topic Re: Drawing a circle inside a rectangle in isometric in AutoCAD Forum

Drawing a circle inside a rectangle in isometric

Anonymous — Mon, 06 Nov 2017 16:49:42 GMT

I'm getting so frustrated doing this. Basically i got an isometric figure and it has a rectagular slope. Inside that slope I need to draw a circle so that it would touch all four sides of the rectangle. But the problem is that it never touches all 4 sides. It always touches 2 of them and the other 2 sides are too long or too short. I've tried so many thing but it just doesnt work, nothing does... I've did the whole from scratch to see if maybe I drew it wrong but nope. Any ideas what could be wrong with it? Also the x thing is for finding the center.

Re: Drawing a circle inside a rectangle in isometric

john.vellek — Mon, 06 Nov 2017 17:09:24 GMT

Hi @Anonymous,

I see that you are visiting as a new member to the AutoCAD forum. Welcome to the Autodesk Community!

You are welcome to attach your drawing so I can take a look at the circle in isometric view. This is typically just done by creating an ellipse. Have you tried that yet?

Here is an older thread that discusses some options for creating this geometry.

Please select the Accept as Solution button if my post solves your issue or answers your question.

Re: Drawing a circle inside a rectangle in isometric

gotphish001 — Mon, 06 Nov 2017 17:24:46 GMT

As John said it would be an ellipse. You are looking at the circle from an angle so it will be warped slightly. Just like your rectangle isn't a rectangle. The angles shouldn't be 90 degree angles when looking at it in isometric.

It looks like even though it's a isometric drawing it is drawn in 2d. If you drew it in 3d you could rotate the drawing plane so the rectangle is a top view then it would be a circle you could draw on it.

Re: Drawing a circle inside a rectangle in isometric

john.vellek — Mon, 06 Nov 2017 17:31:05 GMT

HI @Anonymous,

Maybe the fastest way of creating this is to do it in 3D, switch to an Iso orientation and then flatten.

Re: Drawing a circle inside a rectangle in isometric

Anonymous — Mon, 06 Nov 2017 17:52:20 GMT

I am drawing an ellipse and isocircle both of them are not working. Either its over the rectangle or inside. But I need it to touch all 4 sides which doesn't seem that hard but it need too much work just to draw it. If draw 2 cirles then one of them touches 2 sides and the other one touches the other 2. I though that using trim of fillet would help but nope. I either have to draw it 3D or something else but atleast for me is way too hard. I haven't even started learning 3D yet. I'm sorry but I'm on edge right now cause of this circle is giving me headaches...

Re: Drawing a circle inside a rectangle in isometric

gotphish001 — Mon, 06 Nov 2017 18:12:06 GMT

Edited this. I told you the wrong way. Draw 4 arcs. Use the arc command "start,end, direction" Pick the start and end points of the arc as the midpoint of two adjacent sides then pick the direction point as the corner of the rectangle that is between those two side. Draw 4 arcs like this and it should look correct in your iso view.

Now I'm not sure if that will work. It seems to work on some sides of my test but others it doesn't not. It might be how I drew my test shape though.

Re: Drawing a circle inside a rectangle in isometric

Anonymous — Mon, 06 Nov 2017 18:16:57 GMT

Thanks! It looks almost like it should (it looks a bit like a lemons lol) but that will do. Though I tried doing it last time but it didnt work because of the direction. I had to go to the opposite side of where i started. First I went clockwise then the second arc counter-clockwise and so on. I had enough of this. Thank you!

Re: Drawing a circle inside a rectangle in isometric

gotphish001 — Mon, 06 Nov 2017 18:39:12 GMT

@Anonymous https://www.youtube.com/watch?v=Hg16J_4tmPk

Here is a great video on how to do it. I knew you could do it with 4 arcs but I was missing that you needed the extra 2 points to use as center points for 2 of the arcs. If you do it this way it won't look so lemon shape. I don't know what software the guy makes the video with but if you just do what he does with the corresponding autocad commands it will work out.

Re: Drawing a circle inside a rectangle in isometric

Kent1Cooper — Mon, 06 Nov 2017 20:00:20 GMT

Another way to approximate it, that may look a little better than the 4-Arcs approximation, is here. But that's not precisely accurate either [the Ellipse's "tangency" points on the rectangle's edges aren't at their midpoints]. This has come up before -- it turns out to be very difficult to arrive at the actual Ellipse to do it accurately on a plane that's not one of the isometric-axial ones, but if you Search the Forums, especially the Customization Forum, you should find some of those discussions.

Re: Drawing a circle inside a rectangle in isometric

john.vellek — Mon, 06 Nov 2017 20:37:29 GMT

Hi @Anonymous,

With all the wonderful posts in the thread I challenged myself to go through this exercise as I haven't actually done it in years.

I made a quick video for you that shows how I can use the ELLIPSE>ISOCIRCLE command to create the circle in isometric view.

Please select the Accept as Solution button if my post solves your issue or answers your question.