STEP read and write without application framework

[petrasvestartas]

Is it possible to make an example of the video of OCCT: https://www.youtube.com/watch?v=dq2-evewPeA
Without using application framework?

Meaning I create a breps and write them to a step file.

Why the application framework is used here?

[dpasukhi]

Hello. No, that functionality is not possible.
That feature will return after integration new "DE framework, which is under development".
XCAF is required to any DE formats at the moment.

[dpasukhi]

That error can be resolved after installing the open GL lib.
After installing, it will work without visualisation part. But that lib is required to with with OCCT.
No possibility to skip that step for DE part. If you are interested to improve something, we are open to contributions.

[petrasvestartas]

When simply writing and reading files: https://dev.opencascade.org/doc/overview/html/occt_user_guides__step.html#occt_step_3_7

Do I still need the whole application workflow?

[dpasukhi]

Partially, not whole, but all required toolkits which enables automatically.

[petrasvestartas]

Then it means i need to add 3rd parties to make this work, I will roll my sleeves and will try to make them work :)

Thank you

[dpasukhi]

No needs to 3rd party. OpenGl is used indirectly, but need to be installed during build process

[petrasvestartas]

Hi again,

I am struggling with this tutorial 15, where I am trying to make this example work from a cmake project.

What I am essentially missing here?

cmake_minimum_required(VERSION 3.15)
project(compas_occt LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

include(ExternalProject)
find_package(Python 3.8 REQUIRED COMPONENTS Interpreter Development.Module Development.SABIModule)
find_package(nanobind CONFIG REQUIRED)
find_package(Threads REQUIRED)

# ------------------------------------------------------------------------------
# Eigen (header-only library)
# ------------------------------------------------------------------------------
set(EIGEN_DIR "${CMAKE_CURRENT_SOURCE_DIR}/external/eigen")
file(MAKE_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/external") # Create directories if they don't exist
add_custom_target(eigen_ext) # This two-target approach solves the issue of first downloading then building our libraries
message(STATUS "---------------------- Eigen: ${EIGEN_DIR}")

if(NOT EXISTS "${EIGEN_DIR}/Eigen")
    ExternalProject_Add(
        eigen_download
        URL https://gitlab.com/libeigen/eigen/-/archive/3.4.0/eigen-3.4.0.zip
        PREFIX ${CMAKE_BINARY_DIR}/deps/eigen
        SOURCE_DIR ${EIGEN_DIR}
        CONFIGURE_COMMAND ""
        BUILD_COMMAND ""
        INSTALL_COMMAND ""
        TEST_COMMAND ""
    )
    add_dependencies(eigen_ext eigen_download)
endif()

# ------------------------------------------------------------------------------
# OCCT (static libraries)
# ------------------------------------------------------------------------------
set(CMAKE_DEPS_DIR ${CMAKE_BINARY_DIR}/deps)
set(OCCT_PREFIX ${CMAKE_DEPS_DIR}/occt) # Create needed directories
file(MAKE_DIRECTORY ${CMAKE_DEPS_DIR})
set(OCCT_SRC_DIR ${OCCT_PREFIX}/src/occt)
set(OCCT_BUILD_DIR ${OCCT_PREFIX}/src/occt-build)
set(OCCT_INSTALL_DIR ${OCCT_PREFIX}/install) # Use the same custom install path as specified in ExternalProject_Add
set(OCCT_INCLUDE_DIR "${OCCT_INSTALL_DIR}/my_include" CACHE PATH "Path to OCCT headers" FORCE) # Use the same custom include path as specified in ExternalProject_Add
set(OCCT_LIB_DIR "${OCCT_INSTALL_DIR}/my_static_libs" CACHE PATH "Path to OCCT libraries" FORCE)

message(STATUS "---------------------- OCCT_INCLUDE_DIR: ${OCCT_INCLUDE_DIR}")
message(STATUS "---------------------- OCCT_LIB_DIR: ${OCCT_LIB_DIR}")

if(WIN32)
    set(LIB_PREFIX "")
    set(LIB_EXT ".lib")
else()
    set(LIB_PREFIX "lib")
    set(LIB_EXT ".a")
endif()

# OCCT has many static libraries. Generate the library targets list using OCCT_LIB_DIR.
set(OCCT_LIB_TARGETS "")
set(OCCT_MODULES TKBool TKFillet TKOffset TKFeat TKPrim TKBO TKMesh TKHLR TKShHealing TKTopAlgo TKGeomAlgo TKBRep TKGeomBase TKG3d TKG2d TKMath TKernel)
# Add STEP support libraries from DataExchange module
list(APPEND OCCT_MODULES TKDE TKXSBase TKDESTEP)
# Add Application Framework and XCAF libraries for STEP support
list(APPEND OCCT_MODULES TKXCAF TKLCAF TKCAF TKBinXCAF TKBin TKCDF TKXmlXCAF TKXml TKStd)
# Add Storage module for Storage_HeaderData
list(APPEND OCCT_MODULES TKStorage)
foreach(MODULE ${OCCT_MODULES})
    list(APPEND OCCT_LIB_TARGETS "${OCCT_LIB_DIR}/${LIB_PREFIX}${MODULE}${LIB_EXT}")
endforeach()

add_custom_target(occt_ext) # This two-target approach solves the issue of first downloading then building our libraries

if(NOT EXISTS "${OCCT_INSTALL_DIR}/my_include" OR NOT EXISTS "${OCCT_INSTALL_DIR}/my_static_libs")
    ExternalProject_Add(
        occt_download
        URL https://github.com/Open-Cascade-SAS/OCCT/archive/refs/tags/V7_9_0.zip
        PREFIX ${OCCT_PREFIX}
        SOURCE_DIR ${OCCT_SRC_DIR}
        BINARY_DIR ${OCCT_BUILD_DIR}
        CMAKE_ARGS
            -DCMAKE_INSTALL_PREFIX=${OCCT_INSTALL_DIR}
            # Use OCCT-specific install directory variables without quotes
            -DINSTALL_DIR_LIB=my_static_libs 
            -DINSTALL_DIR_INCLUDE=my_include 
            -DINSTALL_DIR_LAYOUT=Unix
            # Other build options
            -DCMAKE_BUILD_TYPE=Release
            -DBUILD_LIBRARY_TYPE=Static
            -DBUILD_MODULE_Draw=OFF
            -DBUILD_MODULE_ApplicationFramework=ON
            -DBUILD_MODULE_DataExchange=ON
            -DBUILD_MODULE_Visualization=OFF
            -DBUILD_MODULE_STEP=ON
            -DBUILD_SAMPLES_QT=OFF
            -DBUILD_USE_PCH=ON
            # Remove 3rd parties
            -DUSE_FFMPEG=OFF
            -DUSE_FREETYPE=OFF
        # Must build AND install the libraries to the custom location
        BUILD_COMMAND ${CMAKE_COMMAND} --build . --config Release # -j4
        INSTALL_COMMAND ${CMAKE_COMMAND} --install . --config Release
        BUILD_BYPRODUCTS ${OCCT_LIB_TARGETS}
    )
    
    add_dependencies(occt_ext occt_download)
endif()

# ------------------------------------------------------------------------------
# Build nanobind Python modules
# ------------------------------------------------------------------------------

function(add_nanobind_module module_name source_file)
    nanobind_add_module(${module_name} ${source_file})                                          # Creates the Python extension module with nanobind
    target_include_directories(${module_name} SYSTEM PRIVATE ${EIGEN_DIR} ${OCCT_INCLUDE_DIR})  # Add include paths for headers (SYSTEM suppresses warnings)
    add_dependencies(${module_name} eigen_ext occt_ext)                                         # Ensures Eigen and OCCT are built before this module
    target_link_libraries(${module_name} PRIVATE ${OCCT_LIB_TARGETS})                           # Links against all the OCCT static libraries
    install(TARGETS ${module_name} LIBRARY DESTINATION compas_occt)                             # Installs the compiled module to the compas_occt package
endfunction()

add_nanobind_module(_primitives src/primitives.cpp)
add_nanobind_module(_curves src/curves.cpp)
add_nanobind_module(_nurbssurface src/nurbssurface.cpp)
add_nanobind_module(_step src/step.cpp)

[dpasukhi]

Please, use CMake debugger to validate the process. I don't know and don't see logs from here

[petrasvestartas]

I am using but it is not clear what is the total set of build libraries needed. Do you have a complete list for application and step functionality?

# OCCT has many static libraries. Generate the library targets list using OCCT_LIB_DIR.
set(OCCT_LIB_TARGETS "")
set(OCCT_MODULES TKBool TKFillet TKOffset TKFeat TKPrim TKBO TKMesh TKHLR TKShHealing TKTopAlgo TKGeomAlgo TKBRep TKGeomBase TKG3d TKG2d TKMath TKernel)
# Add STEP support libraries from DataExchange module
list(APPEND OCCT_MODULES TKDE TKXSBase TKDESTEP)
# Add Application Framework and XCAF libraries for STEP support
list(APPEND OCCT_MODULES TKXCAF TKLCAF TKCAF TKBinXCAF TKBin TKCDF TKXmlXCAF TKXml TKStd)
# Add Storage module for Storage_HeaderData
list(APPEND OCCT_MODULES TKStorage)

Originally I only had those, but now I do not know which ones are needed:
set(OCCT_MODULES TKBool TKFillet TKOffset TKFeat TKPrim TKBO TKMesh TKHLR TKShHealing TKTopAlgo TKGeomAlgo TKBRep TKGeomBase TKG3d TKG2d TKMath TKernel)

Most often I have error:
ImportError: /home/pv/anaconda3/envs/occ/lib/python3.12/site-packages/compas_occt/_step.cpython-312-x86_64-linux-gnu.so: undefined symbol: _ZTI17BRepLib_MakeShape

[dpasukhi]

When you link using CMake, the related dependencies are linked (in case of find_packge). In your case you are using custom approache, which can't guarantee simple integration, I do not have a list for your use case.

[petrasvestartas]

What would be the best way to build occt so that all the libraries are included?

[dpasukhi]

Use it out of CMake script. For example make build on step before in bash or use vcpkg and then use find_package.
Using OCCT inside CMake is not supported by default.