Fix VTK build error for certain environments

modules/odm_georef/CMakeLists.txt

@@ -12,6 +12,7 @@ find_library(PROJ4_LIBRARY "libproj.so" PATHS "/usr/lib" "/usr/lib/x86_64-linux-
 add_definitions(-Wall -Wextra -Wconversion -pedantic -std=c++11)
 
 # Find pcl at the location specified by PCL_DIR
+find_package(VTK 6.0 REQUIRED)
 find_package(PCL 1.8 HINTS "${PCL_DIR}/share/pcl-1.8")
 
 # Find OpenCV at the default location

modules/odm_meshing/CMakeLists.txt

@@ -8,6 +8,7 @@ set(PCL_DIR "PCL_DIR-NOTFOUND" CACHE "PCL_DIR" "Path to the pcl installation dir
 add_definitions(-Wall -Wextra)
 
 # Find pcl at the location specified by PCL_DIR
+find_package(VTK 6.0 REQUIRED)
 find_package(PCL 1.8 HINTS "${PCL_DIR}/share/pcl-1.8")
 
 # Add the PCL and Eigen include dirs. 

modules/odm_orthophoto/CMakeLists.txt

@@ -9,6 +9,7 @@ set(OPENCV_DIR "OPENCV_DIR-NOTFOUND" CACHE "OPENCV_DIR" "Path to the OPENCV inst
 add_definitions(-Wall -Wextra)
 
 # Find pcl at the location specified by PCL_DIR
+find_package(VTK 6.0 REQUIRED)
 find_package(PCL 1.8 HINTS "${PCL_DIR}/share/pcl-1.8" REQUIRED)
 
 # Find OpenCV at the default location

modules/odm_slam/CMakeLists.txt

@@ -8,6 +8,7 @@ set(OPENCV_DIR "OPENCV_DIR-NOTFOUND" CACHE "OPENCV_DIR" "Path to the opencv inst
 add_definitions(-Wall -Wextra)
 
 # Find pcl at the location specified by PCL_DIR
+find_package(VTK 6.0 REQUIRED)
 find_package(PCL 1.8 HINTS "${PCL_DIR}/share/pcl-1.8" REQUIRED)
 
 # Find OpenCV at the default location