Produce a curve by intersecting two surfaces?

[in1291]

I was wondering if its currently possible to achieve the following: Generate a curve as a result of the intersection of two surfaces?
In the following example, the yellow line shows what would be this resulting curve:

[portnov]

No, unfortunately there is currently no clear way to do this, at least in core Sverchok.
You can try to find some workaround which would work in your particular situation.

If you have FreeCAD libraries installed, AND your curves are NURBS, it's probably possible to write a scripted node which would calculate your curve.

[rendetto]

@in1291 you can try with Solid Boolean and then extract the specific edge. You just have to manually search for it.

[rendetto]

Yep! That's the solution:

[rendetto]

@portnov is it ok if I try adding the option in the node? :)

[portnov]

@rendetto you mean to "Solid boolean"? not sure. Probably this deserves a separate node.
Because if you do solid1.section(solid2), where solid1 is, for example, a cube, and solid2 is, for example, a sphere, you will probably get something strange, I guess (?). So probably it should be a separate node, which accepts surfaces (SvSolidFaceSurface's, to be exact), not any Solids.

[rendetto]

"Solid Boolean" fortunately accepts surfaces(and also curves), I was using this obscure feature before but never was aware how universal it is.
What I was planning to do is very simple (just adding the option "Section") and looks like that:

Intersection curves look pretty ok between Cube and a Sphere:

It works for intersecting curves:

And between surfaces and multiple curves:

...Surface can intersect a solid cube without problems as well:

[portnov]

Hmm, very nice.
But the output always contains only edges? Then probably output socket should be of Curve type, not Solid in this mode.

I'm just a bit confused about adding this mode in Solid Boolean. When we say Boolean, we usually mean Intersect / Union / Difference, not something else. If someone will search for this operation, they will probably not be expecting to find it among boolean operations. So maybe separate node will look better, even if it will be partly a copy-paste of Solid Boolean.

[nortikin]

solid-soid = solid # solid boolean
surface-surface = curve # solidbooleat
curve-curve = point # curve booleat

[portnov]

Implication 2

Well, if we can't implement "accumulate nested" correctly, let's just not support it for this operation.

Implication 3

Maybe it will be better to have two outputs, "Curves" and "Vertices"? Or Shape output object provides more possibilities than just decomposing it to edges and vertices?

[rendetto]

Thanks @portnov! Is it ok like that?

[portnov]

Yeah, looks good!

[rendetto]

I managed to test and stabilize the node finally. What left is the documentation (which is almost done) but I'm a bit confused. Where or how should I upload the images I want to show in the docs?

[portnov]

Usually we just upload them to github (for example into description of PR, or into comments) and give links to them.

[rendetto]

I finished the node https://nortikin.github.io/sverchok/docs/nodes/solid/solid_section.html

There is something to consider though. We have to be aware that the resulting curves are of degree 1 - high resolution polylines.

So if smoother results are needed the intersection curves could be approximated with the existing methods.

Cheers