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.
Lingwisyer wrote: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.
How do you deal with the edge lines?
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!
