Unexpected Results with Insert Point Tool

[aaronsgreen]

I've created a hexagonal nut in sculpt mode from a sketch and 2mm extrusion, but I'm having an error with the T-spline surface; I don't even know what that means. As you can see, I've subdivided a hexagonal sketch extrusion, deleted the edges running out to the corners, then inserted simple points across the hex corners. This is so the surface matches the real nut when I squash the corners. For some reason, the subdivision edges in the centre go crazy after I insert the points.

This is the error that's thrown at some point, so I can't transfer it to model mode.

If I delete the crazy edges, the smoothing levels out to how I hoped it would be, but I'm missing one corner to get this.

If I try to insert point with the simple option it looks fine in the preview, but if I add it in it goes back to the first image; crazy lines.

If I try to use the exact option for insert point, it doesn't even give me the option to select vertices, and I can only put one point mid edge; useless.

Any help would be appreciated, as I've spent 4 days on Fusion so far. I have several years experience in 3ds Max, but not much of it translates to this. It's fairly intuitive, but these things do my head in.

[colin.smith]

Hi @aaronsgreen, 

I'm not sure how you closed up the top of the hex extrusion.  I would suggest something like the image below. 

Hope that helps, 

Colin

[aaronsgreen]

I closed the top using the Fill Hole tool.

I wrote another post about T-Spline has an invalid surface error that relates to this. It turns out the corners sections I create are invalid triangles, and I was told by someone else never to create triangles with T-splines. I don't understand why this is a rule, or why it's not prevented if it's true. If you use the Fill Hole tool, it automatically creates triangles if you use the exact option with creased edges.

I also discovered that Fusion puts 'T' symbols on vertices that are related to invalid surfaces. If I go to the Repair Body tool, I can select the 'T' symbols and it converts them to Star symbols, validating the surfaces. Then I can finish the form and go to model mode.

.

I don't understand any of this, but have managed to get by