[V8i/SS10] Place quarter ellipse tangent to something?

I could swear I used to do this, but I could also be mistaken.

Is it possible to place a half or quarter ellipse tangent to two lines?

  • because I have problems getting "Move to Contact" to work the way I expect

    Yes, that tool is imperfect, and recently forced me to write a VBA program for the case between circle and ellipse with a given vector, it requires a complex calculation:

    en.m.wikipedia.org/.../Quartic_equation

    Therefore, that kind of process cannot easily be completed by basic drawing tool.

  • An issue which I recognise with what you have told us is that there simply isn’t enough information to place such an ellipse accurately .

    I work in drawings that may have an exaggerated vertical, like 1H:5V

    Is that a ratio or linear values for the Semi-Major and Semi-Minor axises (presumably in feet)?

    Additionally, can you confirm how the Major axis aligns in relation to either of the lines in your previous image? I think I am correct in the assertion that there are infinite combinations for the tangential points of contact between the lines and the partial ellipse so you need to reduce the Degrees of Flexibility by confirming what it should be e.g. should the major axis be perpendicular or parallel to one of the lines? This isn’t required with a fillet as its radius is constant, whereas you will appreciate that with your ellipse, it’s variable.

  • hi Mary , no mstn avail here anymore  being retired and Bentley Being extremally stingy about probono home licenses, but from memory under fillet we had circular right but wasnt there another option? I thought it was elliptical...  Geometry was  100 years ago at high school so whats special about a  quarter ellipse anyway 

    Lorys

    Started msnt work 1990 - Retired  Nov 2022 ( oh boy am I old )

    But was long time user V8iss10 (8.11.09.919) dabbler CE  update 16 (10.16.00.80) 

    MicroStation user since 1990 Melbourne Australia.
    click link to PM me 

  • But a quarter ellipse could be tangent to two lines with floating endpoints, as in, I know I need an ellipse tangent to two lines, but i may not know what the axis lengths need to be. This means that I don't know the exact points to click. It would also be possible for a quarter ellipse to be tangent to a line, just not at the quadrant.

    From time to time, i need to draw fillets with unequal scaling. I work in drawings that may have an exaggerated vertical, like 1H:5V. There are a few ways to place fillets like these, but I thought that placing a quarter ellipse might be a faster option:

    I had to draw this quarter ellipse off to the side and move it into place because I can't wrap my head around the calculations to figure out where either endpoint is. Even now, I'm not certain if the ellipse is actually tangent to the slanted line because I have problems getting "Move to Contact" to work the way I expect, but that's another discussion for another time.

    It's OK if this can't be done with the tools as they are. As I said, I have other ways of constructing what I need. 

    MaryB

    Power GeoPak 08.11.09.918
    Power InRoads 08.11.09.918
    OpenRoads Designer 2021 R2

        

  • The longer I think about it it seems there's something overlooked. A quarter ellipse needs two lines being rectangular to each other. Therefore there's no need for a second tangent.

    I guess you'll need to draw parallel lines to find the center of the ellipse and then go ahead.