How can I cut an opening using geometry segments as boundaries?


How can I cut an opening as I show in the picture, without creating problems with the geometry? The curve I am trying to create it’s a Bezier one…


It’s not clear what you’re trying to do or what problems you are encountering.



Thank you, I was trying to update the picture… Take a look at the new one!


Okay, I tried it and it seemed to work fine. I think you’re not using inferencing to make your arc perfectly tangent at the ends.

Keep working at it. Watch for magenta inferencing when you draw the arc.

Also, the number of segments on your curves seems rather excessive.



From the top image you can see that this is a “too small geometry” problem:

scale your model up before you draw the arc and it will work fine.


It’s not an arc, it’s a Bezier curve… I think that this is the problem. I am drawing it with a plugin (BZ Toolbar).


I think not (see my reply).


Why not use the Arc tool? What you’ve got doesn’t call for a bezier curve. You’ve clearly got bad tangencies.



… only because the geometry is to small.


Obviously @Cotty, we don’t agree on this one. It looks to me as though there is an issue with the geometry’s form, not its size.

One would have to see the model to be sure. But I look for missing faces as a symptom of undersized geometry, and I see none. What I do see is some sort of moire pattern–an interference pattern.

But by all means feel free to restate your theory as often as you wish.



Ack! This time the lack of an uploaded model has gotten the experts arguing! Why is it posters persist in thinking an image adequately nails down their problem?

PS: in this case if you look very closely at the OP’s pictures you will see that the hidden lines leading to the arc are not parallel to the next ones over on either surface. This makes me suspicious that these lines were “captured” by passing too close to the arc at a very small size. If the arc were drawn sloppily I wouldn’t expect it to pull these edges askew. Alas, @Gully_Foyle Gully, that would support @Cotty’s argument.


As explained by @slbaumgartner, this problem with the geometry is because of its size…

I’ve marked these lines in my first answer.

Edit @formlesscloud: it doesn’t matter which tool you used to create that small geometry (arc, bezier plugin, …)


As shown in the video, this is another instance of SketchUp’s Vertex tolerance in action. The Edge passes within the tolerance of one of the Vertices of the arc, so SketchUp detects an intersection and diverts the Edge over to the arc.

But to reiterate, without a model we are speculating based on visual evidence.


I hereby ingest a slice of humble pie: you gentlemen are correct. Here is my original model scaled down x.01. The truth of your theory is now manifest.



Thank you, so the answer is that I must chance the dimensions of my model if want to create that curve? What if I want to keep the dimensions of my model as they are rigth now?


You scale it up while drawing the geometry, then scale it back down afterward. The problems with small size occur while creating the geometry.