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Modeling and drafting in Archicad. (Example: How can I model a Roof soffit/fascia?)

Moderators: Karl Ottenstein, LaszloNagy, ejrolon, Barry Kelly, Gordana Radonic, nbalogh, mnguyen, gkmethy

#309332
How do you control the level of resolution or segmentation of curved objects? Some object types have GDL parameters to control this, such as the 'Cross-Section Resolution' parameter in the guardrail tool, but there does not appear to be a similar parameter in tools like the beam tool (version 22).

ie: If I create a complex profile with a 90 degree filleted corner, in a beam extrusion using this profile I get segmentation at 45 degrees...so a 90 degree arc is modeled as 2 flat segments. However, using the exact same profile in a guardrail I have the option to choose my level of resolution.

Is there a project wide parameter that controls this for elements that don't have built-in GDL control?

Jeff
#321287
Hey Jeff, great question.

I'm also suffering the same issue with complex profiles that include circles. Unfortunately I haven't got a solution yet, keen to follow the thread and see what others have to say.

Cheers,
Ryan.
#321294
Have you guys checked your magic wand settings?

I'm not sure about v22, but in v24, you'll find them under Design » Magic Wand Settings...

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#321456
Archicad uses a surface modeler, which means that curved surfaces are approximate by 3D polygonal planes, and 3D curves are approximate by 3D lines. This is why you see that those curved geometries in 3D and in Sections look like they are segmented.

After a bit of research, I believe that curves defined in the Profile Manager are approximated in a similar fashion. Archicad has a built-in value of how much the lines/planes approximating the curves/surfaces can deviate from those curves/surfaces.
If you go to the Design > "Magic Wand Settings" Dialog, you will find that the "Deviation From Curves" option offers similar functionality, for example when you use the Line tool with the Magic Wand to approximate a curve.
What I just found now is that you cannot enter a value smaller than 1.0 mm into the "Deviation From Curves" options' "Less than" field. So Archicad has this hard-coded limit that you cannot approximate curves with lines so they deviate less than 1.0 mm from those curves.
Having such a limit may make sense since you would not want to allow people to set the value to 0.1 mm or 0.01 mm and then curves would be approximated my hundreds of lines, 3D curved surfaces would be approximated by thousands or tens of thousands of planes, and the program would quickly reach its limits in terms of polygon count in 3D.

The reason this is important comes into play when you have very small curves. When you have a curve with a 250 mm radius, Archicad can easily approximate it using 36 line segments (the default).
But when you have a curve with a 100 mm radius, Archicad can approximate it only with 24 line segments because if it used more segments, the deviation of the line segments from the curve would be much less than 1.0 mm. So Archicad calculates the lowest number of segments using which the deviation from the curve is less than 1.0 mm and uses that (or the default 36, whichever of these two values is smaller).
As you go smaller, Archicad can use a decreasing number of segments and still meet the above limitation. For example, if you have a curve with a 20 mm radius, Archicad can use only 12 line segments, if you have a curve with a 10 mm radius, Archicad can use only 8 line segments. I think 8 segments is the minimum Archicad will use to approximate a full circle. This is why you see that the smaller curved geometries are the more segmented they look because they bump into this limitation of the program.
It may worth noting that Archicad was meant to be an architectural program so its accuracies are set based on that. For example, in settings, you can set 0.1 mm as the highest accuracy in Working Units.

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#321659
Laszlo, is there any way to set the number of segments for a curve when using the column or beam tool with a complex profile? Or preferably the degree of rotation before creating a new segment, as opposed to an absolute length? I get some strange looking geometry when extruding a pipe where the inner circle of the profile is smaller than the outer circle and therefore has less segments...it would look better if the inner and outer curves of the pipe section had the same number of segments at least. Changing the magic wand settings doesn't seem to have any impact on the segmentation.
#321676
Not that I know of.
And I assume that those geometries are small enough (below 20 mm or so in radius) so the issues I talked about in my previous post come into effect.
#321680
Jeff Galbraith wrote: Thu Jan 28, 2021 2:10 am ...it would look better if the inner and outer curves of the pipe section had the same number of segments at least.
This was what Vistasp was suggesting by using the Magic Wand. You need to draw your circles (pipe in / out), then using the magic wand set to "Segments Along Circles" and a suitable value, you can then select the polyline tool and click on the circle to trace it using the Magic Wand. This will create a polygon to represent the circle. If you find the edges are too small to process then you can make the circles say 10x bigger, trace them and then reduce the polygon back to the required size. As far as I know the polylines should remain unchanged in the Complex Profile, although they will revert to separate line segments. Having got the polygons in the CP you can then create the required fill. I haven't used this for CP's but I do use it to improve curved profiles when using the shell tool.

This guide to Magic Wand Settings may help... https://helpcenter.graphisoft.com/user-guide/127974/
#321692
Is there no way to see and modify the segmentation setting of a segment of a polygon after it has been created? Or a way to over-ride the segmentation setting in the 3D geometry settings of the object extruded from the complex profile / polygon? I tried the magic wand tool and it doesn't seem to have any effect. I redrew the complex profile multiple times while changing that setting and it had no effect...and the default setting in the tool was 2"...which was clearly not effecting my geometry or the segmentation would have been much worse than it it. It would seem that there are other parameters effecting the output that are not captured int eh magic wand tool, or anything anyone else has suggested in this thread.
#321704
DGSketcher wrote: Thu Jan 28, 2021 2:57 pmThis was what Vistasp was suggesting by using the Magic Wand. You need to draw your circles (pipe in / out), then using the magic wand set to "Segments Along Circles" and a suitable value, you can then select the polyline tool and click on the circle to trace it using the Magic Wand. This will create a polygon to represent the circle. If you find the edges are too small to process then you can make the circles say 10x bigger, trace them and then reduce the polygon back to the required size.

Ah, so you are effectively handling the segmentation manually. How do you deal with the edge lines?



Ling.
#321726
Lingwisyer wrote: Fri Jan 29, 2021 2:38 am How do you deal with the edge lines?
Ok back to square one... I am sure there was a thread about CPs, resolution and hidden edges not too long ago but I can't find it just now.

On the roof I must have got lucky, perhaps as the radius was in metres rather than a few millimetres, but the Shell isn't showing any segmentation lines in 2D or 3D views, they only highlight when selecting the object. Perhaps the Shell has a smoothing element in its coding.

The attachment shows two 10mm radius bars / cylinders, the left is formed with a trace of 36 "segments along Circles" the other is a fill with 2 nodes and 2 arcs forming the circle.

So for the OP I there are the options of having:
1. Manually created segmented profile with edge lines.
2. A distorted polygon where the arcs are approximated by AC
3. Create the part with GDL if there is enough justification.

None of the above are great for the average user, particularly if the contractor follows the minimal segmentation in fabrication! :(
Attachments
CP segmentation
CP segmentation
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