MACRO(USE_SIXENSE)
  FIND_PACKAGE(Sixense)
  IF ((NOT SIXENSE_FOUND) AND (${ARGC} LESS 1))
    USING_MESSAGE("Skipping because of missing SIXENSE")
    RETURN()
  ENDIF((NOT SIXENSE_FOUND) AND (${ARGC} LESS 1))
  IF(NOT SIXENSE_USED AND SIXENSE_FOUND)
    SET(SIXENSE_USED TRUE)
    INCLUDE_DIRECTORIES(SYSTEM ${SIXENSE_INCLUDE_DIR})
    SET(EXTRA_LIBS ${EXTRA_LIBS} ${SIXENSE_LIBRARIES})
  ENDIF()
ENDMACRO(USE_SIXENSE)