Hi Ali, Pilou shows how to get a circle inside.

To get an ellipse will be a bit trickier. Instead of drawing it with the ellipse tool, it will probably be easier to draw a circle and then deform the circle into the right sized ellipse using Transform / Scale / Scale 1D.

The Scale1D command stretches an object along one direction - when applied to a circle it will stretch the circle into an ellipse.

From the image, it looks like the effect you're looking for is taking a circle framed by a square like this:



And then deforming that square into a parallelogram:



Then you want the circle to deform into an ellipse in the same way that the frame was deformed.

To do this, you'll need the original square, the original circle inside the square, and the deformed parallelogram.

Select the circle and run Transform / Scale / Scale 1D. At the "Pick origin point" prompt, click the center of the circle:


At the "Pick scale direction" prompt, click the corner of the original square:


At the "Pick second reference point" prompt, click the corner of the deformed parallelogram:


Now you can delete the original square and you are left with the ellipse that fits within the parallelogram frame:


If you're starting with a parallelogram shape at some odd angle, you will have to do a few other steps to create the original square and circle. Let me know if you need the steps to do this part also.

Hope this helps!

- Michael

Yes a little bit tricker :) and surely more tricker if the quadrangle is anyformed (an ellipse by any 4 external points)
There is not function "Ellipse tangent" in the future?

Hi Pilou - any 4 points will make a curve that is made up of 4 different ellipse segments I think, not just one single ellipse.

Here is one trick you can use to deform a circle by 4 corner points, which is to create a trimmed surface and then move the surface points around.

Start by drawing a plane (not a rectangle, but a filled-in plane from Draw solid / Plane):



Now draw a circle centered on the plane:



Trim the plane by the circle, then select the resulting disk surface and turn on control points with Edit / Show pts:



Now the points can be adjusted and the circle trim curve on the surface will deform as the underlying surface is stretched around:



When you're done, you can extract the trim curves as a regular curve object by selecting it and using Edit / Copy then Edit / Paste.


> There is not function "Ellipse tangent" in the future?

Often times these kinds of calculations are more difficult with ellipses since there are more variables to define, like 2 different radius values instead of a single radius. This makes for a large number of different proportioned ellipses that can fit tangent to 2 curves.

- Michael

Thx for the tricky trick of the "trim plane(not rectangle) by circle" !
It always the more simple things that work better ! :)