An edge ring is a path of polygon edges that are connected in sequence by their shared faces. An edge loop is a path of polygon edges that are connected in sequence by their shared vertices. Edge ring and edge loop selections let you select several edges across a polygon mesh without having to select each edge individually. For more information on how to use these features see and .
The Select Edge Loop Tool and Select Edge Ring Tool, as well as the Offset Edge Loop Tool and the Insert Edge Loop Tool, use a variety of criteria for the selection of the various edge types. Understanding these criteria can help you troubleshoot an issue when an edge selection doesn’t occur as you expect.
Select Edge Ring Tool uses a selection criteria that is primarily based on four-sided polygons (quads) within the mesh. That is, when you perform a double-click selection on an edge you will be able to accurately predict the resulting edge selection when the mesh is comprised of four-sided polygons.
When you double-click to select a ring (path) of edges on the mesh, all adjacent edges in either direction of the initial edge selection also get selected along the same contour line of the mesh. The selection only stops when it cannot determine a corresponding adjacent edge on the shared face or when it reaches the end of the mesh.
When the tool cannot accurately determine which direction to continue the selection or when the four-sided condition is not being met, you need to manually click the next desired edge to determine the direction of the selection path and continue the selection.
Select Edge Loop Tool uses a selection criteria that is based on the number of edges that are connected to a single vertex (referred to as the valency). The number of edges attached to a vertex for a selected edge must equal four (Valency = 4) in order for a loop selection to occur.
If you perform a double-click selection and two paths of selected edges appear unexpectedly, this usually indicates that the configuration of the four-sided polygons has one or more faces that are shaped in a diagonal fashion. As a result, the edge selection will deviate by continuing in a different direction. One example of this is when two locator lines appear on a single mesh to indicate that the selection has resulted in a U-shaped selection on the polygon mesh (see diagram below).
Some polygon configurations are problematic for the edge ring and edge loop selection and splitting tools. That is, the selection of edges will not occur as you expect, or the selection will cross a face in an unwanted fashion. When this occurs, you should choose an alternate selection operation. For example, manually shift-selecting the polygon edges; or using the Maya® Artisan ™ tools to paint a selection. When you need to insert edges on the polygon mesh and the current topology varies drastically, you can manually split the mesh using the to avoid producing unexpected results.
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