Build instructions in Readme don't work

Comienza con README.md y la integración de CMake utilizada cuando el módulo se copia en la carpeta Remote de VTK. Reproduce la configuración de Windows VTK 9.0.1, comprobando HoloPlayCore_INCLUDE_DIR, HoloPlayCore_LIBRARY, Qt5_DIR y VTK_GROUP_ENABLE_QT. Se considera terminado cuando README describe correctamente la preparación necesaria y la compilación documentada produce el módulo.

I tried following the provided instructions for building VTK 9.0.1 with support for Looking Glass devices enabled by this project, but I wasn't able to make them work. I followed the instructions detailed here:

• https://github.com/Kitware/LookingGlassVTKModule/blob/master/README.md
• https://docs.lookingglassfactory.com/developer-tools/index-2

In the end, I was able to figure out how to properly build VTK 9.0.1 with LookingGlass support following a rather different procedure detailed below. So either the README needs to be amended or something is broken in the CMake scripts.

Setup

• Windows 10
• Visual Studio 2015
• VTK 9.0.1
• CMake 3.20.3
• Python 3.9.0
• Qt 5.11.0

Things that I tried and didn't work

• adding VTK_MODULE_ENABLE_VTK_RenderingLookingGlass as a BOOL entry in CMake-gui 3.20.3 and enabling it
• adding VTK_MODULE_ENABLE_VTK_RenderingLookingGlass as a STRING entry in CMake-gui 3.20.3 and setting its value to ON
• adding the environment variable VTK_MODULE_ENABLE_VTK_RenderingLookingGlass=ON in CMake-gui 3.20.3
• modifying CMakeCache.txt and adding the following lines:

//Enable the VTK::RenderingLookingGlass module. 
VTK_MODULE_ENABLE_VTK_RenderingLookingGlass:BOOL=ON

• invoking cmake directly from the command line inside the VTK source root directory

cmake -DVTK_MODULE_ENABLE_VTK_RenderingLookingGlass:BOOL=ON -S . -B Build -G "Visual Studio 14 2015" -A x64

What actually worked

• clone the repo at https://github.com/Kitware/LookingGlassVTKModule
• copy the contents of the cloned repo LookingGlassVTKModule to the Remote folder in the VTK source tree
• configure the CMake project for VTK for Visual Studio 2015 and set the architecture option to x64
• set the variable HoloPlayCore_INCLUDE_DIR to the include path of the HoloPlay SDK
• set the variable HoloPlayCore_LIBRARY to point to the pre-built static library of the HoloPlay SDK for Windows
• set VTK_GROUP_ENABLE_QT to YES
• set Qt5_DIR to the location of the CMake folder of my installation of Qt
• set PYTHON_VERSION to 3
  check VTK_WRAP_PYTHON
• configure again
• generate the project files
• open the main solution in Visual Studio 2015
• build the project for release

Notes
I did a grep on the entire source tree of VTK and I found no mention of the word LookingGlass, so my expectations was that by setting the variable VTK_MODULE_ENABLE_VTK_RenderingLookingGlass to ON, CMake will reference an online registry to find this repository, download the code and and update the CMake configuration with the variables HoloPlayCore_INCLUDE_DIR and HoloPlayCore_LIBRARY required to generate a proper output. Clearly my assumption was incorrect and it seems that developers are required to copy at least some files from this repository to the VTK source tree. Figuring out how to do so without being intimately familiar with VTK's innerworkings is not easy. Please provide more details on how to prepare for a build in the README.