Cannot call function "rendering::Scene::VisualAt", undefined symbol?

edit

Whenever I call the function "rendering::Scene::VisualAt" or "Camera::ZValue", it complains:

gzserver: symbol lookup error:
catkin_ws/devel/lib/librand_camera.so:
undefined symbol: _ZN6gazebo9rendering6Camera6ZValueEii

in which "rand_camera" is the my project name. Anyone knows how to solve this? I really appreciate it!!

------------------- Details---------------------

Gazebo version: 7.1

CMakeLists:

cmake_minimum_required(VERSION 2.8.3)
project(rand_camera)

find_package(catkin REQUIRED COMPONENTS
  gazebo
  gazebo_dev
  roslib
  roscpp
  geometry_msgs
  std_srvs
  std_msgs
  gazebo_msgs
  gazebo_ext_msgs
  gazebo_plugins

)

find_package(OpenCV REQUIRED)

find_package(Boost REQUIRED COMPONENTS thread)

catkin_package(
  LIBRARIES
    rand_camera

  CATKIN_DEPENDS
    roslib
    roscpp
    gazebo_ros
    geometry_msgs
    std_srvs
    std_msgs
    gazebo_msgs
    gazebo_ext_msgs
    gazebo_plugins
)

include_directories(
  include
  ${Boost_INCLUDE_DIRS}
  ${catkin_INCLUDE_DIRS}
  src/skyx/include
  ${OGRE_INCLUDE_DIRS}/Paging
  )

link_directories(${catkin_LIBRARY_DIRS})

# link_directories(${GAZEBO_LIBRARY_DIRS})


set(cxx_flags)
foreach (item ${GAZEBO_CFLAGS})
  set(cxx_flags "${cxx_flags} ${item}")
endforeach ()

set(ld_flags)
foreach (item ${GAZEBO_LDFLAGS})
  set(ld_flags "${ld_flags} ${item}")
endforeach ()

## Plugins
add_library(rand_camera src/RandCamera.cpp)
add_dependencies(rand_camera ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})
target_link_libraries(rand_camera ${catkin_LIBRARIES} ${Boost_LIBRARIES} ${TinyXML_LIBRARIES} ${OpenCV_LIBS} ${GAZEBO_LIBRARIES})

# Install Gazebo System Plugins
install(TARGETS rand_camera
  LIBRARY DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
  )