`	Lua scripting bindings
`FORWARD_RENDERER`	`ON`	Forward rendering pipeline
`DEFERRED_RENDERER`	`ON`	Deferred rendering pipeline
`PHYSIC_ENGINE_JOLT`	`OFF`	Jolt physics backend
`PHYSIC_ENGINE_PHYSX`	`OFF`	PhysX physics backend
`DIRECTX_BACKEND`	`ON` (Windows only)	DirectX 12 backend

Shader copy

Engine shaders are compiled into ${LYSA_ENGINE_PROJECT_DIR}/shaders as part of the lysa_engine_shaders target. A custom target shaders_copy copies that directory into the project's own shaders/ folder, which is where the app://shaders virtual path resolves at runtime:

add_custom_target(shaders_copy
    COMMAND ${CMAKE_COMMAND} -E copy_directory
        ${LYSA_ENGINE_SHADERS_BUILD_DIR}
        ${SHADERS_BUILD_DIR}
    COMMENT "Copying shaders"
    VERBATIM
)
add_dependencies(shaders_copy ${LYSA_ENGINE_TARGET} ${LYSA_ENGINE_TARGET_SHADERS})

Application target

The build_target function encapsulates the boilerplate for creating an executable that uses C++ modules: it calls add_executable for plain .cpp sources, registers .ixx module interface files via FILE_SET CXX_MODULES, applies the engine's compile options, and links against lysa_engine:

function(build_target TARGET_NAME SRCS MODULES)
    add_executable(${TARGET_NAME} ${SRCS})
    target_sources(${TARGET_NAME}
        PUBLIC FILE_SET CXX_MODULES FILES ${MODULES})
    lysa_compile_options(${TARGET_NAME})
    target_link_libraries(${TARGET_NAME} ${LYSA_ENGINE_TARGET})
    add_dependencies(${TARGET_NAME} shaders_copy)
endfunction()

The sample application is built with:

set(MY_TARGET_SRC
    ${SRC_DIR}/Main.cpp
    ${SRC_DIR}/Camera.cpp
    ${SRC_DIR}/SceneInstance.cpp
    ${SRC_DIR}/SceneTree.cpp
    ${SRC_DIR}/RotatingAssetScene.cpp
)
set(MY_TARGET_MODULES
    ${SRC_DIR}/MainWindow.ixx
    ${SRC_DIR}/Camera.ixx
    ${SRC_DIR}/SceneInstance.ixx
    ${SRC_DIR}/SceneTree.ixx
    ${SRC_DIR}/RotatingAssetScene.ixx
)
build_target(myapp "${MY_TARGET_SRC}" "${MY_TARGET_MODULES}")

Note that .ixx module interface files and their .cpp implementation files are listed separately: interfaces go into MY_TARGET_MODULES (the CXX_MODULES file set), while plain translation units go into MY_TARGET_SRC.

Next : Engine context