Pass `VTK_DIR` to SimMedTK build from superbuild.

If `SimMedTK_VTK_DIR` is defined, its value is used for `VTK_DIR`.
Otherwise, we ask CMake to find VTK and pass whatever it returns
from the superbuild to the SimMedTK build.

CMake/SuperBuild/SuperBuild.cmake

@@ -164,6 +164,15 @@ endif(WIN32)
 #
 SET(proj SimMedTK-Configure)
 
+if (NOT SimMedTK_VTK_DIR)
+  find_package(VTK REQUIRED)
+  mark_as_advanced(SimMedTK_VTK_DIR)
+  set(SimMedTK_VTK_DIR ${VTK_DIR})
+endif()
+list(APPEND SimMedTK_SUPERBUILD_CMAKE_OPTIONS
+  "-DVTK_DIR:FILEPATH=${SimMedTK_VTK_DIR}"
+)
+
 ExternalProject_Add(${proj}
   DOWNLOAD_COMMAND ""
   CMAKE_GENERATOR ${gen}
@@ -171,6 +180,7 @@ ExternalProject_Add(${proj}
   CMAKE_ARGS
     ${CMAKE_OSX_EXTERNAL_PROJECT_ARGS}
     ${CMAKE_MSVC_EXTERNAL_PROJECT_ARGS}
+    ${SimMedTK_SUPERBUILD_CMAKE_OPTIONS}
     -DSimMedTK_SUPERBUILD:BOOL=OFF
 #     -DSimMedTK_SUPERBUILD_BINARY_DIR:PATH=${SimMedTK_BINARY_DIR}
 #     -DSimMedTK_INSTALL_BIN_DIR:STRING=${SimMedTK_INSTALL_BIN_DIR}

CMakeLists.txt

@@ -169,6 +169,7 @@ find_package(Assimp REQUIRED)
 find_package(Eigen3 REQUIRED)
 find_package(VegaFEM REQUIRED CONFIG)
 find_package(ThreadPool REQUIRED)
+find_package(VTK REQUIRED)
 
 if(SimMedTK_USE_OCULUS)
   find_package(Oculus REQUIRED)

VtkRendering/CMakeLists.txt

-
-find_package(VTK REQUIRED)
-
 include(${VTK_USE_FILE})
 
 simmedtk_add_library(VtkRendering