### **OptParameters** * * * * * **Description**： Define some parameters of the BESO algorithm. **Input**： S: Sensitivity. Presets can be selected from PreProcessing. ~~~ In short, sensitivity is the basis for the increase and decrease of the unit. At present, the strain energy density and the Mises stress can be selected. When the unit volumes are all the same, the calculation results of the strain energy density or the Mises stress are the same, but the unit sizes are generally different. In order to consider the influence of the unit volume, the strain energy density is selected. ~~~ vf: Constrained volume fraction. ~~~ The constrained volume fraction is the percentage of the volume of the material area to be retained in the original design area (0-1). This value cannot be too small. Otherwise, the material is not enough to establish a structure. The calculated structure is not established, and the calculation will not be convergence. ~~~ ert: Evolution rate. ~~~ Evolution rate is the volume percentage of material cut at each step. (recommended 0.01-0.05) ~~~ rmin:过滤半径。（默认为3倍的网格） ~~~ It can be understood that the center of the i-th unit is the center, the radius is Rmin (the three-dimensional is the ball), and the sensitivity of the i-th unit is determined according to the distance between the inner unit and the i-th unit. ~~~ **Output**： Paras: Parameter set.