Doc:FAQ/Modelling/Mesh

From BlenderWiki

Take a look at mesh glossary also.

[edit] Why are there additional edges/faces created on subdivision?

Sometimes especially when subdividing or knife-cutting additional edges/faces are created. This can be explained with the lack of n-gon (polygons with more than 4 sides) support in Blender. It is one of these things that is anchored deeply in the program-code, so don't expect this to change soon in any way.

You can however control how the distribution of the newly created faces is done. This is currently not documented in the manual itself, but here is what we have BlenderDev/EdgeSubdivision. Summary: Toggle the Subdivision method in the Dropdown (Mouseover: Choose Quad Corner Cut Type) of the Mesh Tools panel.

If you don't need to pay attention to polygon-count you can use the loop-cut (Ctrl R) to do cuts where you need them but leave only quads (if it is possible in your model).

[edit] How do I recalculate the normals?

Select all vertices with A and hit Ctrl N.

[edit] How do I cut a circular hole to a square face?

The simplest scenario:

Make a plane. Add->Mesh->Plane
Subdivide it once (W).
Extrude (E) it, but don't move it.
Scale the extrusion inwards (S).
Use To Sphere function found in Editing (F9) panel in the Mesh Tools

This way is also used in the Modelling A Cube tutorial (Make 'real' circles for the pips) - including a step-by-step with images.

See also this thread for more ways to do it.

If you want to make more complex holes, check out booleans, but mind you that they often mess up the geoemtry.

[edit] Why do I get strange black lines in my mesh in shaded view and/or the rendered image?

[edit] Normals

Maybe you created faces that have their normals pointing in the wrong direction. See #How do I recalculate the normals?.

Try pressing Ctrl N to recalculate the normals on the outside.

[edit] Redundant geometry

There is a second thing that could be wrong. Check your mesh if you have and redundant geometry (double vertices). You can do a quick W->Remove Doubles to removed most of this geometry.

[edit] Messy geometry

And another problem could be that you have geoemtry inside your mesh (extrudes edges or faces). Select & remove them and recalculate the normals again. The faces inside your mesh could have been created if you extruded a bunch of faces as "Individual Faces" in contrast to "Region"-extrude. Try it on 2 connected faces of a sphere to see the difference.

[edit] How do I model pipe-joints?

Different ways to model a pipe T-joint are listed here:

[edit] After using a boolean operation or a boolean modifier my geometry is messed up or has missing faces. Why is that?

The boolean functions in Blender are currently unusable on complex geometries. Some people have reported success with using them on simpler geometry though. This part of Blender needs a major overhaul, so if you need this feature on a daily basis i suggest checking out the bugtracker (search for "boolean") and state your opinion there.

As a workaround until then you can try using the script as posted in the following thread: 'Nonsolid' and messed up geometry after boolean operation (see the end of the thread)

[edit] Why do i see some faces in ObjectMode & render, but when i enter Editmode ([TAB]) there is nothing there?

It's quite simple, the geoemtry is hidden. You most probably pressed H somewhere in your editing process while having this exact geometry selected. This will hide it in Editmode.

EditMode: To make the geoemtry visible again press Alt H or select Mesh >> Show/Hide Vertices >> Show Hidden
ObjectMode: You can make the hidden vertices visible (in Solid, Shaded, or Textured view-mode) by clicking on the icon in the bottom right of the viewport. See also the Help, I can only select visible vertices? thread.

[edit] How do I add a single vertex object?

You can't. Add a plane and delete three vertices, instead. To add a single vertex object at the cursor location, add a cube or plane and select all vertices. Pressing Alt M >> To center will merge all the vertices into a single vertex in the center of the selection, which is the cursor location (and global center) in the default scene.

Additional Note

To add new vertices to your existing geometry (or other geoemtry similar to your selection) just ...

Select a vertex (or more geometry) and
Ctrl LMB click to your target location.
Enjoy

[edit] How do I model a Spring or Screw-like geometry?

There is a function in Blender called "Screw" in the Buttons-window (Panel: "Mesh Tools") in EditMode. Read more about the Screw tool here:

1 and here ...
Manual: Basic Mesh Tools - Screw

[edit] I want to keep some edges sharp when using the subsurf Modifier. How do i do that?

Select the edge(s), press Shift E ("Crease SubSurf") and move the mouse until you get the desired sharpness. Alternatively you can create additional geometry around the edge(s) (e.g. edgeloops).

keeping some sharp edges after subsurfing forum thread

[edit] Why can I see through my mesh while I am in solid view mode?

Because you don't have "Limit selection to view" button toggled. You can find this button next to selection modes in the 3D viewport header.

[edit] What can I do with 'Crease' (Shift+E)?

You use Crease SubSurf (Shift E) to determine the sharpness of edges after applying the SubSurf Modifier. See Manual/Subsurf for more info.

[edit] How do I align vertices on specific axis?

Select vertices to be aligned shift+( RMB )
Hit S to scale and then hit the button for the axis in which you want to align them. (e.g X, Y or Z) See Manual/Axis Locking for more info.
After that hit 0 and finish with Enter (or LMB ).

[edit] How do I align objects on specific axis?

Enable "Move object centers only" in the 3D viewport header.
Select objects to be aligned.
Hit S to scale and then hit the button for the axis in which you want to align them. (e.g X, Y or Z) See Manual/Axis Locking for more info.
After that hit 0 and finish with Enter (or LMB ).

[edit] How do I increase/decrease the diameter of a tube-like geometry?

Select the tube-geoemtry
Alt S + drag the mouse to scale

[edit] How do I make part of my geometry into a separate object?

See FAQ/Modelling

Blender FAQ: Index | Questions | Manual | Blender Version 2.42a