topic Mesh Strange Behavior in Modeling

Mesh Strange Behavior

Anonymous — Thu, 25 May 2023 14:51:27 GMT

I've recently found a strange behavior on arc edges created with the Mesh Tool on AC24.
Is it the new standard (as I can see that now we can add a node on an arc edge without converting it to a straight segment)?
Note that the distortion of the arc goes below the base line and at the top of the slope it goes higher than the top edge.

Re: Mesh Strange Behavior

Minh Nguyen — Mon, 14 Sep 2020 09:19:47 GMT

Hello,

Thank you very much for your report!

The arc of the mesh looks strange indeed, but it was not clear to me what your question is about. I tested the same shape using AC22, 23 and 24, and all of them behave the same. Could you add a bit more information about what I should look for?

Thank you very much for your help!

Best regards,
Minh

Re: Mesh Strange Behavior

Anonymous — Mon, 14 Sep 2020 10:16:27 GMT

mnguyen wrote:
... Could you add a bit more information about what I should look for?

Hi Minh,
I recall previous Archicad versions to manage the Mech arc edge as an arc that links directly in height 2 points with different heights. So all the points in the arc are higher than the lowest node and lower than the highest node. And that is not happening here.
Some points are lower than the lowest node and others are higher than the highest.

Re: Mesh Strange Behavior

Minh Nguyen — Mon, 14 Sep 2020 10:54:27 GMT

Hi Braza,

Thanks for the information! So it is correct what I understood that the mesh looks...weird!

The earliest Archicad versions I have in my machine right now is AC20. Unfortunately, the same "weird" contours happen here for this type of spiral shape. I'm not quite sure how it is generated, so let me ask for a developer thought in this situation. Once I have an explanation I will let you know!

Best regards,
Minh

Re: Mesh Strange Behavior

strangeday — Mon, 14 Sep 2020 11:13:14 GMT

Hello, also I have noticed this behaviour(not only 24), seems that the AC try to create an ellipse passing trough start and finish point of the mesh segment(not clear to me where is located the third point that individuate the plane on which it lies, anyway), this condition seems exist only on curved segment >= 180°

as work around I try to insert point , trying to avoid segment greater than 180° envelop in plan, and adjust manually the height

Re: Mesh Strange Behavior

Anonymous — Mon, 14 Sep 2020 17:55:07 GMT

Yes strangeday. I noticed that >=180 degrees limitation. Probably the solution will not be easy.
This must be caused by the fact that the arc is constructed in a single plan. Like this:

So, to change this behavior, the edge would not be an ellipse. It would be more like a sinoid.

Edit: Or perhaps automatically break the arc edge in two parts (without creating a hotspot/node)... though only if the angle would be higher than 180º. Geometrically, it would be 2 twisted ellipses. Like a false sinoid.

Re: Mesh Strange Behavior

strangeday — Mon, 14 Sep 2020 19:56:48 GMT

Hello Braza, agree with you, probably is not so easy, or is quite expensive from computational point of view, even if AC already make a subdivision(based on magic wand segmentation setting) to construct the basic triangle of the mesh top surface.

So honestly I can't find why the curved edge couldn't be divided in sub arc edges internally with the height of the nodes given by a linear progression calculated by the Z difference between start and end point/segmentation value(as appear to work on edged curve <=180°)....

anyway, these are at the same level of bar chat ...because there could be some several limitation in the way AC treat the curve that could be overpassed only when a deepest integration with NURBS spline/surface will be adopted

Re: Mesh Strange Behavior

Minh Nguyen — Mon, 21 Sep 2020 07:46:43 GMT

Hi all,

Our developer has confirmed that (similar to what you have found out), the curved edges of the mesh are planar. Please have a look at the screenshot below. Unfortunately, we'll have to split the mesh in half for such situation to keep the arc less than 180 degrees.

I hope this has answered your question. Please let me know if you have any further question!

Best regards,
Minh

Re: Mesh Strange Behavior

Anonymous — Mon, 21 Sep 2020 14:33:40 GMT

Thanks for the confirmation Minh.
Yes. Its still weird, but I can live with it.
Cheers,

Re: Mesh Strange Behavior

Steve Jepson — Wed, 23 Sep 2020 20:00:25 GMT

another bothersome thing about a Mesh is that when you use Solid Elements Operations on it, it will display as expected in a 3D view, but not Plan View. The workaround it to convert it to a morph, but in doing that you loose the ability to use the Gravity Tool. Which does not work on a morph.

The situation I frequently have this problem is with making concrete flatwork plans. I use roofs for most of it bit the transition slabs need to have the nodes adjusted for z. But if I want them cut for columns, foundation vent wells, etc.. I have to convert the mesh to a morph. But then the gravity tool does not function on a morph.

THERE NEEDS TO BE JUST ONE FULLY FUNCTIONAL OBJECT FOR MORPH, MESH, SHELL, SLAB, ROOF, and if it were up to me that would include WALLS too. Anything you want to do with any of them ought to be something you can do with all of them.