To run Mentor examples on /afs/cern.ch/sw/lhcxx/specific/redhat61/OpenInventor/2.5/src/examples/Mentor/C++/ you need to define the appropriate libraries with:

    setenv LD_LIBRARY_PATH /afs/cern.ch/sw/lhcxx/specific/redhat61/egcs_1.1.2/OpenInventor/2.5/lib/

If you want to compile them than you need this Makefile:

    # Rename this file Makefile

    # GNU makefile
    # Execute with gmake on Linux and Unix systems
    # Sometimes gmake is linked to make (ln -s gmake make), in which
    #   case, make and gmake work equally well
    OIVHOME =  /afs/cern.ch/sw/lhcxx/specific/redhat61/gcc-2.95.2/OpenInventor/2.6

    # Makefile for OpenInventor 2.6 (TGS) on LINUX

    OGLHOME = /afs/cern.ch/sw/lhcxx/specific/redhat61/Mesa/3.2
    MOTIFHOME = /usr/local
    CC	     = /usr/local/gcc-alt-2.95.2/bin/gcc -D_GCC_
    C++          = /usr/local/gcc-alt-2.95.2/bin/g++ -D_GCC_
    MOTIFINCLUDES= -I$(MOTIFHOME)/include -I/usr/X11R6/include  -I/usr/include/g++
    XINCLUDES    =
    GLINCLUDES   = -I$(OGLHOME)/include
    MOTIFLIBS    = -L$(MOTIFHOME)/lib -L/usr/X11R6/lib -lXm -lXt -lXi -lXext -lX11
    GLLIBS       = -L$(OGLHOME)/lib -lGLU -lGL -lGLw
    SYSTEM_LIBS  = -lstdc++ -lm -ldl
    BUILDSO      = ld -shared

    OIV_INCLUDES = -I$(OIVHOME)/include
    #include $(OIVHOME)/config/Inventor.mak

    INVENTORLIBS = -L$(OIVHOME)/lib -lInventorXt -lInventor -limage

    C++FLAGS = $(C++DEBUGFLAGS) $(INCLUDES) $(DEFINES)
    LOCAL_LIBRARIES = $(INVENTORLIBS) $(GLLIBS) $(MOTIFLIBS) $(SYSTEM_LIBS)
    INCLUDES = $(OIV_INCLUDES) $(GLINCLUDES) $(MOTIFINCLUDES)  $(XINCLUDES)

    #----------------------------------------------------------------------

    EXEC = oiv_Cver1
    OBJS =  oiv_Cver1.o

    #----------------------------------------------------------------------

    .SUFFIXES: .o .cxx
    .cxx.o:
    	$(C++) -c $(C++FLAGS) $<

    all:: $(OBJS)

    PROGRAM = oiv_Cver1

    clean::
    	$(RM) $(OBJS)

    .SUFFIXES: .o .C
    .C.o:
    	$(C++) -c $(C++FLAGS) $<

    all:: oiv_Cver1

    $(EXEC): $(OBJS)
    	$(C++) -o $@ $(OBJS) $(LDLIBS) $(LOCAL_LIBRARIES)

    clean::
    	$(RM) $(PROGRAM)

    default:: all

with this definition of $LD_LIBRARY_PATH:

    >setenv LD_LIBRARY_PATH /afs/cern.ch/sw/lhcxx/specific/redhat61/OpenInventor/2.6/lib:/afs/cern.ch/sw/lhcxx/specific/redhat61/Mesa/3.2/lib