g=f(x,y,z)=ae−r−c≥0,where r=(x−xb)2+(y−yb)2+(z−zb)2 g=f(x,y,z)=ae^{-r}-c\ge 0, \quad\text{where }r=(x-x_b)^2+(y-y_b)^2+(z-z_b)^2 g=f(x,y,z)=ae−r−c≥0,where r=(x−xb)2+(y−yb)2+(z−zb)2或者 g=f(x,y,z)=1r+1,where r=(x−xb)2+(y−yb)2+(z−zb)2 g=f(x,y,z)=\frac{1}{r+1}, \quad\text{where }r=(x-x_b)^2+(y-y_b)^2+(z-z_b)^2 g=f(x,y,z)=r+11,where r=(x−xb)2+(y−yb)2+(z−zb)2