3D Surface Contour - Extract Selection

Hi,
I am trying to extract coherent structures with alpha >= 0.5. But I am getting those 3D surfaces disrupted as you can see in the fig I attached. I understand why it’s happening, its because some of the grid points might not satisfy the extraction condition. Is there a way to fix it or any other approach to extract those 3D surfaces?
Thank you for the help!

Hi,

It may be adjusted in the All Scalars option of the Threshold filter.