I have a list of {x,y,z} pairs representing points in $R^3$. For every unique value of *z* there are many {x,y} pairs defining a polygon/contour in that particular *z*-plane. My dataset looks like this:

    Input:= Take[ptv, 3]
    Output= {{61.52, -217.26, -80}, {63.48, -217.64, -80}, {65.43, -217.64, -80}}

These are the coordinates of points residing on the z=-80 plane. There are other pairs for z=-75, z=-70, etc. Therefore `ptv` is of the form:

ptv: {{$x_1$,$y_1$,-80}, {$x_2$,$y_2$,-80}, ..., {$x_k$,$y_k$,-80}, ..., {$x_1$,$y_1$,-75}, ...}}

My **goal** is to create a 3D surface where:

1. the points in every *z*-plane are connected into a polygon/contour and
2. the points in every *z*-plane are connected with their neighbors in the immediately above and below plane.

Currently, I have achieved *1.*, via:

    Graphics3D[Line[ptv], Point /@ ptv}]

The result looks like this: 
![Plot1][1]

If I, instead, use:

    ListSurfacePlot3D[ptv, AxesLabel->{"x","y","z"}]

 I get some ugly artifacts (edges at the boundaries of the volume) as shown here: 
![Plot2][2]

Whereas, I was expecting a more "smooth" surface without any "openings". Any hints on:

1. Whether `ListSurfacePlot3D[]` is the proper function to use (i.e. in the documentation it is mentioned that `ListSurfacePlot3D[]` may "fold" over; perhaps this is why I'm experiencing these ruffles?) or
2. What other alternatives are there to consider ?


  [1]: https://i.sstatic.net/IF5Gk.png
  [2]: https://i.sstatic.net/SMwHg.png