用optistruct进行模型的形貌优化分析，出现如下两个错误，求大神解答？ 100

 A fatal error has been detected during input processing:

  *** ERROR #  81 ***

  No topography data can be generated for a DTPG data # 1.

  The buffer zone is too large, or cannot be established.

  There might not be a non-design region attached to the

  design region.

  *** ERROR #  79***

DTPG data does not create any DVGRID data.

there are no free referenced GRIDs.

there may be no elements associated with the PSHELL data.

LOAD or BOTH may be specified and all grids may be loaded.

BC,SPC,or BOTH may be specified and all grids may be SPCed.