I’m trying to extrude a portion of a hexagonal prism so that it looks like this.
Unfortunately, when I move the selected plane surface, undesirable morphing occurs.
I made the desirable output by exporting the 3dm file to Sketchup and pushing the surfaces upwards.
How can I achieve the same in Rhino?
You can use direct editing on many Rhino geometries by holding control + shift and simultaneously clicking on a surface for example. Or select one surface after another, while holding control + shift
Use the gumball to scale with factor 0 to make it flat.
Use the gumball to move your geometry or parts of it to a certain height
Not sure if your bottom surface needs the division. You can get rid of it with the command
If instead you just want a clean surface instead of the many isocurves, you can delete it and type
cap to build a fresh surface.
Moving the doodled faces while holding ctrl+shift gives warping. I want to have this type of geometry
Even in this photo warping is happening which is not required.
Select the 3 bottom faces and use ExtrudeSrf with the DeleteInput option set to Yes. Do not use the Gumball to do this.
Sorry I was giving you instructions on how to fix the warped surface