Inkscape: The Penrose Triangle / Circle

Question

I just started using Inkscape and know how to make triangles and circles and learned about layers where you can put one object over another. But I want to 'interleave' the circle/triangle objects as shown here,

I figure it can be done by breaking up the objects and using two layers, but I want it to retain the 'perfect' symmetry.

So how to design this interleaving of an equilateral triangle with a circle?

Besides solving this with an Inkscape file, it would be very helpful to include an outline of the steps used to get the result (so I can try to also design it from scratch).

Answer 1

Here's one possible method. No extra layers are required.

1. Select all Ctrl+A. Do Path > Stroke to Path. This will convert the strokes to filled paths.

2. In the Snap Controls Bar, enable Snapping, Snapping to Nodes (Global), and Snapping to paths.

3. Using the Bézier tool B (aka Pen tool), draw three covering patches like this. The Pen tool will snap to the paths.

4. Then set the fill of these pieces to the same colour as the triangle.

Answer 2

You need only one layer, but you must split one of the objects after placing it and adjust the foreground-background order.

You can put point snaps ON and allow snapping to the object midpoint or rotation center which are by default the same in this case. Simply move the circle or the triangle until it snaps. As said: do this before splitting anything.

In the next image there's shown the final result. In the right those pieces of the splitted circle which are sent to back are colored to green.

To split the circle:

Apply Path > Object to path. Then double click to the wanted splitting points with the Node tool.

Lock the triangle in the objects panel.

Select splitting points and apply "break path in the selected node" - it's in the Node tool options bar.

Apply to the circle Path > Break Apart to make the splinters free to be sent to back.

As you see, the stroke end style is rounded. It makes the stroke ends to overlap and prevents the 1 px wide half-transparent anti-aliasing zone which occurs in Inkscape and in many other graphic programs and makes perfectly fitting seams look like there's a gap.