Points and Edges

Creating Points and Edges

Create Points

pointedge     Using the Point-Edge Tool

  • Click a location, then click it again.

        Using the Keyboard

  • Press spacebar and enter coordinates for the desired point. FISH symbol(s) may also be used.

Merging Points

Select and drag one point onto another to merge the points. Holding down the Shift key while dragging a point will prevent merging.

Create Edges

pointedge     Using the Point-Edge Tool

Any of the following methods will produce a new edge(s).

  • Click a location, move the mouse to the intended endpoint, click.*
  • Click an existing point, move to another existing point, click.
  • Click on an existing edge to split the edge in two at that point.

Constraining — When using the Point-Edge tool, pressing Ctrl constrains the angle of the edge to 15º increments. The default value is 15º but can be changed in the “Sketch” panel of the Options dialog.

Suspend Snapping — Pressing Shift while using the tool will prevent object snapping (this keeps the mouse from snapping to/onto objects that it approaches).

*The Point-Edge tool operates in “segment” mode (as described above) by default. In this mode, the next segment is created using the same click-move-click operation, but the first click is performed on the point that ended the previous segment. The tool has a polyline mode as well that allows creating multiple edges in one mouse pass. Switching the tool to this mode is done using the “Polyline” setting in the “Sketch” panel of the Options dialog.

Create Curved Edges

addcontrolpoints     Using the Control Point Tool

  • Click a location on an edge to add a control point at that location, and move the point to the desired location by:

    • Keeping the left mouse button pressed when placing it and dragging it to the desired location.
    • Releasing the left mouse button at placement, then click-and-dragging on the point (right- or left-mouse button will work for this) to the desired location.

At this point, the control point will serve to curve the edge. However, all edges are created as “line”-type edges by default (the default may be changed in the “Sketch” panel of the Options dialog). To obtain a curve, the edge type property of the edge must be changed to the “curve” type (e.g., right-clicking the selected edge and chose Edit Edge Properties).

../../../../../../../_images/makeCurve.gif

Figure 1: Once an edge has one or more control points on it, obtaining a curved shape from the edge requires changing its edge type property to “curve”.

Deleting Points and Edges

Points

Select one or more points and press the Delete key. Note the edges connected to the points are deleted as well.

Edges

Select one or more edges and press the Delete key. Note the points at the ends of the deleted edges are not deleted.

Tips

Avoid Intersecting Edges When Building a Structured Mesh

Zoning a structured mesh requires that edges be formed into three- or four-sided blocks. As a result, do not draw the point-edge tool for one edge across another (see the image below). Where edges meet, a point must mark the location where they do.

../../../../../../../_images/intersecting_edges.png

Figure 2: Illustration of valid and invalid techniques for drawing edges for structured mesh blocks

Using the Right Mouse Button

Bear in mind that when the point-edge tool (pointedge) or the control point tool (addcontrolpoints) is active, the regular selection functions of the select tool (selecttool) are available from those tools’ right mouse button, as described in Right-Click Selection Overload.

Edge Zoning

Main Zoning Properties

The edge properties “Zone Size”, “Zone Length”, and “Ratio” will all affect the zoning produced from an edge. These are set/changed using normal object property editing methods.

Zone Size

This setting determines the number of zones to be created along the edge. Zones are demarcated with red “x” marks along the edge. Setting this property will override an existing zone length assignment.

Zone Length

This setting specifies an exact length for zones along the edge. When used, the edge will be split into an integer-expressed number of zones that are closest in size to the value provided. Setting this value will override an existing zone size property.

Ratio

Specify a distribution of zone sizes along the edge using a ratio. A ratio of 1.1 means that each zone succeeding zone size in the direction of application will be 1.1 times the length of the previous zone. If not specified, the default ratio is 1.0. Use the “Reverse” button adjacent to the value field to set the ratio in the opposing direction.

Changing the Zoning Defaults

Any newly created edge is given default zoning of four zones per edge. This is the default setting on program installation, and may be changed using The Edge Parameters dialog (image below). The dialog is accessible through the pulldown menu (pdtriangle) on the point-edge (pointedge) tool button.

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Number of Zones per Edge

Select this option to input a new default number of zones (within 1 - 10000) for new edges. Changing this value will not affect existing edges.

Length of Each Zone (appr.)

Select this option to input the length of each zone (within 1.0e-5 - 1.0e5) for new edges. This value will be approximate to allow fitting a whole number of zones per edge. The initial default value when starting the application is 10. Changing this value will not affect existing edges.

If the specified zone length causes the number of zones on an edge to exceed the limits (1 - 10000), the limit value is used for the edge.

See Also

In addition to setting zoning along edges, as described above, zoning within a block may be affected the block property zone multiplier, or by the operation of the automatic zoning tool. Refer to the topics below for more information.

Advanced Edge Operations

Creating Edges from Background Geometry

A geometric data file (e.g. DXF, GEOM, STL files) imported into a sketch set contains numeric information decribing the geometry. This information can be used to create that conform to the background geometry. This can be done manually as described in Background Images / Geometric Data or automatically by pressing the Automatically Create Edges button (autoedge). When using the latter option, edges are created for every edge found in the background geometry.

Automatic edge creation is only available when a background geometry is present.

When creating edges from background geometry, the maximum number of zones which will be set for an edge is 1000 even if default edge parameters are set to more than 1000 zones. This is done for faster data processing and to avoid unnecessary memory consumption. If the number of zones on any automatically created edge is reduced to 1000, a warning message will be shown. Number of zones can later be changed individually for each edge in the Object Properties dialog or for all edges by using Automatic Zoning.

Note that a curved edge in the background geometry is represented by a number of straight segments and sketch set edges are created along them. These edges can later be combined into a single curved edge as outlined below.

Selecting Edges by Break Angle

In order to select a number of connected edges at once press Select Edges by Break Angle button (selbybreakangle) and click on an edge. All edges connected to it will be selected as long as the angle between two neighboring edges is below specified break angle. The selection also stops if an edge is connected to more than one other edge on any of the sides.

Edge selection mode stays active until user presses Select Edges by Break Angle button (selbybreakangle) again to deactivate it.

The break angle can be specified by placing mouse cursor over the numeric value and scrolling mouse wheel or pressing up or down buttons.

Combining Edges

After selecting a number of connected edges (either manually or by using Select Edges by Break Angle tool), the edges can be combined into a single curved edge (represented by Cubic Hermite spline). This operation is done by pressing Combine Selected Edges button (combineedges). Selected edges will be replaced with a single curved edge which may contain multiple control points (used to specify local curvature).

To adjust how closely a new curved edge mimics the original edges, adjust the tolerance for combining edges (click the nearby combedgedropmenu button). The tolerance affects the number of control points on the new edge and therefore local curvature. The smaller the tolerance, the closer the new edge will mimic the original geometry, but it may have a large number of control points.

Combining edges is available only when two or more edges are selected.

The animated image below shows an example of a workflow for automatically creating edges from the background geometry while using a specific default zone length and combining tolerance.

../../../../../../../_images/auto_edge_creation.gif