/**

@page build Building OpenVDB

@section buildContents Contents
- @ref buildIntroduction
- @ref buildCmakeStructure
  - @ref buildDependencies
  - @ref buildMixingDepInstalls
  - @ref buildBloscSupport
  - @ref buildZLibSupport
  - @ref buildVCPKG
- @ref buildComponents
- @ref buildGuide
  - @ref buildBuildTypes
  - @ref buildBuildHouMaya
    - @ref buildBuildHou
    - @ref buildBuildMaya
  - @ref buildBuildStandalone
- @ref buildUsingOpenVDB
- @ref buildTroubleshooting
<!-- - @ref buildContents -->

------------------------------------------------------------------------------

@section buildIntroduction Introduction

[CMake](https://cmake.org/) is a cross-platform family of tools designed to
help build software.
CMake doesn't *actually* build the project but instead generates the files
required for your toolchain, for example makefiles that serve as input to
[GNU Make](https://www.gnu.org/software/make/).
CMake support ensures a high level of
flexibility and pre-compile verification to the build process, making it much
easier to control and customize the installation process for a wider range of
platforms.

CMake also makes it easier to automatically find and handle dependencies.
If you're completely new to CMake, you may find it useful to read over the
brief [introduction to CMake](https://cmake.org/runningcmake/) and the CMake
structure section below. However the [build guide](@ref buildGuide) runs
through the build process step by step.

@section buildCmakeStructure CMake Structure

CMake will configure a set of build files which represent the commands and
dependencies for the OpenVDB components you wish to install. Finding and
handling these dependencies on different platforms comprises the majority
of the complexity involved in writing CMake. In general, software which uses
CMake is expected to provide their own configuration files which dependent
software will locate and use. Not all of OpenVDB's dependencies provide CMake
support and therefore do not deploy with CMake configurations that OpenVDB can
use. OpenVDB provides a set of `FindModules` in the `cmake` folder for finding
these various dependencies e.g. `FindBlosc.cmake`. These are designed such
that they can theoretically be used by any project that needs to locate the
given library and are invoked by the `find_package()` call. For more
information on FindModules and locating packages with CMake, see the following
CMake documentation:

 - [Using Packages with CMake](https://cmake.org/cmake/help/latest/manual/cmake-packages.7.html#using-packages)
 - [Calling find_package()](https://cmake.org/cmake/help/latest/command/find_package.html)

The other type of file provided by OpenVDB are `OpenVDBSetupX.cmake` includes.
These are primarily designed to configure the building of OpenVDB components
against supported DCC's (Houdini/Maya) by locating their installations and
setting various CMake variables for subsequent `find_package()` dependency
calls. They also represent packages which already provide their own CMake
modules, but additionally provide the same input variable interface as OpenVDB's
other `Find` Modules.

@subsection buildDependencies Locating Dependencies

Each CMake FindModule provides a description of the possible inputs which can
be provided to help drive the search for OpenVDB dependencies (as well as the
resulting outputs). They have been homogenized such that these variables
follow a set convention, typically followed by most CMake projects. For a
given FindModule e.g. `FindBlosc.cmake`:

  - FindXxx.cmake provides the module interface where Xxx becomes the library
  name
  - Invoked with the called `find_package( Xxx )`
.
  - @b Inputs - The following variables can be used to help drive the search
  path on first runs of CMake (i.e. these variables are not
  [cached](https://cmake.org/cmake/help/latest/command/set.html#set-cache-entry)).
  They are listed in priority order. Note that the prefix is always capitalized.
   - @b Xxx_ROOT - Preferred installation prefix. The given dependency is
   expected to follow a folder structure `Xxx_ROOT/include` and `Xxx_ROOT/lib`
   exist. Note that unlike the above, this is the case matching name of the
   find package .i.e. Blosc_ROOT, IlmBase_ROOT, TBB_ROOT etc.
   - @b XXX_INCLUDEDIR / @b XXX_LIBRARYDIR - Preferred include and library
   directories
   - @b SYSTEM_LIBRARY_PATHS - A list of paths appended to all include and lib
   searches.
   - @b XXX_USE_STATIC_LIBS - Only search for static libraries for the given
   dependency. If OFF, the shared library is prioritized, falling back
   to the static library. This is OFF by default.
   - @b DISABLE_CMAKE_SEARCH_PATHS - The above variables are custom to the
   OpenVDB project. CMake itself implements its own search system to try and
   find the given libraries and packages. When ON, this variable
   disables CMake's inbuilt search, guaranteeing that only the above user
   provided paths are searched. See [CMakes Search Procedure](https://cmake.org/cmake/help/latest/command/find_package.html#search-procedure)
   for more information. This is OFF by default (and thus CMake's search
   is enabled).
.
  - @b Outputs The following variables are always set if the project is found:
    - @b Xxx_FOUND - True if the headers and library was found and exists
    - @b Xxx_VERSION - The library version
    - @b Xxx_INCLUDE_DIRS - A list of paths to all required include directories
    - @b Xxx_RELEASSE_LIBRARY_DIRS - A list of paths to all required release library directories
    - @b Xxx_DEBUG_LIBRARY_DIRS - A list of paths to all required debug library directories
    - @b Xxx_RELEASE_LIBRARIES - A list of libraries needed to use the release version of Xxx
    - @b Xxx_DEBUG_LIBRARIES - A list of libraries needed to use the debug version of Xxx
  - Each module produces an [imported target](https://cmake.org/cmake/help/latest/command/add_library.html#imported-libraries)
  in the form @b Xxx::xxx, and may generate multiple imported targets if multiple
  components are found.

@subsection buildMixingDepInstalls Mixing Dependency Installations

There may be a situation where you use a package manager to install some
dependencies, use a DCC such as Maya to provide others and manually build and
install others from source. Care must be taken when providing CMake with these
locations to ensure that the correct files are used. Incorrect use of the above
variables can lead to difficult to diagnose build and runtime errors.

As an example, let's assume we have a manual installation of TBB (either through
a Maya installation or a manual installation from source) and we want to use
this with other dependencies installed through a package manager such as
homebrew. As homebrew copies all headers and libraries it installs to a
`<homebrew>/include` `<homebrew>/lib` directory structure, it can be tempting
to set @b Xxx_ROOT variables to points to the `<homebrew>` folder. However you
may already have an existing installation of TBB through your package manager,
potentially installed by as a dependency of a completely unrelated piece of
software. Whilst CMake may report to you the correct include/lib path, this can
end up being hidden at compile time through these types of shared installations.
You should not rely on the dependency order of the CMake build system - instead,
it's important that you try to use the explicit directory paths where possible.
For example homebrew will install each piece of software to
`<homebrew>/Cellar/<dep_name>/<dep_version>`, where the subsequent include and
library directories can be passed to @b XXX_INCLUDEDIR and @b XXX_LIBRARYDIR
respectively.

In summary try to stick to a single installation workflow and, if in doubt,
provide direct include/lib paths to isolated software locations.

@subsection buildBloscSupport Blosc Support

Blosc is an optional dependency of all OpenVDB components. The documented
build steps below treat blosc as a required dependency. There are two reasons
for this:

 - Blosc produces significantly smaller `.vdb` files
 - If Blosc is disabled, you will not be able to read or use any `.vdb` files
   that were created using blosc compression. This includes OpenVDB files from
   Houdini.

See the note in the [known issues list](@ref depKnownIssues) regarding supported
versions of blosc.

@subsection buildZLibSupport ZLIB Support

ZLIB is an optional dependency of all OpenVDB components. The documented build
steps below treat ZLib as a required dependency.

You can disable ZLib using `-D USE_ZLIB=OFF` if Blosc is also disabled using `-D USE_BLOSC=OFF`.

@subsection buildVCPKG Building Dependencies using VCPKG

It is recommended to set the VCPKG_DEFAULT_TRIPLET=x64-windows environment
variable to use 64-bit libraries by default as even on a 64-bit Windows OS,
VCPKG builds and installs 32-bit libraries by default.

@section buildComponents OpenVDB Components

The following table lists all targets (mainly library and binary components)
which can be built through the CMake build system. They can be set when using
CMake from the command line with `-D VAR=ON/OFF` or with a CMake gui:

Component                 | Description                                                            | CMake Variable                                    | Default    |
------------------------- | ---------------------------------------------------------------------- | ------------------------------------------------- | ---------- |
OpenVDB Core Library      | The Core OpenVDB shared/static library                                 | OPENVDB_BUILD_CORE                                | ON         |
OpenVDB Print             | Command line binary for displaying information about OpenVDB files     | OPENVDB_BUILD_BINARIES / OPENVDB_BUILD_VDB_PRINT  | ON / ON    |
OpenVDB LOD               | Command line binary for generating volume mipmaps from an OpenVDB grid | OPENVDB_BUILD_BINARIES / OPENVDB_BUILD_VDB_LOD    | ON / OFF   |
OpenVDB Render            | Command line binary for ray-tracing OpenVDB grids                      | OPENVDB_BUILD_BINARIES / OPENVDB_BUILD_VDB_RENDER | ON / OFF   |
OpenVDB View              | Command line binary for displaying OpenVDB grids in a GL viewport      | OPENVDB_BUILD_BINARIES / OPENVDB_BUILD_VDB_VIEW   | ON / OFF   |
OpenVDB Python            | Python module for OpenVDB C++ Python bindings                          | OPENVDB_BUILD_PYTHON_MODULE                       | OFF        |
OpenVDB UnitTests         | OpenVDB's Unit Test suite                                              | OPENVDB_BUILD_UNITTESTS                           | OFF        |
OpenVDB Houdini Plugin    | The OpenVDB Houdini shared library and OpenVDB Nodes                   | OPENVDB_BUILD_HOUDINI_PLUGIN                      | OFF        |
OpenVDB Maya Plugin       | The Maya OpenVDB Nodes                                                 | OPENVDB_BUILD_MAYA_PLUGIN                         | OFF        |
OpenVDB AX Library        | The OpenVDB AX library                                                 | OPENVDB_BUILD_AX                                  | OFF        |
OpenVDB AX Binary         | Command line binary for running OpenVDB AX code                        | OPENVDB_BUILD_AX_BINARIES                         | OFF        |
OpenVDB AX Grammar        | Allows for re-generation of AX grammar, typically not required         | OPENVDB_BUILD_AX_GRAMMAR                          | OFF        |
OpenVDB AX Unit Tests     | OpenVDB AX's Unit Test suite                                           | OPENVDB_BUILD_AX_UNITTESTS                        | OFF        |
NanoVDB                   | NanoVDB headers                                                        | OPENVDB_BUILD_NANOVDB                             | OFF        |
NanoVDB Tools             | NanoVDB command line tools                                             | NANOVDB_BUILD_TOOLS                               | OFF        |
NanoVDB Examples          | NanoVDB example binaries and benchmarks                                | NANOVDB_BUILD_EXAMPLES / NANOVDB_BUILD_BENCHMARK  | OFF / OFF  |
NanoVDB Unit Tests        | NanoVDB Unit Test suite                                                | NANOVDB_BUILD_UNITTESTS                           | OFF        |
Documentation             | The OpenVDB doxygen documentation                                      | OPENVDB_BUILD_DOCS                                | OFF        |



@section buildGuide Building With CMake

@subsection buildBuildTypes Build Types

The first step is to decide what type of OpenVDB build you're after. This
primarily boils down to three main options:

 - A standalone OpenVDB build (no Houdini/Maya plugins)
 - OpenVDB for [Houdini](https://www.sidefx.com/)
 - OpenVDB for [Maya](https://www.autodesk.co.uk/products/maya/overview)

Each option provides various benefits. Apart from the support for either the
Houdini or Maya OpenVDB plugins, the latter two options can make it easier for
new users to install the range of OpenVDB dependencies without having to worry
about using a package manager or manually installing for source. You'll still
be able to build and use all components of OpenVDB with these methods. However
depending on the DCC (Digital Content Creation) software's version, you may
find that some features of the Core library are restricted to ensure
compatibility. For more information of building OpenVDB against a Houdini or
Maya installation, see [here](@ref buildBuildHouMaya).

Developers may wish to build a standalone version of OpenVDB to take advantage
of newer dependencies and newer library features. See
[here](@ref buildBuildStandalone) for more information.

@b Note: Blosc and ZLib are treated as required dependencies in these install
instructions. See the [blosc support](@ref buildBloscSupport) and
[zlib support](@ref buildZLibSupport) sections for more information.

@subsection buildBuildHouMaya Building Against Houdini/Maya

Building against a DCC reduces the list of dependencies you need to provide.
You should not mix between Houdini and Maya libraries and should not attempt
to build the Maya plugin using Houdini libraries and vice-versa. Additionally,
it's a good idea to read the above section on
[mixing dependency installations](@ref buildMixingDepInstalls).

DCC      | Supported Version | OpenVDB ABI |
-------- | ----------------- | ----------- |
Houdini  | 19.0              | 8           |
Houdini  | 19.5              | 9           |
Maya     | 2018              | Any         |
Maya     | 2019              | Any         |

@subsection buildBuildHou Building Against Houdini

Houdini ships with a number of libraries that OpenVDB requires. When downloading
Houdini, take note of the file version information. The version you install will
determine the compiler version you should try and use to build OpenVDB. For
example, for @b Linux Houdini 17.5, with a file name of
`houdini-17.5.219-linux_x86_64_gcc6.3.tar.gz`, GCC 6.3 should be used. You
will need to install some of the following dependencies depending on which
OpenVDB components you wish to build.

Package        | Description                                                     | OpenVDB Components |
-------------- | --------------------------------------------------------------- | ------------------ |
CMake          | Cross-platform family of tools designed to help build software  | All                |
C++17 Compiler | Matching Houdini compiler and version                           | All                |
Boost          | Components: iostreams, python, thread                           | All                |
GoogleTest     | A unit testing framework module for C++                         | Unit Tests         |
CppUnit        | A unit testing framework module for C++                         | Unit Tests (AX)    |
GLFW           | Simple API for OpenGL development                               | OpenVDB View       |
Doxygen        | Documentation generation from C++                               | Documentation      |
Log4cplus      | An optional dependency for improved OpenVDB Logging             | Optional (All)     |
NumPy          | Scientific computing with Python                                | Optional (Python)  |
LLVM           | Target-independent code generation                              | OpenVDB AX         |

At a minimum, boost, a matching C++17 compiler and CMake will be required. See
the full [dependency list](@ref dependencies) for help with downloading and
installing the above software. Note that as Blosc and ZLib are provided as part
of the Houdini installation `USE_BLOSC` and `USE_ZLIB` should be left `ON`.

With the necessary dependencies installed, create and enter a directory for
cmake to write to. It's generally useful to create this in the location you've
extracted the OpenVDB repository. It will house CMake's generated build files.

@code{.sh}
mkdir build
cd build
@endcode

Now you can call CMake by providing the absolute or relative path to the root
of the OpenVDB source tree along with the following options:

Required:

  - @b Houdini_ROOT =`/path/to/houdini/install` # Path to Houdini Install
  - @b USE_HOUDINI =`ON` # Force all components to build against Houdini
  - @b OPENVDB_BUILD_HOUDINI_PLUGIN =`ON` # Required for building the Houdini Plugin.

Optional:

  - @b [CMAKE_INSTALL_PREFIX](https://cmake.org/cmake/help/latest/variable/CMAKE_INSTALL_PREFIX.html)
  =`/path/to/install/dir` # The location you wish to install OpenVDB to. See
 the link for default values.
  - @b OPENVDB_HOUDINI_INSTALL_PREFIX =`/path/to/install/dir` # The location to
 install the Houdini plugin to. Defaults to directories defined by Houdini:
    - Linux: `$ENV{HOME}/houdiniX.X`
    - Mac: `$ENV{HOME}/Library/Preferences/houdini/X.X`
    - Windows: `$ENV{HOMEDRIVE}$ENV{HOMEPATH}\Documents\houdiniX.X`
  - @b USE_DEFAULT_HOUDINI_INSTALL =`ON` # Use the above default locations if
  @b OPENVDB_HOUDINI_INSTALL_PREFIX is not specified. If `OFF`, uses the value
  of @b CMAKE_INSTALL_PREFIX.
  - @b BOOST_ROOT =`/path/to/boost/install` # Path to boost. May not be required,
 CMake may find it automatically

For example on MacOS and where the build folder has been created inside the
OpenVDB source root:

@code
cmake -D BOOST_ROOT=/path/to/boost/install \
      -D Houdini_ROOT=/Applications/Houdini/Houdini17.0.506/ \
      -D USE_HOUDINI=ON \
      ../
@endcode

After the CMake build files have been successfully generated, run the build
tool within the build directory to compile the project. On UNIX, you can
typically incoke `make` directly:
@code
make -j4
@endcode

Where the value of the `j` argument is the number of CPU threads to use for a
multi-threaded build. On Windows, you can leverage CMake's build tool to invoke
the selected builder (usually msbuild):
@code
cmake --build .
@endcode

Finally, once a successful build has completed, you can install all files.
@code
cmake --build . --target install   # or simply `make install`
@endcode

See the [troubleshooting](@ref buildTroubleshooting) section for help with
CMake and Make errors.


@subsection buildBuildMaya Building Against Maya

Supported versions of maya only ship with TBB.

Package        | Description                                                       | OpenVDB Components               |
-------------- | ---------------------------------------------------------------   | -------------------------------- |
CMake          | Cross-platform family of tools designed to help build software    | All                              |
C++17 Compiler | Matching Houdini compiler and version                             | All                              |
Boost          | Components: iostreams, python, thread                             | All                              |
ZLIB           | Compression library for disk serialization compression            | All                              |
Blosc          | Recommended dependency for improved disk compression              | All*                             |
GoogleTest     | A unit testing framework module for C++                           | Unit Tests                       |
CppUnit        | A unit testing framework module for C++                           | Unit Tests (AX)                  |
GLFW           | Simple API for OpenGL development                                 | OpenVDB View                     |
Doxygen        | Documentation generation from C++                                 | Documentation                    |
OpenEXR        | EXR serialization support                                         | OpenVDB Render                   |
IlmBase        | Used half precision floating points and EXR serialization support | Optional (All)                   |
Log4cplus      | An optional dependency for improved OpenVDB Logging               | Optional (All)                   |
NumPy          | Scientific computing with Python                                  | Optional (Python)                |
LLVM           | Target-independent code generation                                | OpenVDB AX                       |


* See [blosc support](@ref buildBloscSupport)

At a minimum, boost, a matching C++17 compiler, ZLIB, blosc and CMake will be
required. See the full [dependency list](@ref dependencies) for help with
downloading and installing the above software.

With the necessary dependencies installed, create and enter a directory for
cmake to write to. It's generally useful to create this in the location you've
extracted the OpenVDB repository. It will house CMake's generated build files.

@code{.sh}
mkdir build
cd build
@endcode

Now you can call CMake by providing the absolute or relative path to the root
of the OpenVDB source tree along with the following options:

Required:

  - @b Maya_ROOT =`/path/to/maya/install` # Path to Maya Install
  - @b USE_MAYA =`ON` # Force all components to build against Maya

Optional:

  - @b [CMAKE_INSTALL_PREFIX](https://cmake.org/cmake/help/latest/variable/CMAKE_INSTALL_PREFIX.html)
  =`/path/to/install/dir` # The location you wish to install OpenVDB to. See
 the link for default values.
  - @b OPENVDB_MAYA_INSTALL_PREFIX =`/path/to/install/dir` # The location to
 install the Maya plugin to. Defaults to the value of `${CMAKE_INSTALL_PREFIX}/maya${Maya_VERSION}`
  - @b BOOST_ROOT =`/path/to/boost/install` # Path to boost. May not be required,
 CMake may find it automatically
  - @b IlmBase_ROOT =`/path/to/ilmbase/install` # Path to ilmbase.

For example on MacOS and where the build folder has been created inside the
OpenVDB source root:

@code
cmake -D BOOST_ROOT=/path/to/boost/install \
      -D IlmBase_ROOT=/path/to/ilmbase/install \
      -D Maya_ROOT=/Applications/Autodesk/maya2019/ \
      -D USE_MAYA=ON \
      ../
@endcode

As the Maya plugin is disabled by default, you may also want to add
`-D OPENVDB_BUILD_MAYA_PLUGIN=ON` to the command. The
[components](@ref buildComponents) section shows which targets are enabled by
default.

After the CMake build files have been successfully generated, run the build
tool within the build directory to compile the project. On UNIX, you can
typically incoke `make` directly:
@code
make -j4
@endcode

Where the value of the `j` argument is the number of CPU threads to use for a
multi-threaded build. On Windows, you can leverage CMake's build tool to invoke
the selected builder (usually msbuild):
@code
cmake --build .
@endcode

Finally, once a successful build has completed, you can install all files.
@code
cmake --build . --target install   # or simply `make install`
@endcode

@b Note: The Maya OpenVDB Visualize Node is @b only compatible with Legacy
OpenGL support. You can enable this in Maya by navigating to
`Windows->Settings/Preferences->Preferences->Display` and changing
`Rendering Engine` to OpenGL - Legacy.

See the [troubleshooting](@ref buildTroubleshooting) section for help with
CMake and Make errors.


@subsection buildBuildStandalone Building Standalone

It's recommended you first visit the [dependency list page](@ref dependencies)
before attempting to run CMake on a standalone build. With the necessary
dependencies installed, create and enter a directory for cmake to write to.
It's generally useful to create this in the location you've extracted the
OpenVDB repository. It will house CMake's generated build files.

@code{.sh}
mkdir build
cd build
@endcode

Now you can call CMake by providing the absolute or relative path to the root
of the OpenVDB source tree. Below are some common options you may want to
provide:

- @b [CMAKE_INSTALL_PREFIX](https://cmake.org/cmake/help/latest/variable/CMAKE_INSTALL_PREFIX.html)
=`/path/to/install/dir` # The location you wish to install OpenVDB to. See
the link for default values.
- @b Xxx_ROOT =`/path/to/Xxx/` # Give CMake a path to where a package has been
installed or simply to where your prefered package is installed if it cannot
locate it.

For example, a typical first attempt at generating the build files may look as
follows:

@code{.sh}
cmake -D CMAKE_INSTALL_PREFIX=$HOME/openvdb ../
@endcode

See the [components](@ref buildComponents) section to find which targets are
available, their corresponding CMake flags and their default values.

After the CMake build files have been successfully generated, run the build
tool within the build directory to compile the project. On UNIX, you can
typically incoke `make` directly:
@code
make -j4
@endcode

Where the value of the `j` argument is the number of CPU threads to use for a
multi-threaded build. On Windows, you can leverage CMake's build tool to invoke
the selected builder (usually msbuild):
@code
cmake --build .
@endcode

Finally, once a successful build has completed, you can install all files.
@code
cmake --build . --target install   # or simply `make install`
@endcode

See the [troubleshooting](@ref buildTroubleshooting) section for help with
CMake and Make errors.

@section buildUsingOpenVDB Building With OpenVDB

This section is for users wishing to use a build of OpenVDB in their own
applications with CMake.

The following assumes that OpenVDB was installed with `OPENVDB_BUILD_CORE=ON`
and `OPENVDB_INSTALL_CMAKE_MODULES=ON`. Don't worry if you didn't specify
these options directly, they both default to `ON`. This ensures that OpenVDB
has installed the required CMake modules that your application will need to
use.

@b Note: Typically, projects provide a @b Config-file rather than a
@b Find-module for downstream use. OpenVDB currently provides a @b Find-module.
This may change in the future. Further information
[here](https://cmake.org/cmake/help/latest/manual/cmake-packages.7.html#using-packages).

You can add the below CMake snippet to your main `CMakeLists.txt` to bring in
OpenVDB as a dependency:

@code{.cmake}
cmake_minimum_required(VERSION 3.18)
list(APPEND CMAKE_MODULE_PATH "/location/of/openvdb/install/lib/cmake/OpenVDB")
find_package(OpenVDB REQUIRED)
target_link_libraries(myapp OpenVDB::openvdb)
@endcode

`myapp` in the above is a CMake target, usually created with `add_library()`
or `add_executable()`. You can optionally provide `CMAKE_MODULE_PATH` as a
`-D` argument to the cmake command line instead of specifying it in your
`CMakeLists.txt`.

Note that the `FindOpenVDB.cmake` module relies on the other `FindModules`
provided in the OpenVDB installation to find it's own dependencies. This may
require you to provide additional dependency locations for OpenVDB's
dependencies. See [Locating Dependencies](@ref buildDependencies) or the below
troubleshooting for more information.

------------------------------------------------------------------------------

@section buildTroubleshooting Troubleshooting

If after reading this guide you're unable to find your specific issue below,
please get in touch or [file an issue](https://github.com/AcademySoftwareFoundation/openvdb/issues)
with the OpenVDB TSC.

@b Note: If running into issues when changing CMake settings/dependency paths,
try clearing the designated CMake build directory and running your `cmake`
command again.

@subsection troubleshoot1 CMake Error ... Could NOT find XXX (missing: ... )

It's fairly typical that CMake may fail to find some dependencies on first
runs, especially if you've manually compiled from source your own
dependencies. Analyzing any dependency errors will help with running further
invocations of cmake. The [Locating Dependencies](@ref buildDependencies)
section details the variable format required to point CMake to the correct
locations. Alternatively, with interactive cmake systems such as `ccmake` or
CMake GUI, variables which are not found will be shown, allowing you to
provide them directly.

As an example, earlier versions of
[Threading Building Blocks (TBB)](https://www.threadingbuildingblocks.org/)
do not come with CMake modules or
[pkg-config](https://www.freedesktop.org/wiki/Software/pkg-config/) modules.
For OpenVDB to locate TBB, you typically need to provide this location
manually:

@code{.sh}
cmake -D CMAKE_INSTALL_PREFIX=$HOME/openvdb -D TBB_ROOT=/path/to/tbb/install ../
@endcode

Note that this is also equivalent to:

@code{.sh}
cmake -D CMAKE_INSTALL_PREFIX=$HOME/openvdb \
    -D TBB_INCLUDEDIR=/path/to/tbb/install/include \
    -D TBB_LIBRARYDIR=/path/to/tbb/install/lib \
    ../
@endcode

@subsection troubleshoot2 CMake Error ... Could NOT find XXX (Found unsuitable version: ... )

By default, OpenVDB sets a number of minimum version requires for its
dependencies. These can be found in the root CMakeList.txt or in the
[dependency table](@ref dependencies). These minimum versions either track
the oldest supported [VFX Reference Platform](https://www.vfxplatform.com/) or
are otherwise required for compatibility. Although not recommended, you can
bypass these checks with `-D DISABLE_DEPENDENCY_VERSION_CHECKS=ON` if necessary.
Note that using older or untested dependencies may produce undesired behavior.
Older versions in particular are not supported by OpenVDB.

@b Note: Boost will produce a version error in the format `Detected version of
Boost is too old.`

@subsection troubleshoot3 CMake warnings/errors in FindBoost.cmake

There are a variety of potential warnings and errors that may arise from the
version compatibility of Boost and CMake. These are related to how both Boost
and CMake have historically been kept in sync. A common warning and error
combination is:

@code{.sh}
  CMake Warning at ...  Imported targets not available for Boost version XXXXXX
  ...
  Target "..." links to target "Boost::XXX" but the target
  was not found.  Perhaps a find_package() call is missing for an IMPORTED
  target, or an ALIAS target is missing?
@endcode

OpenVDB uses [imported targets](https://cmake.org/cmake/help/latest/command/add_library.html#imported-libraries)
for all its dependencies. For imported Boost compatibility, the following
versions of CMake are required:

  - Boost 1.68, 1.69 require CMake 3.13 or newer.
  - Boost 1.70 requires CMake 3.14 or newer.

Use the above list to identify the version of CMake you require for your version
of Boost. Note that this may be implemented into the OpenVDB CMake in the future.

@subsection troubleshoot4 Detected VCPKG toolchain is using a mismatching triplet for OpenVDB build artifacts

If you are on Windows and using vcpkg, builds of OpenVDB should usually only
build the static OR shared library depending on your vcpkg triplet. This is
related to how libraries link against the Windows CRT. In vcpkg, static triplets,
such as @b x64-windows-static, will use the @b MultiThreaded (/MT) flag and
dynamic triplets, such as @b x64-windows, will use the @b MultiThreadedDLL (/MD)
flag. These flags @b must match throughout all software artifacts in your
toolchain (regardless if you are using vcpkg or not).

This warning is shown when OpenVDB detects you using either a dynamic or static
VCPKG toolchain on Windows, but have the opposite core library variant enabled.
By default, the static build of OpenVDB links against the @b MultiThreaded
(/MT) CRT and the dynamic library links against the  @b MultiThreadedDLL (/MD)
CRT. As OpenVDB configures both by default, it is typical that you may want
to disable one or the other depending on your needs.

Note that you can provide a value for `CMAKE_MSVC_RUNTIME_LIBRARY` which is a
native CMake variable to override any CRT selection done by OpenVDB.

For more information, see the following articles:
Description of CRT selection: https://docs.microsoft.com/en-us/cpp/build/reference/md-mt-ld-use-run-time-library
In depth descriptopn of the CRT on Windows: https://docs.microsoft.com/en-us/cpp/c-runtime-library/crt-library-features
Related errors: https://docs.microsoft.com/en-us/cpp/error-messages/tool-errors/linker-tools-error-lnk2038
`CMAKE_MSVC_RUNTIME_LIBRARY` docs: https://cmake.org/cmake/help/latest/variable/CMAKE_MSVC_RUNTIME_LIBRARY.html

@subsection troubleshoot5 Unexpected value for the Windows CRT with target build artifacts.

On Windows, it is typical for static builds to link to static libraries and
dynamic builds to link to dynamic library variants. This is not related to the
libraries themselves, rather it is due to the way that all libraries used within
a specific toolchain must use the same version of the CRT. The rule of thumb is
to configure static builds against the static CRT and dynamic builds against
the dynamic CRT.

This warning is shown if you have provided a value for the CMake variable
`CMAKE_MSVC_RUNTIME_LIBRARY`, but this value is the opposite of what's expected
for a target library.

Note that there are some cases where it makes sense to link static builds of
OpenVDB against the dynamic (/MD) CRT. However, unless you are confident in your
usage, it is strongly encouraged to match the selection against your desired
build type.

For more information, see the following articles:
Description of CRT selection: https://docs.microsoft.com/en-us/cpp/build/reference/md-mt-ld-use-run-time-library
In depth descriptopn of the CRT on Windows: https://docs.microsoft.com/en-us/cpp/c-runtime-library/crt-library-features
Related errors: https://docs.microsoft.com/en-us/cpp/error-messages/tool-errors/linker-tools-error-lnk2038
`CMAKE_MSVC_RUNTIME_LIBRARY` docs: https://cmake.org/cmake/help/latest/variable/CMAKE_MSVC_RUNTIME_LIBRARY.html

@subsection troubleshoot6 error LNK2038: mismatch detected for 'RuntimeLibrary'

A build artifact of OpenVDB has been linked against a dependency which uses a
different version of the Window CRT. See the [above section](@ref troubleshoot5)
on dealing with CRT selection for static and dynamic library builds on Windows.

*/