Hi Pilou, so here is an example that has that kind of angle in it:






It follows really the same pattern as what I sent to you in e-mail (as shown in the previous post above), just instead of doing an extrusion for the side piece, I did a sweep instead, to give it that bulbous angle that you wanted now.

You can easily make variations in a pattern by adjusting just one piece like this, for example use a sweep instead of an extrude for one step to customize the shape.

I've attached an example model file RoundedSlab.3dm


This will come together actually very quickly with only a few curves to build it.

I started it by drawing a Rectangle (by center point) in the Top view with the Rounded corners option to make this:



Now switch to the Front view and draw a curve that has the kind of angle that you want in it like this:



These 2 curves are arranged in proportion to one another like so:



Now you pick the small one and run Construct / Sweep to build a the side wall surface like this:



To give it a more rounded overall shape I then drew 2 crossing curves like this:



And then did a Sweep again with one of those as the profile and the other as the rail to give a kind of gently rounded top cap piece:



You can skip this if you want and just use a totally flat cap piece instead, a flat piece can be filled in by just selecting the sweep and doing Construct / Planar to fill in the open planar ends.

But with the custom slightly rounded cap, I then moved it downwards so it intersected the side wall parts like this:



Then I selected both surfaces, and used Edit/Trim and discarded the unwanted parts. Instead of Trim you could also make the sweep part into a solid by using Planar as described above, and then do a boolean with that solid and use the rounded cap as the cutting surface. But when you just have open surfaces and not solids then you use Trim instead of booleans for cutting things.

After trimming the excess pieces off, then use Join to glue them together into one connected piece which results in this:



Then use Fillet to round off the top edge, here I used the G2 blend option in Fillet and adjusted the slider slightly to make it have less bulge:




So notice that one of the key things is that the pieces come together in a sharp corner initially and then I use fillet to produce the final rounding to smooth it all out - that's kind of the key construction technique for stuff like this with regular NURBS tools. It makes it much easier to construct when you do not initially worry about getting perfect smoothness and instead focus on making the overall larger forms correct, and let Filleting add in smoothness at the end to places where the form switches from one kind of overall shape to another.

- Michael