Why do circles have cusp joins?

[jord]

If you create a circle it has cusp joins. Isn't it more logical to have smooth joins? When changing it to a smooth join the curve doesn't stay the same.
Also when creating other shapes, changing cusp joins into smooth joins the handles and therefore the curves change significantly.
Is there a way to create a perfect circle that has smooth joins?

[handrawn]

Is there a way to create a perfect circle

probably not in xara

you can construct one in a CAD program, but I don't think xara has that level of precision; still others may know better

however you do it, what you see is going to be affected by your monitor, in that most ordinary monitors have pixel symmetry that makes precice curve rendering very difficult if not impossible

[Acorn]

First off, make a perfect square. (F4 - Ctrl+Drag).
Next, enable Curved Corners and set to maximum by dragging the control to the middle or setting Curvature to 0.707 or grater.
At this point, in a web presentation, you have a SPAN with a shape that is as close to a circle as possible.
I am sure this will render as accurately to print.

Otherwise, take your cuspy circle or above and change to Editable Shapes.
Outside of the circle click=drag to select all four control points and press C.
All controls are no longer cusped.

In short, do not press S, use C.

Acorn

[gwpriester]

Fascinating, Acorn. I'm off to try this.

OK, I'm back.

Concert to Editable Shapes and press C, does not work for me in Designer Pro+. Nor does pressing the Cusp icon on the Infobar.

Creating a circle with no modifications, using the Radius Creation option and creating a circle from a square and making both the same size: 250px and then center aligning both and zooming in 300% does not show any noticeable difference.

[Acorn]

Fascinating, Acorn. I'm off to try this.

OK, I'm back.

Concert to Editable Shapes and press C, does not work for me in Designer Pro+. Nor does pressing the Cusp icon on the Infobar.

Creating a circle with no modifications, using the Radius Creation option and creating a circle from a square and making both the same size: 250px and then center aligning both and zooming in 300% does not show any noticeable difference.

Gary, the step between Convert to Editable Shapes (***) and press C is required.
***With F4, click and drag over the circle so all its controls are selected.

I always make a circle from a square as then in a web rendering it returns a SPAN, whereas a circle is presented as an image.

Acorn

[handrawn]

.....a shape that is as close to a circle as possible.
I am sure this will render as accurately to print.

good to know

just out of interest I zoomed into a circle I made this way at the 3oclock point to 25,000% zoom... seems it's gone a bit flat

[Acorn]

good to know

just out of interest I zoomed into a circle I made this way at the 3oclock point to 25,000% zoom... seems it's gone a bit flat

I just wound the control all the way up to 11 (25601%) and, yes, you might be right.
Although again, it could be my specs.

Acorn

[jord]

First off, make a perfect square. (F4 - Ctrl+Drag).
Next, enable Curved Corners and set to maximum by dragging the control to the middle or setting Curvature to 0.707 or grater.
At this point, in a web presentation, you have a SPAN with a shape that is as close to a circle as possible.
I am sure this will render as accurately to print.

Otherwise, take your cuspy circle or above and change to Editable Shapes.
Outside of the circle click=drag to select all four control points and press C.
All controls are no longer cusped.

In short, do not press S, use C.

Acorn

I tried that, I assume that after changing to edible shape I have to select the shape tool to select the nodes. When I press C nothing happens.

[gwpriester]

Jord - Same thing here. After I converted to Editable Shapes, I marquee-selected the four control points and pressed C and nothing changed. I also tried the Cusp icon on the infobar. I wonder if this has anything to do with using the Classic Keys setting in the Custom Key Shortcuts menu.

[Acorn]

I tried that, I assume that after changing to edible shape I have to select the shape tool to select the nodes. When I press C nothing happens.

Jord - Same thing here. After I converted to Editable Shapes, I marquee-selected the four control points and pressed C and nothing changed. I also tried the Cusp icon on the infobar. I wonder if this has anything to do with using the Classic Keys setting in the Custom Key Shortcuts menu.

OK, I have to rewind part of what I stated initially.
I always create my circles from a curved corner square.
When you convert that into Editable Shapes, instead of four control points, you get 8.
If you Tab into the shape and keep tabbing round, you see the control point alternate between Curve (C) and Line (L).
If you select all and press C, all are now Curve lines.

If you select+drag over a single control, you do not get the Cusp control points. The control acts as a Smooth control.
If you F4 and Tab repeated, you have the Cusp join on one of the two active Controls and Smooth join on the other.

There are all sorts of other things you can do by selecting more than one control.
Tab will catch one Control.
Select+drag over a control, snares two that are co-incident; Tabbing thereafter alternates adjacent and co-incident.
Select+drag over two adjacent Controls snares 3.
Select+drag over two opposite Controls snares 4 that can act as a pair or not.

I had always assumed a fully curved box was the same as a circle.

Acorn