No, not quite what I mean....



In the first case, where the arc angle is 90 degrees, they define the short and long axes of the ellipse of which we are using a quarter of it.

In the second case, which I crudely drew, you have center point ( 1 ), the first point of the arc ( 2 ) (the darker red dot ) and the third point ( 3 ) ( the one at the end of the grey line ).

Knowing (1), the center of the ellipse, the length from (1) to (3), and the angle of 1-2-3, it should be possible to determine the ellipse arc that passes through 1 & 3 and satisifies the angle 1-2-3.

Thus, in both cases, the center of the ellipse is in the proper position for both cases.

A better diagram of the second example:

So knowing the center 1, pt 2, and point 3, and angle 2-1-3 ( oops, typo in my prev post ), we can construct a arc of the ellipse that passes through 2 & 3.

In both cases, the center of the ellipse is always in the proper place!

I see - before I thought you were talking about doing something special for quarter-arcs.

I suppose this is possible - the command would have to be modified a bit because right now you don't actually have to pick 3 points, you can just do the first 2 and then enter an angle without picking a 3rd - this wouldn't be valid for the elliptical style.

I'll try to take a look at it tomorrow.

- Michael

Hi Crusoe - elliptical arcs will be in the next beta. Here is what it looks like:



There will be an "Elliptical" checkbox for Arc/Center. If you check it, the angle box is hidden and an elliptical arc is created as you described.

This does have some cool properties, since the elliptical arc will actually start and end on the points you pick, unlike a circular arc which uses the ending point as the angle which will only touch there if the point you pick is at the arc's radius.

It is also easy to do 90 degree elliptical arcs.

There are some slightly odd things as well, like you can't do a 180 degree elliptical arc because when the points are lined up in a straight line it doesn't have any way to calculate the length of the other ellipse axis. And it kind of oscillates in a bit of a strange manner as you trace the mouse around the center point. But that's ok.

I don't think it will be possible to make any of the other arc commands do ellipses, since there are not unique solutions to many of them. For instance you can't do an ellipse through 3 points because there are multiple possible ellipses that can fit through 3 points. But Arc/Center works because nailing down the center point and first ellipse axis length nails down the constraints enough.


Thanks for the feedback!

- Michael

Hi Pilou, re: extrusion direction

This is a limitation of the current extrusion command - it only knows how to extrude in one direction at a time.

Eventually I would like to enable multiple-object extrusion where each object extrudes by default along its own normal. But that was a bit more difficult (especially with the mouse interaction, there would be sort of multiple possible tracking lines), so when I was working on extrude I postponed that until some later version.

- Michael