Thank you so much for your reply.
My sample point spacing is around 20m to 30m spacing. I would like to create tunnel filtered model based on the 3D lithology model. If the spacing is big, the tunnel filtered model is quite rough (can't get smooth circular shape or tube). The tunnel length is about 5km and our initial aim is to create a continuous tunnel filtered model for the whole length. Thus, I would like to know is that possible if I model multiple smaller dimension model, can these models be combined into a single model and use for the tube filter function.
Thank you very much for your advice again.