another yucky geometry question

Jim Hurley jhurley at infostations.com
Tue Sep 27 12:42:56 EDT 2005


>
>Message: 3
>Date: Mon, 26 Sep 2005 18:53:36 -0700
>From: TJ Frame <tjframe at gmail.com>
>Subject: Re: another yucky geometry question
>To: How to use Revolution <use-revolution at lists.runrev.com>
>Message-ID: <7348a9e8050926185375614ce4 at mail.gmail.com>
>Content-Type: text/plain; charset=ISO-8859-1
>
>Thanks so much Jim, but alas, as this screenshot shows neither axis will
>ever be parallel since this is a 2D perspectiev drawing utility. This second
>image of the link is a screenshot shows a typical VP setup that might exist
>and all the variations of ellipses that might result...
>  http://www.tjframe.com/EllipseExample.htm
>  But as I alluded to earlier, Perhaps this would be beyond the scope of
>something I could implement. I know that 3D do ellipses every day, all day
>long, so I had assumed it would be a straightfoward task. But I guess they
>use matrix calculations to generate the points of the object rotated and
>stuff. Perhaps I would need to have a 3D underpinning for the ellipse stuff
>to work..
>  For now I'll put that feature on hold.
>  Thanks again guys,
>  - TJ

TJ,

Using the drawEllipse handler it is not hard to draw an ellipse of 
any dimension, at any angle, at any location. It is fairly  quick, 
about 8 or 9 millisec. But, as I said, there would be a fair bit of 
calculation required to GET the proper loc, dimensions, and angle. 
You would need to expand on the calculation I used in the stack 
"ellipseInAbox" to make the ellipse tangent to the radial lines. A 
bit of work, but doable.

Jim




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