Need help modeling convex triangle

[Thais_Gazzillo_Zuche (Thais Zuchetti)]

Hello! I am trying to recreated digitally some existing ornaments for a friend’s balcony and I am very stuck with one part and maybe someone could help!
Basically the shape is an 8-sided dome that starts from a 4-sided base (an octagon emerging from a cube)

My trouble here is that on the corners, I am supposed to connect the point on the edge of the cube to the dome shape, creating a triangular convex surface (?)

This is what I have now:

this is how the thing has to look like:

I tried using loft, sweep, sweep point to curve
I’m not very pro on rhino, so I guess I am definitely missing something

If someone could give me a light would be amazing!
Thank you all!

I will drop the file as well
Ornament4.3dm (4.1 MB)

[Brenda]

It’s a little late for me, so the quality is poor, but this might be a start…

I think that just adding a filleted section would be problematic because the part you would run nearly coplaner to the part that is there.

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So, the part underneath needed to be removed, or really the affected face needs to be rebuilt.
What I did was:

I copied everything.

I exploded the finial.

I created 2 curves by copying the side edges of the finial section I moved out.

Using your height reference line, I split the lines I created, using the point option.

I curve-matched the curves of the lines you intended to be the fillet edges, to the copied edge curves.

I joined the fillet curves to the edge curves.

I used EdgeSrf to create the long surface from the result edge curves.
(Sweeping and lofting likely won’t work.)

For each side, I used the remaining curves to edge curve the end cap.

There still may be gotchas when assembling it, but this may work, though you have to be more careful than I am, while trying to stay awake.

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Also, it looks like in the photo, that the main sides of this thing look kind of like a pointy oval.

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If you have one of these swoopy faces, you can also make it wider, and then array polar, and then use them to trim each other and make a solid. Surfaces can overlap while creating a solid, as long as the result would be airtight, and it’s cool to watch.

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You can also make a subtraction tool using one of these swoopy faces and a few more surfaces, and then subtract the tool from the post, or whathave you, and keep rotating it between subtractions, or perhaps just do a boolean 2 objects using the surface and the solid post.

[Thais_Gazzillo_Zuche (Thais Zuchetti)]

Hey Brenda!
Thank you so much for holding up awake and help me out!
There were some gotchas indeed, but what you did really helped me out on a way to start this thing!

thanks thanks

[pascal (Pascal Golay)]

Hello - I think the simplest way to do this is to flatten the edge curves in the axis of the surface:

then extrude the curve:

and then trim with the original edge curves:

Or explode the edge curves and simply loft across.

-Pascal