Hi Curious, so for your gold shape that's pretty difficult. One of the main ways to build a separate piece and have it appear seamless to an existing surface is to have some space between them and use Construct > Blend to make a new surface between them that is smooth to either side. But this becomes difficult if you're trying to make things smooth between 2 different directions at a corner.
To avoid that kind of blend at a corner problem it can work to slice things up so that there is a smooth shape there instead of a corner.
Here's how that would go in your case here.
First you need to get a surface built that touches the sides you're going to want to be smooth but has the curled in part. There are several possible ways that you could approach this, one way that I wanted to try was to model the curl coming off of a plane instead of directly "in place" on your model and then map it onto your main shape using Transform > Deform > Flow with the "projective" option. That looks like this:
I took 2 straight lines from your profile curves, and then drew in 2 curves like this for the sunken corner:
Then Construct > Network to build a curled-corner surface:
Then added a plane surface:
Now Transform > Deform > Flow with the "Projective" option can push the curled surface onto the main shape and it will have the same relation to the main shape as the starting shape has to that base plane surface:
The part that's good about using Flow to generate the surface is it is kind of easier to reason about and to adjust the generating shape that comes off of a flat plane rather than trying to draw them directly in place on a curved surface.
So now the tricky part is that the new surface is not going to be totally smooth at its boundaries to the main shape. It will touch the main shape but not have the same surface curvature where it touches so there will be a slight crease visible between them if you were to just cut out a rectangle hole.
To make things have a smooth connection you can open up some space between them and use Construct > Blend to put in a blend surface. But a blend surface is a 2-sided thing. So to make it possible to put in one blend there between them the space that you open up would need to look something like this:
That's done by trimming the main body with a profile like this:
And trimming the curled in surface with a profile like this:
That then gives this area to put in a blend surface:
This type of Trim & Blend surface modeling is a pretty advanced area of NURBS modeling, it takes a lot more time to learn than stuff like mechanical parts. But it's a method that can work for making some local different shaped feature in the middle of an existing surface.
- Michael
