Selecting in Edit Mode

At first glance, this is a trivial subject, but in fact there are a lot of options that are not a first apparent. Some more useful than others.

We will start with the basics. In Edit mode, click on a vertex to select it. Click elsewhere and it will be deselected. [Shift]-Click on another vertex, and any selected vertex will remain selected, and the new one as well.

Note: Most of this applies to edges and faces too.

Some of it applies to Object mode too. I do not find there are the same issues in Object mode, as I might only have a couple of dozen objects, while one object might have hundreds of vertices.

Toolbar

Top left of the toolbar is the select tool. If you click and hold on it, you will see there are four option.

Tweak: With Tweak you select each vertex as normal, but can then move it. It is only slightly different to the move tool, and frankly probably only useful for doing minor adjustments to organic models. I have never used it.

Select Box: This is the one I use most by a long way. Just drag to create a box; all points inside the box will be selected. Note that it the view is not X-ray, only the vertices you can see will be selected.

Select Circle: Your cursor is now a circle. If you drag the mouse, all vertices that go inside the circle will be selected.

Select Lasso: Similar to the box, drag to create a region, and whatever is inside the region is selected. However, the region is defined by the shape you draw while dragging - with a straight line back to the start.

Vertex Groups

Applies only to vertices obviously.

In the Properties window there is a Data tab, and at the top Vertex Groups. Click on the plus sign to create a new group. Double click the name to call it something else  - or leave it as Group, if it is the only one for this object.

Now select some vertices, and click Assign. The selected vertices will be added to the group. You can add as many times as you want; the group will accumulate all of them. There is a Remove button so you can delete them from the group.

Once you have a group set up, click Select to have all the vertices in the group selected - in addition to any already selected. If you want all the vertices not in the group, press A to select all, then click Deselect.

Vertex groups are used in some modifiers and other contexts, and are probably more important there, but are useful if there is a specific part of the model that you repeatedly want to select.

Select Menu

All: Select them all. I prefer to just press A.

None: None are selected. I prefer to click away from anything.

Invert: Selects any unselected and deselects any selected.

Box/Circle/Lasso: these are as above, but just temporarily. For box and lasso, it is just for one selection. For circle it is until you right-click. Lasso gives you extra options to add, subtract, etc.

Mirror: All existing selected vertices are deselected, but their mirror counterparts - if it exists - will be selected. Struggling to think when this would be useful.

Select Random: Random vertices are selected. Again, why?

Checker Deselect: Vertices are deselected supposedly in a check pattern, but not always. If you want to select every nth face or edge round a cylinder you could use this, but frankly not much use.

More/Less: Use More to additionally select all connected vertices. Less does the reverse.

Select Similar

The next few are more complicated, but can be very useful. They all select any vertices that are similar to the already selected ones. There are four useful options.

Normal: The normal is a line (a vector technically) pointing out from the face. This will select all vertices with the same normal, i.e., facing the same direction.

Amount of adjacent faces: If the currently selected vertex has four adjacent faces, this will select all the vertices with four adjacent vertices.

Vertex groups: Selects all vertices that share a vertex group with the currently selected.

Amount of connecting edges: If the currently selected vertex has four connecting edges, this will select all the vertices with four connecting edges.

Select all by trait

These all select the vertices that have a specific trait. I use the first two a fair bit when doing a slate roof, and I have had to delete a section, to make sure there are no partially deleted slates.

Non-manifold: Selects vertices/edges/faces that are not quite right. There are six types of wrongness, and you can pick which you are interested in. An object will only print if it is manifold.

Loose geometry: Selects vertices or edges not connected to a face, or faces not connected to other faces.

Interior faces: All faces where each edge has more than two faces.

Faces by sides: All vertices of faces with (by default) four sides

Poles by count: A pole is a vertex with three, or five or more edges. seems to be something generally to be avoided, but that may not be relevant to 3d printing.

Select linked

These tools will select all the vertices that are connected to the currently selected one.

Linked: All vertices that are connected; useful and has a shortcut, [CTRL]-L.

Shortest path: Vertices forming a continuous path between the last selected and the previous.

Linked flat faces: All vertices that are connected and in the same plane.

Select loops

It was discovery of these tools that inspired this post. You need to select two vertices at each end of an edge - or an edge.

Edge loop: This finds edges that follow the direction of the first edge.

Edge ring: This finds edges that are adjacent round the ring.