Drawing an Ellipse

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Rick
Junior Member
Posts: 11
Joined: Sun Oct 04, 2020 9:07 pm

Drawing an Ellipse

Post by Rick » Thu Jan 01, 2026 11:00 pm

I am trying to make an isometric drawing of an circle.
When I try do draw an ellipse it asks for x and y radii and the angle.
I know the radius of the original circle and the angle, 30 degrees.
How do I calculate the x and y radii?

Thanks for the help, Rick

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Husky
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Posts: 5071
Joined: Wed May 11, 2011 9:25 am
Location: USA

Re: Drawing an Ellipse

Post by Husky » Thu Jan 01, 2026 11:24 pm

Rick wrote:
Thu Jan 01, 2026 11:00 pm
I am trying to make an isometric drawing of an circle.
Hi,
may I ask you why you are not using the QCAD Isometric Projection tools below Menu: View > Top Projection etc ? To easy? :wink:
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If a thread is considered as "solved" pls. change the title of the 1. post to "[solved] Title..."

CVH
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Joined: Wed Sep 27, 2017 4:17 pm

Re: Drawing an Ellipse

Post by CVH » Fri Jan 02, 2026 4:24 am

Hi,

An isometric projection of a Circle, an Arc, is a bit more complex than a scaling factor.
It is an inscribed Ellipse in a quadrilateral or a part of such a full Ellipse.

For hand-drawing, project the axis-aligned square to isometric and draw an inscribed Ellipse (EQ) shape in that .
Crop that for an Arc at projected endpoints.

The angled cut of a circular object is also an Ellipse contour in the cutting plane.
Then it is the simple matter of scaling one of the radii.

Regards,
CVH

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