Locking elements of a surface/control point manipulation

I’m currently working in Rhino for Mac but have access to Rhino 5 for Windows as well.

I’m working with double curved panels that fit into a larger frame. For this reason, the edge can’t move as I manipulate the surface. I want the middle of the surface to bulge out (like a cushion, or pocket of fluid). I have tried rebuilding and manipulating the number of control points. Either the edge moves or I can’t get a smooth bulge in the middle. I’ve also tried in Maya with sculpting and soft selection, but the edge moves there as well. Any ideas?

I uploaded a photo of one of the panels. They were originally trimmed from a torus, which is why the control points are this way. I’ve already shrunk the surface.

I think what you want isnt possible by transforming this surface.
The edges will ALWAYS move. You need to recreate the surface for doing what you want.

Thanks for the quick reply Jordy!

I was wondering if that might be the case…I’m currently attempting to create a new surface with NetworkSrf, no luck so far. If you know of a better alternative, suggestions are welcome. Thanks again!

You could try to offset the surface and trim it to be the size the top of the cushion would be. Cut a hole in the original surface that is bigger than the offset surface (probably just the edge of the original surface offset a small amount inwards). Then blend the two surfaces.

gamble around with loft and patch and history