FIX: we *need* OPENGL_INCLUDE_DIR, since OPENGL_INCLUDE_PATH is *not* in the cache

vtkCMakeOptions.cmake

@@ -125,6 +125,12 @@ IF(CMAKE_COMPILER_IS_GNUCXX)
   ENDIF(WIN32)
 ENDIF(CMAKE_COMPILER_IS_GNUCXX)
 
+IF (OPENGL_INCLUDE_DIR)
+  INCLUDE_DIRECTORIES(${OPENGL_INCLUDE_DIR})
+ENDIF(OPENGL_INCLUDE_DIR)
+
+# This one because OPENGL_INCLUDE_PATH is also defined for backward compatibility
+
 IF (OPENGL_INCLUDE_PATH)
   INCLUDE_DIRECTORIES(${OPENGL_INCLUDE_PATH})
 ENDIF(OPENGL_INCLUDE_PATH)