Blender 3D: Noob to Pro/More Mesh Editing Techniques

You previously scratched the surface of the tools that Blender provides for editing meshes. This page will introduce more of them.

Adding More Mesh Pieces

Start with a default cube again. Select it and  TAB  into Edit mode. Press  SHIFT + A  to bring up the Add menu; instead of all the submenus with all the objects you could add in Object mode, now you will see only a single menu containing only mesh objects. Select, say, another cube, and use  G  to move it away from the first cube.

If you  TAB  into Object mode, you will see that the two cubes look like separate, disconnected objects, but they are in fact one object, and cannot be selected separately in Object mode. You can  TAB  back into Edit mode, and make connections between the vertices of the two cubes, which you cannot do with separate objects. Therefore:

A single mesh object can be made of separate, disconnected pieces.

 

Linked Selections

If you have some part of a mesh selected, pressing  CTRL + L  will select all other parts of the mesh that are connected to the already-selected parts. In the above case of the object made up of two disconnected cubes, you can  RMB  on a single vertex of one cube, then use  CTRL + L  to select all the rest of that cube but not the other.

Another way to do linked selections is to simply move the mouse over some part of the piece you want to select, and press  L  to immediately select everything connected to that.

Separating and Joining Meshes

You can separate a part of a mesh into its own object. The part you are separating doesn’t have to be disconnected from the rest of the mesh. Simply select the part you want to separate in Edit mode, and press  P , and in the menu that appears, choose “Selection”. You will see the selected part immediately change to a reddish-orange highlight, indicating it is part of the object selection but not the active object.

Conversely, you can join two or more mesh objects into one. Select all the desired objects in Object mode, and press  CTRL + J , and you will see them all immediately take on the orangey-yellow highlight indicating they are all the active object.  TAB  into Edit mode, and you can confirm that you can now edit them all as part of the same mesh object.

Proper Extrusion

You previously discovered how to add whole new sections to a mesh with  CTRL + LMB . Blender also has a proper Extrude function, which lets you do this with a bit more control.

Start with the default cube, as usual. Go into Edit mode. Select just the top four vertices. Press  E  to start extruding, and move the mouse roughly along the direction of the Z-axis. You will find yourself dragging out a whole new face formed from four new vertices connected to the ones you previously selected. You will notice also that the movement of the newly-added part of the mesh is automatically constrained to be parallel to the Z-axis. Press  LMB  or  ENTER  to finish the extrusion operation.

Deselect everything. Now try selecting another four vertices of the original cube, say making up a face pointing along the X-axis. Now if you extrude these, you will see that the extrusion is automatically constrained to move only parallel to the X-axis.

A quirk of the extrusion function is that if you press  E  and then immediately abort with  RMB  or  ESC , the additional mesh piece is still created, but it is left in the same position as the original mesh. To really abort the extrusion, you have to undo it with  CTRL + Z .

Loop Cuts

Ensure you are in Edit mode. It doesn’t matter what parts of the mesh are currently selected. Press  CTRL + R  to activate the Loop Cut function. You will see a magenta-coloured loop wrap itself around different parts of the mesh as you move the mouse. You can press  RMB  or  ESC  to abandon the operation at this point, or once you see the loop appearing around the right part of the mesh, you can use  LMB  or  ENTER  to proceed. Now the magenta colour changes to the usual orange-yellow selection highlight, and will now restrict itself to sliding along this section of the mesh as you move the mouse. If you press  LMB  or  ENTER  at this point, you will end up with a new loop of vertices and edges at the last-shown point, while  RMB  or  ESC  will still create the new loop, but leave it positioned at the midpoint.

When the loop is still at the magenta stage, you can use the mouse wheel to increase the number of cuts to 2 or more. However, once you confirm this with  LMB  or  ENTER , you are not given the choice to position the multiple cuts; they will always be positioned at equal distances along that portion of the mesh

Subdividing Parts

A loop cut always cuts a complete loop. Alternatively, you can subdivide just a selected part of the mesh: make your selection, then press  W  to bring up the Vertex Specials menu, and select the top option, “Subdivide”. This will create one cut, but a panel will appear at the lower left of the Toolshelf ( T  to make it visible at the left of the 3D view if it’s not), where you can alter the number of cuts and other settings.

Another option is the second one on the  W  menu: “Subdivide Smooth”. This one computes a Catmull-Clark interpolation to give more of a curve rather than a flat subdivision.

Subdivision Surface Modifier

A modifier causes some change to the geometry of an object just before it gets rendered. The change does not affect the object as you view and edit it in the 3D view, or as it is stored in the document (unless you apply the modifier, which makes the change permanent). This allows you to create some complicated effects at render time, while the original mesh stays simple and easy to edit. Modifiers for the active object are applied and controlled in the Modifiers tab in the Properties window.

A subdivision surface modifier (also known as a “subsurf” modifier) applies the Catmull-Clark interpolation discussed above as a modifier. Being a modifier, it applies to the entire object, not just to selected vertices. But since the original mesh is preserved, you use it as a control cage to adjust the shape of the interpolated curve.

Start with the default cube selected in Object mode, as usual. Go to the Modifiers tab in Properties. When you select “Subdivision Surface” from the “Add Modifier” menu, a new panel appears as at right. Notice the two value sliders under the “Subdivisions”: heading; 'View' controls the level of subdivision within the 3D view, while 'Render' applies to the actual render; the higher the number of levels, the closer to a curve the interpolated geometry becomes. Having two separate settings for working environment and render allows for faster operation in the 3D view, with the usual tradeoff of lower quality, while still allowing maximum quality for the final render.

Keyboard shortcuts: Because the Subdivision Surface modifier is so heavily used, there is a set of hotkeys for adding the modifier to the current object if it doesn’t already have one, and setting the number of subdivision levels in the 3D view:  CTRL + 1KEY  ..  CTRL + 5KEY  for setting the view levels to 1 .. 5 respectively.

 

As soon as you add the modifier, the appearance of the cube should change to look something like at right (here shown with just one level of subdivision).

The upper part of the panel (from the “Apply” and “Copy” buttons upwards) is common to all modifiers. Note the X button at the right: clicking this gets rid of the modifier. Notice also in here a group of 4 icon buttons in the middle, the leftmost two looking like a camera and an eye: the meanings of these are as follows:

• Actually use the modifier during rendering
• Show the modifier effect in the 3D view
• Show the modifier effect in the 3D view in Edit mode (if this is unchecked while the previous one is checked, then the modifier effect disappears while in Edit mode)
• Show the mesh as though the modifier were applied to it when in Edit mode.

Unchecking the first one lets you disable the modifier without losing its settings, while the remaining three can be handy if you’re trying to disentangle the effects of different modifiers during editing.

When the third button is enabled, the mesh will look like this in Edit mode: the original mesh remains highlightable and editable, while a preview of the effect of the modifier is also visible, and responds immediately to any changes made to the original mesh. (Try moving some vertices around, and see what happens.)

The fourth button goes one step further, and pretends the modifier has already been applied, while still only allowing you to edit parts corresponding to the original mesh.

Sharpening the Curves

The subdivision surface modifier offers a lot more control over the resulting shape than might be apparent from above. For example, you might not want uniform curvature everywhere, you want some parts of the shape to have sharper edges. This can be achieved by strategic positioning of additional vertices in the control-cage mesh.

For example, start with the subdivided cube example as above. Press  CTRL + R  to start a loop cut, and position the magenta outline something like this:

Press  LMB  or  ENTER  ...

... and move the mouse so the newly-added loop moves closer to one side of the cube. See how the subdivided mesh develops a sharper curve on this side?

To confirm the placement of the new loop, press  LMB  or  ENTER  once more.

The basic principle is:

The closer together the control vertices are, the sharper the subdivided curve.