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Design forum

Semicircular Mesh

Anonymous
Not applicable
Hello,
I have run into something strange with the mesh tool.
The attached image shows a semicircle drawn with arcs and lines.
Above that is a mesh made by tracing the figure made with arcs and lines.
When I go to the 3D window to view the mesh I get a warning
saying "Invalid polygon, self-intersection or hole intersects boundary".
Nothing appears in the 3D window.
If I trace the same figure using the slab tool or the roof tool and
go to the 3D window I get no warning and the slab or roof
show in 3D.
If I make an object out of the mesh using save selection as GDL Object
and open the objects 3D script and check script I get an OK but
if I go to the 3D view I get an error message saying
"Invalid curve definition at line......" and the 3D image fails to process.
I have tried this in both AC 8.1 and AC 9.
Would someone verify this behavior and perhaps
suggest a way to make such a mesh shape work.
I know that if I make the included angle one degree less than 180°
or make the inner radius 1/64" less than 10'-0" the error does not occur.
This work around is not satisfactory.
Thank you,
Peter Devlin
25 REPLIES 25

Anonymous
Not applicable
Hello Peter,

I'm not sure what could be causing this, I just created the mesh in the same way that you described, but I can't reproduce the error. Maybe it has to do with the magic wand tool, I have run into the same error when creating meshes with the magic wand tool... How exactly are you using it to create the mesh?

cheers,
dan

Anonymous
Not applicable
Daniel wrote:
Hello Peter,
... I have run into the same error when creating meshes with the magic wand tool...?
Hi all,

Daniel I have created semi- how Peter has described with magic wand tool and no error! How you poeple use wagic wand tool? I have done test on 3 main places of semi- using MWT:
1. inside (in different places)
2. along perimeter on different points
3. on corners
and no error!

So guys "How exactly are you using it?"

Anonymous
Not applicable
Hello Dan,
I did not use the magic wand tool.
I used pet palette tools exclusively.
You cannot reproduce this error?
I have drawn this shape maybe six or seven times and always
get the error when the dimensions are as I described.
I draw the arcs and lines as shown, then draw a four cornered
polygon with the mesh tool with one of it's edges laying across
and spanning the diameter of the larger arc and the remainder
of the mesh lies below this line.
Using the arc pet palette method I stretch this edge up to the
outer arc, then I drag the two remaining nodes to the left and right
ends of the inner arc, respectively.
Now I have half circle shape with four nodes laying in a line at the
diameter. Then, using the arc pet palette method I stretch
the edge between the two inner diameter nodes up to the inner arc.
I hope this is clear.
Thank you,
Peter Devlin

Anonymous
Not applicable
I actually drew two circles, one 1000mm dia, one 700mm dia, then I drew a line through the center point, and trimmed the line, and two cricles to the shape you are using, then I selected the mesh tool and click on the outside arc, and it worked fine...the only time I've ever gotten the error was when I imported a line drawing from AutoCAD and used the magic wand tool to create mesh points for a topographic site plan, and looking back on it, it was caused by intersecting mesh lines at different elevations.

hope this information helps

cheers,
Dan

EDIT: PS: What font is that that you're using Peter... off topic for sure, but I really like it

Anonymous
Not applicable
Hello Dan,
The font is called "MrHand".
I don't know if it is available for Windows.
It may be only for the Mac.
Thanks,
Peter Devlin

Anonymous
Not applicable
This is getting stranger by the minute.
I tried the magic wand tool on the arcs and lines
and it made a mesh that had the same error.
I then dragged a copy of both the flawed mesh I had
drawn and also the flawed mesh that was made
with the magic wand tool and both copies displayed
in 3D with no errors.
I don't understand.
Peter Devlin

Anonymous
Not applicable
riiiight... I'm not sue if thats another puzzle piece or if the ArchiCAD gods just snatched a piece out of your hand... I honestly have no idea what could be causing that.

cheers
dan

Anonymous
Not applicable
I got error(with MWT too),
formerly I have drawn with custom dims.

I don't know what's the problem is, but after short test have discovered that you/we have problem with inner Radius(not yet outer). And the problematic radius is in RANGE [9'-10" ; 10'-1"] (or in meters: RANGE [3.0000 ; 3.0700]).

Anonymous
Not applicable
Hello Z.Bauer,
In my test of the magic wand tool I just clicked
inside of the closed shape I had drawn with arcs and lines.
I was surprised to see that it made a tracing with two arcs
and two straight edges and four nodes rather than a polygon
with many nodes and straight segments.
I will have to check the magic wand settings.
Thanks,
Peter Devlin

Anonymous
Not applicable
Hello Z.Bauer,
I am gratified to hear that you have verified the problem.
I have drawn two meshes that are identical to the one
that is flawed except that the inner arc is drawn with the
three point arc method in such a way that at the top midpoint
of the arc is 1/64" less and 1/64" more than at the
start and end points of the inner arc which are exactly 10'-0".
I believe this makes arcs that are not exact semicircles.
These two meshes do not generate an error.
Thanks,
Peter Devlin

Anonymous
Not applicable
TEST RESULTS:

I have created 4 point mesh with dims there are represented on the image. As already have sad error runs in 3d. I have saved mesh as Mass.gsm GDL Object to check the coords.
Have found nothing that can bring any conflict.
I think this bug in MASS function for specific dims, because than I have added Mass coords in to POLY_ , EXTRUDE , SLAB function to check and generate script in 3d. And they work fine!

Tested objects are attached!

Anyone can prove that that's not a "bug again from GS"

Anonymous
Not applicable
Yes Peter,
I have added 3rd point in the middle of inner arc too and it's work's fine without any problem. And actually the problem must not be. I remember that something else was when I worked on AC 6.5(7). Most of curved meshes and slabs in my projects I had done with min 3 points on a curve due problem like this one.

Anonymous
Not applicable
Hello Z.Bauer,
I am a bit confused by your last post.
You say:
"And actually the problem must not be"

Are you saying you have concluded
there is no problem with the mesh tool in this context ?
Thank you,
Peter Devlin

Anonymous
Not applicable
Hello Z.Bauer,
I opened your library part with the MASS command and viewed in 3D
and get the same error as I got when I did the same thing.
I also could not see anything in the script that would cause the problem.
Thank you,
Peter Devlin

Anonymous
Not applicable
Doing a little experimenting, it seems that if an exact semicircle
is drawn on an edge of a mesh, either concave or convex,
the mesh fails to generate in 3D and an invalid polygon error is reported.
It seems clear to me that the unique properties of an exact semicircle
is causing the problem, but only for the mesh tool and only if the semicircle
is drawn on the edge, semicircular holes don't cause a problem.
Other tools are not affected.
So, hopefully, GS will have something to say about this issue.
Thank you,
Peter Devlin

Anonymous
Not applicable
This has truly been one of the most interesting issues / bugs I've ever seen in ArchiCAD.. congrats Peter

cheers,
dan

Anonymous
Not applicable
Peter wrote:
Hello Z.Bauer,
I am a bit confused by your last post.
You say:
"And actually the problem must not be"

Are you saying you have concluded
there is no problem with the mesh tool in this context ?
Hello Peter again,

no, as I have sad and shown in attached files the problem exist, but just looking generated coords I sad "actually I see no problem, this is "crafty bug""!

But I wasn't attentive:
AC has generated not correct coords for Mass. I have done some additional tests to find the problem. And here is that:

!METHOD TO FIND THE PROBLEM:
!1. The autogenerated for MASS object coords was added in to SLAB function.
!2. 2D and 3D HOTSPOTS with the same coords was added.
!3. After generating 3D for SLAB and zooming left corner/point on the inner curve,
! One additional problematic point was found (see on attached image & in file)

I would say is bug and GS must solve problem.

Anonymous
Not applicable
Problematic Point:

Anonymous
Not applicable
Hello Z.Bauer,
"crafty bug"" indeed !
I found the same thing with a slab with a concave quarter arc cut into it.
In my case the extra point formed a protrusion at one corner.
Peter Devlin

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