Lofting With Flat Sides - Triangular faces not doing the thing

[u/Significant-Let3635]

Grey "Curve" front and center

I have a problem where if I select specifically the diagonal grey "Guide Curve" above where it will simply refuse to make the loft.

I have 2 separate 3D sketches for the guide curves, one that matches the exact points from top to bottom (yes, vertices are the same between top and bottom) and one that matches some diagonals, because this thing is planned to be made out of plywood sheets. A such, due to there being a rotation and angle between the two profiles, the faces are curved.

This "guide Curve" solution has successfully made all other faces into triangles, but this one face (not specifically, it could move around depending on where I start, what the weather is, and how soft my left index finger is on any particular day).

I would like to know if I am missing something? Using the wrong tool or what?
I would like a thin-wall section here, so ideal seems to be the thin wall option in boss/base loft.

What I have tried:
- 1, 2, or 3 different 3d guide sketch
- A combination of open or closed guide loops
- Both Lofted boss/base as well as lofted surface, and then adding offset faces etc to get the wall thickness
- thin-wall and non-thinwalled
- Loft it with the problem, and then delete a face and add in another loft afterwards (has a whole heap of other problems, some of which seem to duplicate)
- Open and closed groups for the guide lines (though I may be doing this wrong!)

More info in the screenshots below, I guess:

Grey "Curve" Selected, now results in invalid geometry

result when I build with the particular diagonal unselected

wireframe of the successful but with 1x curved face.

Error for that guide curve.

Natural error when I try accept with an invalid guide curve.

[u/CriticismAccording71]

is that guide curve one continuous sketch?

try building it up as separate filled surfaces. Use selection manager and select 3 lines at a time to build up each triangular face. There is too much going on here for SW to get it right in one action.

Use the filled surface tool, and build it up one by one. Once you've done this, knit the surfaces and thicken. Or thicken each face independently if you want separate bodies.

Hope this helps / answers what you were trying to achieve

[u/Significant-Let3635 → u/CriticismAccording71]

I guess what confuses me is that it does the whole thing, until literally the last guide-line..

I have used surfaces as a stop-gap, but.. it feels flimsy..

Thank you

Tried a bunch of different sketches, some open, some continuous some not

[u/CriticismAccording71 → u/Significant-Let3635]

I personally wouldn't attempt to do something like this any other way. The way I understand things, any loft or boundary operation works best with 4 sided faces. From what I can see, you're taking two 6 sided shapes as your start and end profiles, and where a standard loft would then create 6x 4 sided faces to join them, you want to join them with a number of triangles (plus one four sided shape, from what I can see). Using a single guide curve to do this in one operation is a bit of a non starter.

Get comfortable with surfacing, it opens the door to many modelling techniques.

Let me know if you manage to make your part!

[u/Significant-Let3635 → u/CriticismAccording71]

The reason for the triangles is to remove the curved sides. The 4-sided shape was the one giving an issue. Weirdly enough if I deselect all other guides and just select the "problem" one, it'll also fail. Regardless of where the problem one is from

Actually... Saying that.... I got it right before.... How on earth did I get it right before....