Rebuilding circle with little deviation ends up w. .5mm diff. in diameter

Rhino Rhino for Windows
1

Hello everyone,

i have the problem that I would like to blend two surfaces. One of them is a circle (100mm diameter).
When I BlendSrf them, the circle is automaticly rebuild and the diameter is off by sometimes 0.5mm.
I thougt I could work-around this problem, if I rebuild the circle before I BlendSrf them.

I tried rebuilding a 100mm diameter circle with 16 points and degree 3, resulting in 0.00320616 maximum deviation. But still: when i check the diameter with the diameter command at some areas the circle has a diameter of 100.503mm … how can I minimize this number?

Another example: 50mm circle > rebuild with 18points + deg. 3 (0.000996221 max deviation) > some areas have a diameter of 50.262mm or 49.722mm…

Thanks a lot.

2

Hi Niklas - please post the objects in a Rhino file.

Rebuilding circles is pretty good with degree 5 and 24 points. But it will always be an approximation.

-pascal

1 Like
3

Circle Rebuild.3dm (59.1 KB)

Thank you! The degree 5 and 24 points tip worked fine :smiley:

4

Hi Niklas - I am not clear on the original problem - what surfaces are you blending and what rebuilding takes place in that process?

-pascal

5

Here, take a look. I still have a 49.834mm diameter at the end on the Quad point after the BlendSrf
BlendSrf Problem with diameter.3dm (1.9 MB)
…

6

Hi Niklas the radius will vary more, locally, than the deviation from the true circle due to slight variations in curvature along the edge. The deviation from the true circle is ~.0001 or less and the overall size of the edge curve is
50.00000 by 50.00000 millimeters

-Pascal

7

How did you get the numbers? I would like to analyze this by myself in the future. Thanks!

8

Hi Niklas - CrvDeviation and BoundingBox commands.

-Pascal

1 Like
9

Thank you! Really helped :smiley: