SubD crossover geometry best practices?

[victorlin (Yu Chieh (Victor) Lin)]

I want to get some advise on how best to model a crossover geometry in SubD, something like the screenshot below:

The idea is that I want a smooth transition without the hole in the splitting region, I’ve tested a few different ways to do the transition, but always get some kind of pinching, a hole, or self-intersecting model.

I’d like to know which one would be the best practice in regards to subd modeling, and if there are any other ways of achieving this.

test models:
SubD-Crossover.3dm (252.7 KB)

thanks

[Tom_P]

I would recommend to start with a face-layout, that has a nice stripe / loop of faces (violett) around the cut.
This will give you all necessary control to shape the cut as you like.
And avoids n-gons and star-points at the cut.

SubD-Crossover_TP02.3dm (3.2 MB)

(EDIT: new file, minimal update to have nicer top-view)

you can start with Version (5) of your file, and use _subDivide.
Then delete some of the new edges and _slide to get the layout from the screenshot.
… for sure there is may different approaches to get it.

[victorlin (Yu Chieh (Victor) Lin)]

this is indeed cleaner, but still has the issue of a hole when viewed from the top

is there no way to get the cross over without the hole, while also being clean?

I’ve somewhat achieved what i want by using crease and stitch after offsetting

Visually this is more or less what I want, but in terms of topology, that’s a 7 edge star, which from what I was taught, is generally not good?

SubD-CrossoverStitched.3dm (121.9 KB)

[Tom_P]

???

my initial post should just hint to a better topology.
I updated the file to have a nicer topview.

alternative - try to use _crease at this pointy start of the cut