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Selecting Edges

Edge selection can be done with simple, “universal” tools described in the basics page. However, when modeling, you will often need some more powerful ways to select your them. One of the most useful one selects edges based on the loops they form. Let’s see this in detail.

Edge Loop Selection

Mode: Edit mode → Vertex or Edge select mode

Hotkey: AltRMB Template-RMB.png or CtrlE » 7 NumPad (based on existing edge selection)

Menu: Select » Edge Loop (based on existing edge selection)

Description

Holding Alt while selecting an edge selects a loop of edges that are connected in a line end to end, passing through the edge under the mouse pointer. Holding Alt⇧ Shift while clicking adds to the current selection. Edge loops can also be selected based on an existing edge selection, using either Select » Edge Loop, or the Edge Loop Select option of the Edge Specials menu (CtrlE).

Vertex mode
In Vertex select mode, you can also select edge loops, by using the same hotkeys, and clicking on the edges (not on the vertices).


Examples

Longitudinal and latitudinal edge loops.

The left sphere shows an edge that was selected longitudinally. Notice how the loop is open. This is because the algorithm hit the vertices at the poles and terminated because the edge at the pole connects to more than three other edges. However, the right sphere shows an edge that was selected latitudinally and has formed a closed loop. This is because the algorithm hit the first edge that it started with.

Technical Details

The algorithm for selection is as follows:

  • First check to see if the selected element connects to only 3 other edges.
  • If the edge in question has already been added to the list, the selection ends.
  • Of the 3 edges that connect to the current edge, the ones that share a face with the current edge are eliminated and the remaining edge is added to the list and is made the current edge.


Edge Ring Selection

Mode: Edit mode → Edge select mode

Hotkey: CtrlAltRMB Template-RMB.png

Menu: Select » Edge Ring (based on existing edge selection)

Description

In Vertex or Edge select mode, holding CtrlAlt while selecting an edge selects a sequence of edges that are not connected, but on opposite sides to each other continuing along a face loop.

As with edge loops, you can also select edge rings based on current selection, using either Select » Edge Ring, or the Edge Ring Select option of the Edge Specials menu (CtrlE).

Vertex mode
In Vertex select mode, you can use the same hotkeys when clicking on the edges (not on the vertices), but this will directly select the corresponding face loop…


Examples

A selected edge loop, and a selected edge ring.

In (A selected edge loop, and a selected edge ring), the same edge was clicked on but two different “groups of edges” were selected, based on the different commands. One is based on edges during computation and the other is based on faces.

Technical Details

Edge ring selection is based on the same algorithm as in Face Loop Selection, though the end results differ as only some edges are selected.

Loop to Region and Region to Loop

Mode: Edit mode → Edge select mode

Hotkey: CtrlE » 9 NumPad and CtrlE » 0 NumPad

Menu: Select » Loop to Region/Region to Loop

Description

Loop to Region examines the current set of selected edges and separates them into groups of “loops” that each bisect the mesh into two parts. Then for each loop it selects the smaller “half” of the mesh. Even though it works in Vertex and Face select mode, the results using these might be strange – you should stick to Edge select mode…

Region to Loop is the “logical inverse” of Loop to Region, based on all regions currently selected, it selects only the edges at the border of these regions. It can operate in any select mode, but always switch in Edge select mode when applied.

All this is much more simple to illustrates with examples:

Examples: Loop to Region

Selection.
Loop to Region.
Selection.
This tool handles multiple loops fine, as you can see.
Selection.
This tool handles “holes” just fine as well.


Example: Region to Loop

Selection.
This is the “logical inverse” of loop to region.


Menu Options

As we saw in advanced selection page, there are some options of the Select menu (3D View header) that specifically concern edges.

We have already seen Edge Loop, Edge Ring, Loop to Region and Region to Loop above.

Sharp Edges

Mode: Edit mode → Edge select mode

Hotkey: CtrlAlt⇧ ShiftS

Menu: Select » Sharp Edges

This option will select all edges that are between two faces forming an angle less than a given value, which is asked you via a small pop-up dialog. The lower is this angle limit, the sharper will be the selected edges. At 180°, all “manifold” (see below) edges will be selected.

There are a few points to take into account here:

  • Even if this tool also works in Vertex select mode, you should only use it in Edge one (else, some edges are implicitly selected, that shouldn’t be).
  • Only manifold edges can be selected by this tool (see below for what is a “manifold” edge…), as it must be able to compute an angle between to faces!
  • This option has nothing to do with the Sharp flag of edges!


Non-Manifold

Mode: Edit mode → Edge select mode

Hotkey: CtrlAlt⇧ ShiftM

Menu: Select » Non-Manifold

This option selects all edges that are “non-manifold”. These are all edges that are not between exactly two faces (i.e. edges belonging to zero, one, three or more faces). Here again, this tool works in Vertex select mode too – but for the same reasons as above, you should only use it in Edge select mode.