Circle outline with radius control?

Hi All, just installed Synfig and having a play with it, but something I though should be really simple seems to be very hard to do, can someone tell me where I’m going wrong?

I want to create a very simple animation, with an expanding circle (outline only, as there is other stuff behind it that needs to be seen).

When I create a circle outline, the only way I can get it to be visible is using the “Create Outline Bline” option, but that does not provide me with a circle with radius control, but rather a series of b-lines with each point having separate controls… not very helpful for just changing the radius of the circle.

I had expected to do this:

  1. Draw circle with solid outline, invisible fill.
  2. Create keyframes
  3. Change radius of circle as required on each keyframe.

… but I simply can’t find any quick and easy way to do that! could someone let me know what the easiest way to crate an expanding outline circle animation is (I don’t want the thickness of the line to scale… only the radius).

Another annoyance… why can I not delete an object by pressing the delete key on my keyboard… isn’t that the most standard and recognized way to delete an object in just about every program? I am curious why the developers chose the Right-click menu only option, wouldn’t this be rather annoying to most new users?

Apart from that, the program is great, congratulations to everyone working on it… it’s nice to see an FOSS animation package that really looks like it’s going in the right direction, and even in this early stage it is very usable.

Fedora 12 Linux (2.6.32)
KDE 4.4.2
Synfig Studio 0.62.00 (from fedora repository)

The easiest way is to use the Scale Tool. Scale tool usage is simple:

  1. Drag a box around the ducks you want to scale.
  2. Once the ducks are selected (highlighted) click and drag one of them and the selected duck will scale around its geometrical center (which in this case it is the origin of the circle). As the width ducks are not visible, they are not scaled.

Alternatively to this you can create a ring based on two concentric circles.

  1. Create two circles of different radius at different origins.
  2. CTRL click each circle origin and then r-click one of them and select “Link” from the contextual menu. The origins will be linked and the circles will be concentric.
  3. Place the inner circle layer above the outer circle. Change its blend method to “Alpha Over”. It will create a hole in the lower circle.
  4. Right click on the internal circle radius duck and select “Export”. Give it a meaning name.
  5. Go to Child’s Panel and select the already exported radius Value Node.
  6. Select the outer circle in the layer stack and go to Param Panel. Search the Radius parameter. Right click it and select Convert->Add. It will turn outer radius to a sum of two sub parameters.
  7. Once converted expand the radius parameter to see the sub parameters. Select the first sub parameter and right click ->“Connect”. It will connect the subparameter to the inner circle Value Node you already have exported and selected in the Child Panel.
  8. Edit the second sub parameter and give it a proper value to represent the thikness of the circle. Remember that radius is in Synfig Units and that 1 Synfig Unit = 60 pixels by default.
    After that you can click and drag the inner radius and the outer radius will follow.

The DEL shortcut was modified to CTRL-DEL since 0.61.09 version. Previously pressint DEL when editing the name of a layer caused to delete the layer, what was more confusing even for any user.

Thanks heaps! we are preparing a new minor release 0.62.01 and it will be out in a few days.

Or the other approach would be to use two circles with the same origin, and have the upper one be slightly smaller one with an ‘alpha over’ blend method.
You’d have to animate the radius of both circles to maintain a constant width, but it may be easier than juggling the 4 bline points.