have gui be off by default in example viewer, same as the sg version
have gui be off by default in example viewer, same as the sg version

ospray/OSPRay,ospray/OSPRay,MengjiaoH/ospray,MengjiaoH/ospray,MengjiaoH/ospray,MengjiaoH/ospray,wilsonCernWq/ospray,wilsonCernWq/ospray,ospray/OSPRay,wilsonCernWq/ospray,MengjiaoH/ospray,ospray/OSPRay