Can anyone advise me on the recommended approach to create a kink in a boundary edge curve of a single span surface without compromising the G2 continuity of the surface and such that, once the kink is inserted, you can then move the surface CVs around without compromising the G2 continuity of the surface?
Here is what I did:
Added a point on the edge where I wanted the kink
inserted a kink on surface in selected UV direction, snapping to the point. This step added several control points and iso-lines, which I guess are all knots. I think it converts it to a 2-span surface, “joined” at the kink iso-line.
Then I moved the control points using the gumball to develop a suitable shape that gave me the desired kink in the edge curve
But, if you look at the image, the kink line on the surface is visible in the render.
If I execute the “converttosinglespan” command, which splits the surface at the kink, and then go through a match surfaces exercise, the kink in the boundary edge curve gets blended out.
So, is there some way end up with a “smooth” surface but leave the boundary edge kink?
Hello- I am not quite getting what you are after - can you post a file with that object? It seems you want a kink and not at the same time… is the idea to kink the edge only but not the surface? In that case you can ExtendSrf to make the surface over sized (if needed - depends on which way to kink) and then trim with a kinked curve.
Look closely at the image sent previously and you will see the discontinuity in the tangency running down from the edge kink point. You may need to zoom in on the image.
I understand about using a trim. But, I am trying to end up with an untrimmed (ideally, single span) surface so I am able to move the boundary edge CVs directly to model what I want to see at the surface edge directly and all the advantages of untrimmed, single span surfaces.
I tried using refit trim, but that seemed to get me back to a similar set of geometry.
Maybe it is the match surfaces command that I don’t quite understand… I want the match surface to just adjust the joined edges, but leave the top edge curve kink (tangency & curvature discontinuity) alone.
This must be a common issue in car body and aircraft design with a well developed way of generating the surface geometry to get an inside “corner” with a minimum number of patches. I just have not found a discussion anywhere that describes a way to solve it.
For a surface with a kinked edge, the surface has G2 continuity except at the kink, then control points can be stacked at the the kink location on the edge. “Stacking control points” means dragging control points so that they coincide. The number of control points which need to be stacked equals the degree of the curve.
Control points can be added for stacking using InsertKnot which maintains the shape of the surface until control points is moved. The knots need to be inserted at distinct locations, and then the control points stacked at the desired location of the kink.
