topic Re: Splitting a mesh with an arc - Same question 10 years after ... in Documentation

Splitting a mesh with an arc - Same question 10 years after ...

Alskaro — Mon, 28 Jul 2025 09:53:18 GMT

Hello!

Everything is in the title .. I created a new post because I could not anwser to the old one (probably too old, what an irony).

How can I manage to achieve that ? Cutting someting with and arc or spline without to have a workaround with the magic hand tool.

On the previous post, some people said this method could not be used to cut slab or mesh because of the uncertainity of the intersection ..

Did someone at graphisoft found a solution after all this time ? I can magic wand an hatch with the curve I want and you pretend it's not possible to cut it ..

Maybe I missed something somewhere but I'm sure it's possible no ?

Well if someone have some idea about this topic ...

Thank you for your answer,

have a nice day!

Operating system used: Windows 3001 FRA FULL

Re: Splitting a mesh with an arc - Same question 10 years after ...

Barry Kelly — Tue, 29 Jul 2025 02:45:43 GMT

Splitting along a line is easy as it just chooses one side or the other.

Splitting linear elements along an arc is also easy as it just finds the intersection of the reference line and the arc and splits it there.

The end of the wall is not curved.

Splitting an non-linear shape along an arc is much more difficult.

It can't just cut everything to one side.

I am not sure a curved split would be an easy thing to program.

It might be possible, but it would be difficult.

Barry.

Re: Splitting a mesh with an arc - Same question 10 years after ...

Alskaro — Tue, 29 Jul 2025 04:37:30 GMT

Hello,

thank you for your message.

Sorry but I don't understand what you are talking about :

Could it not be done just with the same condition as for making the magic wand work ?(closed boundaries)

Have a nice day.

Re: Splitting a mesh with an arc - Same question 10 years after ...

Barry Kelly — Tue, 29 Jul 2025 07:41:31 GMT

Splitting on a line (or arc) it is just choosing one side or the other.

For an arc, I think you will find it is creating an infinite length line perpendicular to the radius where it meets the reference line of the element to be split.

So, for linear elements (lines, walls, beams) you are just dividing the reference line.

Forget my image in the first post (it should have said split, not cut).

Polygonal elements (slabs, meshes and fills) do not have reference lines to be split, which is probably why it does not work.

The split algorithm is looking for intersections of lines.

Take a simple 4 edge polyline on a slab.

How would it go about splitting this when the infinite edges all intersect each other.

That is why it will choose just the edge you click on to split.

Curves will be even worse, as there would be almost an infinite number of splitting lines to consider.

Thinking about it more, if the subtract polygon method works, why not adapt that algorithm to leave the subtracted polygon, rather than delete it.

Of course that would only work with a closed figure, not a spline or polyline.

Barry.