I want to adjust opposite nodes on a path, made from a shape tool, simultaneously to maintain symmetry. For example I make an ellipse, convert the ellipse to a path, then select the two nodes opposite each other and make them symmetric nodes then lengthen one handle by 50% or so, I want the other selected node to do the same. Is there a way to do this?
Not simultaneously, but it's simple to do it manually by using guides, the snapping option: Snap Nodes Paths and Handles, and by holding down CTRL as you click and drag the Bézier handles to constrain the angle.
There is also a rather convoluted way to make symmetrical shapes automatically. It's probably too complex for your particular scenario, but certainly useful for more complex symmetry.
You can create a half ellipse, clone it, reflect it, move into position. Then the edits made to the clone source will update automatically in the reflected clone.
My technique is to draw only half of the shape, and use a clone for the other half. This way you can edit the original half and the clone will update accordingly:
- First create your ellipse and convert to path.
- Check your snapping options so you can easily overlap a rectangle over the left half.
- Select both objects and Path -> Difference.
- Edit the path to remove any unwanted segments.
- Clone your half shape (Alt-D), and flip the clone horizontally (H).
- Move the clone so it snaps in place.
- Now you can edit your original path and the clone should follow.
If, when finished, you want to convert the whole thing into a single path, you can select the clone, then Edit -> Clone -> Unlink, then combine the two paths into one, and optionally check for resulting double nodes with the path tool.
Another technique is to use a path effect called mirror symmetry, which gives more flexibility but is trickier to use.