BRL-CAD external dependencies

This repository holds local copies of dependencies used by the BRL-CAD computer aided design system.

Quick start

• Clone this repository

git clone https://github.com/BRL-CAD/brlcad_externals

• Make a build directory

mkdir brlcad_externals_build && cd brlcad_externals_build

• Configure with CMake. Individual components can be enabled or disabled, but the ENABLE_ALL flag is used to automatically turn on all the projects targeted for BRL-CAD bundling.

cmake ../brlcad_externals -DENABLE_ALL=ON

• Run the build process.

cmake --build . --config Release --parallel 8

Using the Build Outputs with BRL-CAD

At the moment this repository and BRL-CAD's support of it are still experimental. To test it, the steps are as follows:

• Clone the BRL-CAD repository

git clone https://github.com/BRL-CAD/brlcad

• Remove the internal 3rd party directories (be sure NOT to accidentally commit this change to the repository...)

cd brlcad && rm -rf misc/tools/ext src/other

• Make a build directory

cd .. && mkdir brlcad_exttest_build && cd brlcad_exttest_build

• Configure with CMake. If no custom CMAKE_INSTALL_PREFIX was supplied to the brlcad_externals build, BRL-CAD will know to look for the folder it needs in the user's home directory. If a custom location was used, specify the path holding the brlcad_ext output directory using -DBRLCAD_EXT_DIR=<your_root> (brlcad_ext should in turn contain the extinstall and extnoinstall folders.) If you also wish to test with Qt, you must currently enable that support in BRL-CAD as well. (Note that the BRL-CAD configure process is responsible for staging the BRLCAD_EXT_DIR contents into the build directory, so it can take some time to complete...)

cmake ../brlcad -DBRLCAD_ENABLE_QT=ON

• Run the build process.

cmake --build . --config Release --parallel 8
cmake --build . --target package --parallel 8

If all goes well, the final result should be a relocatable BRL-CAD archive including both the main BRL-CAD outputs and the products of this external dependencies repository.

About This Repository

There are, broadly speaking, three categories of project repositories included here:

• Build tools used for compiling this repository and/or BRL-CAD proper, that are not distributed with it.

• Bundled versions of 3rd party dependencies intended to be distributed with BRL-CAD, but that are not modded to exhibit behavior different that that which would be found in a system installed version.

• Third party libraries that have modifications from upstream that are a) not of interest to the upstream and b) required for correct functioning in BRL-CAD. Sometimes there is also no active upstream to provide support.

Although it is possible to install the products of these builds to system locations and have BRL-CAD detect them there, the intended approach is for BRL-CAD to bundle these dependences and provide them directly as part of its own installers. This allows (for example) Windows installations of BRL-CAD to be far more self contained - users on such platforms generally expect to be able to download and use a software package immediately, regardless of what is or is not already present on the operating system.

The presence of the first and third categories basically implies that BRL-CAD's main build will, at some level, require elements of this repository to build even if a full set of system dependencies is present - there will be cases such as openNURBS where we have deliberately modified the behavior of the library. The advantages of managing those dependencies in this fashion none the less is two fold: 1) for those dependencies with active upstreams, it simplifies merging in new versions to our build and 2) once compiled, this repository's build outputs can be reused for many BRL-CAD compile/debug cycles without having to repeat the full src/other build process.

The main BRL-CAD repository manages the bundling process - this repository's responsibility is to prepare suitable inputs and manage the 3rd party building processes across all targeted platforms.

In broad, the structure of the source tree is two tiered - the top level directories each denote a specific dependency project (Tcl, Qt, GDAL, etc.). Within that directory are found:

• The upstream source code (usually this should be a vanilla copy of the upstream)
• Our managing CMakeLists.txt file defining the logic for building that project
• Any patch files or other supporting resources not part of the upstream build.

Sometimes third party libraries will depend on other third party libraries (for example, libpng's use of zlib) - when a bundled component that is a dependency of other bundled projects is enabled, the expectation is that the other bundled components will use our copy rather than system copies of those libraries.

BRL-CAD Compilation Tools

Although most of the components here are intended for bundling with BRL-CAD, there are a few exceptions to that rule. A few of the projects (AStyle, patch, LIEF, etc.) target a different installation folder and are used only for BRL-CAD compilation (and/or support for building this externals repository.)

There are also header-only "libraries" such as Eigen that are needed only for BRL-CAD compilation, and do not need to be distributed with our packages.

To figure out which projects are in these categories, check for a CMAKE_NOBUNDLE_INSTALL_PREFIX target being used by their top level CMakeLists.txt file managing the ExternalProject_Add build definition.