Blender notes to self: General

This post was written by eli on October 5, 2018
Posted Under: Blender and 3D

As I use Blender only occasionally, I’ve written down quite a few hints to myself for getting back to business. If this helps anyone else, so much better.

I’ve also written two similar posts on this matter: A  post on 3D printing and a post on rendering and animation.

Random notes

  • First off all: File > User Preferences > Input and set Orbit Style to Trackball (and not Turntable). The default (Turntable) keeps the Z axis always up, which is extremely limiting for proper modeling.
  • For a realistic look, go for the Cycles render engine. Otherwise (in particular simplistic animations and modeling), stay with Blender’s original.
  • Window > Duplicate Window for a new window with the same project, which can be organized completely differently (the content, modes, selections etc. remain in sync, but not the window layout). If you save the project, all windows will be opened the next time the project is opened.
  • Always pay attention to possible hints at the bottom of the 3D view, in particular in interactive operations with the mouse.
  • Enable / Disable cursor and grid in 3D view: In the Properties tool shelf, under Display toggle “Only Render” check box.
  • Adding a mesh in Object Mode adds an object. Adding a mesh in Edit Mode adds the mesh to the current object.
  • 3D graphics can be defined by meshes or NURBs. Both methods are available in Blender, but keep in mind that it ends up as a mesh when exported to STL for printing.
  • For easier interface, pick File > User Preferences, select Interface tab and enable “Rotate Around Selection”. Otherwise the 3D viewport’s rotation is pretty annoying.
  • Vertices = points. Edges = lines between points. Faces = 2D planes between edges + a normal vector defining its direction (see Wikipedia). If the vertices of a face aren’t coplanar, it’s drawn as separate triangles.
  • There’s an “Object” button on the Properties subwindow, containing the properties of the Object: Position, rotation, locks, transparency, you name it.
  • When quitting blender, the current design is saved as quit.blend. Use File > Recover last session to resume next time.
  • Local coordinates are applied relative to the object’s parent coordinates, so there’s a tree of coordinate displacements.
  • Pay attention to the view type, as stated at the 3D view’s top left. In particular, if it’s Local view, only the selected objects are seen. Note the plural. It’s possible to select several objects and see them all, but Edit Mode only applies to one of them.
  • When drawing a mesh for a smooth surface, keep it uniform; don’t make dense extrusions to catch the details, but fix that at a later stage. See “Subdivision Surface” below.
  • There’s a Manipulate only center of points icon at the bottom of the 3D view: Good for rotating or scaling several object as a way to only move them, but if it’s on, manipulating a single object does nothing.
  • An object may contain meshes with no connection between them.
  • “Linked” = connected through vertices (what you’d naturally call a “thing”).
  • It’s a good idea to remove double vertices every now and then: Edit mode, Vertex selection mode, select all vertices, Mesh > Vertices > Remove Doubles. This can be a result of an Extrusion canceled with Esc. Do this in particular if Subdivision Surface creates some ugly stuff for no apparent reason. Also try Mesh > Clean Up > Delete Loose.
  • There are several constraints that can be applied. Some are self-related, and some to other objects: One object’s transforms are copied to another, one limiting the other. Not all are applicable for the simple (e.g. non-Game Engine) use.
  • In order to view objects with transparency (with Cycles), viewport shading should be Material, and mix a diffuse shader with a Transparent Shader in the material (in the Node Editor). In the material tab of the object, set Viewport Alpha to “Alpha Blend”.
  • In the Properties column, there’s a section for “Mesh Analysis” which paints different faces depending on various criteria. For example, find intersections, sharp regions etc.

Checklist when weird things happen

In Edit Mode, with all selected

  • Mesh > Clean up > Delete Loose
  • Mesh > Vertices > Remove Doubles
  • Mesh > Normals > Calculate Outside

If there are sharp spots or a point getting buried, reduce subdivision surface to zero, and then rise it gradually. Look for

  • A face that shouldn’t be there (in particular an internal face)
  • An edge to a far point
  • Two very close vertices that appear to be one
  • A double vertex, edge or face (these are the most difficult to spot). Possibly by selecting by region in Wireframe view, and verifying that the correct number of elements are selected.

Cheat sheet

  • Spacebar = search functions. The ultimate cheat.
  • Use N and T buttons to toggle visibility of the properties bar and Toolshelf, respectively.
  • Fetch an object (or other resource) from another Blender File: Top menu > File > Append and find the relevant object by its name (it’s good to have then named properly…)
  • Select and move around stuff: Right-click on object and move mouse. Left-click to fix in place. Also use G key (Grab).
  • Lasso selection: CTRL + Left mouse button. For deselect, Shift + CTRL.
  • There’s also Border Select and Circle Select (under the Select menu). Pay attention to the “Limit Selection To Visible” button next to the Vertices/Edge/Face selection trio buttons.
  • Left click moves 3D cursor. Used as the landing point for added objects and as a pivot point if so chosen. In Solid 3D viewport shading, the depth element of the cursor’s position is where a ray of light would have hit a an object as visible (or somewhere near, if there’s no object on the way). This is slightly inaccurate (a tolerance of 1/10000 measure units or so) so it may be better to use Snap > Cursor to active.
  • Tilt-rotate view (just like a 2D image): Shift-Ctrl scroll mousebutton
  • To rotate view around 3D cursor: In the Properties shelf (press N), View > Lock to Cursor
  • Zoom in and out: Scroll button
  • Move scenery: Ctrl-scroll or Shift-scroll. Or: Shift-hold middle button and move mouse.
  • Rotate scenery: Press scroll button and move mouse around
  • Local View is extremely useful when the scenery becomes full with object (in particular light emission planes): Select the object to work with, and press numpad “/” (or View > View Global / Local) with the cursor on the relevant 3D view pane. This modification is relevant only to the certain pane, so other 3D views remain intact (important when some show render previews).
  • “View Selected” (numpad “.”). Puts the selected item in the view’s center instead of trying to get that manually. Useful when selecting from object hierarchy.
  • “Hide selected” (H) and unhide all (Alt-H). Get things out of view, in particular in Edit Mode (hide certain faces so one can see through). Works the same in Object Mode, but it’s equivalent to toggling the eye icon in the hierarchy.
  • Delete stuff: X gives a menu
  • Add objects: Add menu at the bottom left. Note that in Edit Mode, only meshes can be added, and the mesh is added to the selected object (not as a separate one!), as if it was a separate object Joined into one.
  • Manually setting coordinates: Press N and look in the Transform submenu. “Local” coordinates means relative to the object’s own origin, and it’s quite useful.
  • Setting an object’s parameters immediately after Adding it: Press T.
  • Note the Object Mode vs Edit Mode at the bottom left: Selection of objects is possible only on Object mode.
  • Modifiers: The wrench icon in the Properties pane (usually to the right). Can be stacked up, turned on/off momentarily, so don’t necessarily apply them right away.
  • The common editing is done in 3D view (note the small selection boxes to the left, close to the bottom).
  • View modes: At the bottom, next to “Object / Edit Mode”: Usually Solid, but Wireframe is informative, and Rendered can be nice (involves light)
  • View menu: Useful for swapping Orthographic / Perspective view, and also to view from bottom, top, side etc. Most of these accessible from Numpad (see hints in menu).
  • Make an object the center for rotation and scaling: View > View Selected
  • Specials menu: W (for subdivide, which allows e.g. subdividing a face)
  • Arbitrary vertices with edges between them: Enter Edit Mode for an object (possibly a dummy one, which is immediately deleted). Pick Vertex selection mode, and add vertices with CTRL+left mouse button. Useful along with an Empty Image (which can be semi-transparent) as a reference image.
  • To make a 2D object -> 3D, possibly spin it (see Tool Shelf).
  • Duplication of object: The Array Modifier (under “Generate”). For 2D/3D duplication, just cascade the modifiers.
  • Mesh > Edges > Bridge Edge Loops is good for filling gaps.
  • But even better, use Dissolve rather that Delete for getting rid of Vertices / Edges / Faces, so the holes aren’t created in the first place.
  • The Mirror modifier makes it easy to create symmetric objects. When used with Subdivision Surface, be sure to set align all edges on the symmetry plane: Either by scaling to zero with the symmetry plane as the pivot point, or use the Boolean modifier against a large cube, or use the Shrinkwrap modifier against a cube with the outer vertices belonging to the effective vertex group.

Distorting objects

  • Scale, Grab, and Rotate: In Edit or Object mode, select an object and press S, G and R respectively. Or add X, Y, or Z for a constrained rotation and scaling (e.g. SX or shift-X for only ZY). Also use numbers (e.g. S0.5 and R90). Hold down shift for precision.
  • Alternatively (sometimes better): Enable the transformation manipulators with the colored axis icon at the middle-bottom of the 3D view window. Then pick the type of manipulation (translate, rotate or scale) and the axis context (global, local or others). This allows for a simple manipulation across one axis (drag the manipulators).
  • Change the Pivot Point (at the bottom of 3D view) for one-side scaling or rotating around something else than the center.
  • To change the Origin of the object (for scaling or rotating), pick Object > Transform > Origin to… (e.g. 3D cursor). Only in Object Mode.
  • Align vertices to a plane or line: Move the 3D cursor to the desired position, set the Pivot Point to the cursor, select the vertices to align. Then choose S with one of the axes, and press the “zero” button — scale to zero = no distance.
  • Moving stuff: Change to Edit Mode (Bottom left menu). A few items to the right, there’s what to select: Vertex, Edge or Face select. Choose Edge or Face. Select an Edge or Face and move it around (with G or right-click). The displacement is two-dimensional, on the viewed plane.
  • There’s also Mesh > Edge Slide which is good for moving around an Edge loop (to give a subdivided surface emphasis on the right place)
  • There’s Select > Snap to Cursor and Snap to Cursor (Offset) which allows to move stuff to an exact position (the cursor can be moved to a selection prior to this).
  • Extrusion ( = Duplicate vertices, add edges between previous and duplicated vertices, and move the selection): Select a Face and press E, then move the new face on the perpendicular axis. Note that if it’s canceled with an ESC, the four new vertices remain, glued to the original face. Use CTRL-Z to get rid of them.
  • Extrusion with snapping: Press CTRL while moving mouse.
  • Duplicate a face, connected: Extrude, move around, and press ESC. This allow, for example, scaling the new face and possibly moving it, or extruding it again.
  • If more than one face is selected, all are extruded together.
  • If Sculpt mode is going to be used, consider the Multiresolution Modifier, which is the same as Subdivision Surface, but allows allocating a different figure for sculpting.
  • The Bevel modifier rounds off corners (slightly). The number of elements is crucial.
  • The “Adjust Edit Cage to Modifier result” (rightmost button) allows deforming the modified (i.e. smoothed) wireframe. This is actual sculpture. This requires a proper division of faces to begin with.
  • Alternatively, and probably because of a poorly constructed mesh with too many vertices, use Proportional Editing Mode, which forces changes to vertices within a region (button next to “select faces” button at the bottom of a 3D view, in Edit Mode). Use G to grab a vertex or whatever, and mouse wheel to enlarge (roll downwards, counterintuitively) or diminish (roll upwards) the region of influence. Size of influence region is given as a number at the bottom. There are various patterns of how the neighbors are influenced.
  • There’s also the Hook modifier, doing the same as proportional editing.
  • To add loops of vertices: CTRL-R in Edit mode, and roll the scroll button to get several loops. Left click to confirm where the loop goes. Or subdivision edges (under Mesh > Edges).
  • To cut an object in two: Add a loop with CTRL-R, and then Mesh > Vertices > Rip.
  • Or just cut: Select a few vertices, and Mesh > Vertices > Rip. It duplicates the vertices, but doesn’t connect them with edges.
  • Giving thickness to a mesh: Mesh > Faces > Solidify (there’s also a Solidify modifier)
  • To make sharp ends, extrude a face, and Mesh > Vertices > Merge (in Edit Mode, of course).
  • Free bending objects: Create a Bezier path (Add > Curve > Path) and add the Curve modifier (under distort). The object is bent along the curve
  • Closing small gaps between different objects (e.g. shoe to lower leg, or a drop of water slipping down on a surface): Apply the Shrink Modifier on the outer object (nearest Surface point is probably best), but only to a vertex group belonging to the interface region. Weight painting is useful here. Note that there’s no real meaning to “shrinking” — this is just vertices being glued to each other.

The Subdivision Surface Modifier and Catmull-Clark

  • If a smooth surface is desired, this is very likely to be used.
  • Watch this video. Really. Also Pixar’s page on this subject.
  • The Subdivision Surface modifier smooths the object by cutting each edge into two for each subdivision round, hence multiplying the number of faces by four. The mesh turns into a quads-only mesh after the first round. If there are non-quads in the original mesh, artifacts may occur on this first round, when non-quads (in particular n-gons with an uneven n) are split into quads.
  • Use quads whenever possible, and avoid vertices with more than 5 edges. Important exception: When the mesh consists of sparse”anchor points” and not a detailed outline of the desired result.
  • The positions of the added as well as moved vertices are weighted averages of a set of neighboring vertices. This causes an eroding effect on corners, turning a cube into a sphere.
  • Works best on uniformly spaced quadrilateral-faces meshes. Don’t triangulate, be careful with double vertices (e.g. from a poorly aborted extrusion) and avoid changing density of the mesh (e.g. for capturing some detail).
  • Keep the mesh minimal. It’s always possible to add vertices later. Each vertex of the mesh is a handle for deforming the curvature. Have too many of them, and it will be difficult to get a naturally smooth shape. Try to put the vertices where smooth peaks and valleys are expected, even subtle.
  • Keep the mesh minimal II: If there are small dents, rather make them as a texture with the Displace modifier, based upon a texture image (which will naturally share UV mapping with the material’s texture). This modifier should be inserted after the Subdivision Surface modifier, so it moves the final, rounded mesh. It may require a large number of subdivisions to get a smooth displacement, but that’s only necessary on the final rendering. This way, the dents are kept where they’re required, not where they were an accident.
  • Keep the mesh minimal III: If natural motion based upon bones is desired, it’s crucial to draw a (possibly curved) line of vertices that move along with the bone, and another line of vertices that stay in place. The faces between these two lines will do the stretching, and they must be laid out in a natural way, i.e. have the geometry of the skin surface that does the stretching in real life.
  • Sharp shapes will generally shrink. It will shrink less where the mesh is denser, because the averaging is done on the neighboring vertices, even if they’re close.
  • It’s possible to manipulate the move a smoothed surface in Edit mode, with effect on the original mesh with the modifier.
  • The Crease property of certain edges increases their weight in the average for calculating the vertices’ positions, ranging from 0 to 1. This makes the edge sharper after subdivision. When applied to a face, the resultant form gets close to the face (a cube turns into a cylinder if opposite faces have crease set to 1.0). Select the relevant face (in Edit mode), and press Shift-E. Or set manually in the Transform bar (Visible with N). Creasing makes the edges redder.
  • The best way to copy a smooth shape from a 2D image is to start with a subsurfaced low-count mesh, and match the smoothed shape with the 2D image’s. Then possibly apply one round of subdivision, and fine-tune. Use the crease property for sharp turns rather than adding edges if possible.
  • Unwanted creases can be a result of double edges. Select entire mesh, and go Mesh > Vertices > Remove Doubles and Mesh > Clean Up > Delete Loose.
  • Dents can be a result of an uneven mesh. Consider using Edge Loops and Dissolve Edges to get it lighter.
  • To create a sharp corner (e.g. the corner of eyes) or a pointy surface, extrude a vertex (creating an edge) and pull the vertex away from the surface. The edge, which is connected to nothing, pulls the surface towards the vertex. This edge is invisible during rendering, and isn’t cleaned up by “Delete loose” etc.

Joining / subtracting objects / making holes

  • Select two objects, and then CTRL-J. Can be separated again: Press P (Separate) in Edit mode and choose By loose parts
  • Fusing / subtracting objects (best done in Wireframe view): Select one object, pick Properties > Wrench > Add Modifier > Boolean. Within there, select Union, Difference or Intersect. It’s always with respect to another object. The “picker” object in the little Object window allows selecting the other object in the view. Once it’s fine, pick Apply.
  • The Boolean modifier messes up the mesh with duplicate vertices, and even worse, duplicate edges: Adjacent faces along the intersection may not share an edge, but instead have one of its own each. This is fairly acceptable with 3D printing, but creates warnings. Boolean is best used with simple objects for cutting. For example, a large cube to cut off parts of the modified object.
  • Fusing, the right way: Remove the intersecting faces manually, select the hole’s edges at both sides by selecting one edge for each and use Select > Edge Loops (in Edit Mode only). And then Mesh > Edges > Bridge Edge Loops.
  • The Knife tool (in the toolshelf) allows drawing straight lines, which creates new edges at the cutting points, and subdivides faces.
  • Activate Cut-Through with Z. This makes a hole in both ends.
  • There’s also Knife projection, which allows cutting a hole with a curve. Works with simple patterns.
  • Both cut-through and projection depend on the 3D viewing angle.
  • To punch a hole through a 3D body, set the shape with a 2D mesh or curve, and cut the shape on the faces on both sides. Then select the 2D holes on both sides, and pick Mesh > Edges > Bridge Edge Loops to draw edges across the body. The faces make a nice 3D hole.
  • To create an internal hole, generate the shape of the hole as a separate object, and then (in Edit Mode) Mesh > Normals > Flip Normals. Join this object with the target, and place it as desired.

Notable modifiers

  • Generate / Boolean: Create an object that is the intersection, union or difference between two objects. Excellent for chopping of a corner or even larger cuts by applying it with a large cube. Doesn’t work all that well when two complex meshes are involved, and the resultant mesh is often quite messy, and may need some work, in particular if it’s due for further manipulations. For 3D printing, this mess if often good enough, except for simple fixes.
  • Generate / Array: The way to duplicate an object.
  • Generate / Mask: Make all vertices belonging to a vertex group (or not belonging to a vertex group) invisible, both for render and editing. Extremely useful for working with complex structures, allowing to focus on certain parts (possibly internal) parts of a mesh (instead of hiding them every time).
  • Generate / Skin: Creates a body around edges (which function as an armature). A quick way to create an arbitrary 3D shape.
  • Generate / Wireframe: Gives thickness to the existing wireframe, making it a body. A bit like Skin, but simpler.
  • Generate / Triangulate: Make all faces triangles
  • Deform / Displace: Displace the vertices’ position as a function of a texture (i.e. an image). Useful for “printing text” on an object or making a bumpy surface with a certain pattern.
  • Deform / Laplace Deform: Allows deforming an object while preserving geometric properties
  • Deform / Shrinkwrap: As its name implies: pushes the vertices towards the exterior of another object, after applying its modifiers. Neat to get rid of overlapping meshes, but careful with the corners. The “Nearest Surface” (default) mode should be chosen for simple use. “Nearest Vertex” in conjunction with Vertex groups is just a way to glue vertexes from different objects together, but it’s not necessarily useful. Try both.
  • Deform / Simple Deform: Allows freehand twisting and bending and other deformations. Another (empty) object’s location, size and orientation gets different effects.

Sculpt mode

  • Excellent for fixing small dents with the “Smooth” tool (those dents that shouldn’t happen in the first place, because of a properly designed mesh…).
  • Also good for small finishes, but requires a dense mesh to work with. Use when editing with Subdivision Surface isn’t good enough.
  • Note the Brush > Sculpt Tool. “Draw” pulls up the mesh a bit (as if adding material) but if “Subtract” is chosen on the toolshelf, it dents inwards.
  • Another Sculpt Tool is “Scrape” which is good to selectively round off corner (like Bevel, just not globally).

Other modes

  • Vertex Paint: Simple, intuitive painting of the faces. For this to appear on render, a material must be assigned, and the “Vertex Color Paint” option must be checked (this isn’t the default). As expected, the paint follows the faces if they’re moved.
  • Weight Paint: An intuitive way to mark the weight of a vertex group. This has to do with Vertex Groups, an important concept for moving parts of a body along with a “bone”, as well as the Shrinkwrap modifier and other stuff. The painting applies to vertices, therefore use with subdivision and other modifiers off, and hit the right points. Subdivision surface interpolates the weights across edges between points.
  • Texture Paint: A more difficult way to paint a 3D model, but it generates a texture image one can save back. Useful for marking what goes where on the texture image, for writing back and then edit the image. Instead of fiddling with the UV mapping. Also for smoothing seams (with Clone brush). Keep the surface subdivision rate low for this. Too many faces, and the painting goes from slow to impossible.

Sources

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