Modifying PolyLines and Polygons

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# 2.2.8.7.1 Modifying PolyLines and Polygons

When a Polygon or a PolyLine is modified, open blue circle anchors show the position of its "nodes", these are selected with Left-Click and are shown as filled circles.

- Left-Drag of a selected node of a PolyLine or Polygon moves that node to a new position, and if moved close enough to a neighboring node will merge the two nodes and delete the edge between them.

- Delete or Backspace will remove a selected node.

- Left-Clicking on an edge will create a new node that can be dragged to position it.

- Multiple points can be selected using Shift+Left-Click. If these are then Left-Draged all the selected points move together, preserving relative position.

- There is a context menu that has controls for a selected point. It has options to alter the node into a rounded node (shortcut "r") or a smooth node (shortcut "s"). To turn it back into a sharp (vertex) node (shortcut "v").

- If Shift is held down while dragging, the relative angle for the first selected point to its predecessor point will be locked to a multiple of 90 degrees.

- When a node or nodes is/are selected, text entry boxes for length and relative angle (the deviation angle from the direction of preceeding side) can be used to fine-tune the position of the first node in the sequence. A arc indicator identifies the angle in question.

If no nodes are selected,

- A context menu can be used to close a polyline into a polygon (shortcut "g") or open it (shortcut "l") into a non-filled polygon between its last and first nodes.

- A unfilled polygon can also be filled (shortcut "f") or a filled one emptied (shortcut "u").

Notes

  A selected Polygon or Polyline node can only be deleted if there are at least three nodes left. It can only be round or smooth if long as it isn't an end node of a Polyline.

  Smoothed nodes implement a short Bezier curve that goes from halfway along the line of to the next node and which has a control arm that ends at the node. These are typically of most use to fine-tune a series of nodes that simulate a complex curve.

  Rounded nodes start at a distance that is half the shorter of the lines from the last node and to the next node and has control arms that extend to the half-way point to the node. This produces an arc whose radius is determined by the distance of the closet node. By manipulating the nearest node (for example, by adding a point) the radius at the node can be controlled.