Line length on circle scaled to ellipse is very wrong

baz

[attachment=0:1ln04vy0]conjuate ellipse.skp[/attachment:1ln04vy0]Baz: Do you know which type your equation is for.

Sorry Mac, I have no idea.

mac1

bAZ;
Complete integral of second kind required for ellipse;
For drawing Wikipedia best for you. The have an animated approach but call it parallelogram approach, mine almost the same but equal for all practical purposes. Will find link for you https://en.wikipedia.org/wiki/Ellipse
I used online calculator & my length is with .02+% of what they calculate.
I only use 4 points for may drawing then did mirroring to get 1/2. Most of curve was made with Bezier cubic spline Order 3 with seven segments. The scale and my drawing over lay very close.
I think know what problem is but need more test. Think may be adding segments ad infinitinum(sp?)my not be the way one wants to go. As you know SU has two sided faces so deleted duplicate vertices so could see what scale does and raised some questions I want to investigate.

mac1

160217.6 ellipse test.skp
@caul said:

@pilou said:

And what is its result in this case ? (Ellipse 400*900)

2118.2799288074484

The result above is for major = 900, minor = 400, if your input refers to the semi axes multiply the result by 2.

This is the correct value irrespective what Op thinks. On-line calculator spits out same number;
In addidition I used two different methods to model ellipse ( 10 x 20 ") to verify the model approach SU uses is ok ( Two circle and parallelogram, plus the one noted above but it is slight mod of parallelogram ) methods;
Attached the result I get for the 400x900 mm ellipse. The actual value is as above and I get 2112.236 => Good enough for me. I get same result if curve is exploded or left as curve. What I did seem to find is welding before scale helps and you have to be very careful to lock axis direction of scale.

pilou

Why not increase number of segments of arc circles for have a better precision?

@unknownuser said:

Sketchup gives 2118,27 6442 with circle 1000 segments!

baz

You guys really have to get out more

mac1

@pilou said:

Why not increase number of segments of arc circles for have a better precision?

@unknownuser said:

Sketchup gives 2118,27 6442 with circle 1000 segments!

Check my very first post you can make the figure with 75 segs very nicely. I do not subscribe to philosophy more is better. For the OP use one would probably want>=10% etc margin on veneer one buys.

pilou

you right but as we as a computer under the hands it's funny to give it maximum to eat!

Box

Can someone calculate the optimum sinewave formation for each of the individual nine tails used to flog this particular dead horse, please show all your working.