Blender
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PART II
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MESH MODELLING.CONCEPT
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CH. 6 MESH MODELING
Plane A standard plane contains four vertices, four edges, and one face. It is like a piece of paper lying on a table; it is not a real three-dimensional object because it is flat and has no thickness. Objects that can be created with planes include floors, tabletops, or mirrors.
CONCEPT, BASIC EDITING, TOOLS, SUBDIVISION SURFACES, META OBJECTS
Cube A standard cube contains eight vertices, 12 edges, and six faces, and is a real threedimensional object. Objects that can be created out of cubes include dice, boxes, or crates.
The principal Object of a 3D scene is usually a Mesh. In this chapter we will first enumerate the basic mesh objects, or primitives, then follow with a long series of sections describing in detail the action which can be taken on Mesh Objects.
Basic Objects To create a basic Object press SPACE and select "Add>>Mesh", or, access the 'add'menu by pressing SHIFT-A or simply hold LMB on 3D Window, for more than half a second. Select the basic object you'd like to create from the menu. We describe every basic object or primitive you can create within Blender below. Figure 1 also shows the variety of basic objects that can be created.
Monkey UVsphere
UVSphere A standard UVsphere is made out of n segments and m rings. The level of detail can be specified in the popup window which appears when the UVsphere is created. Increasing the number of segments and rings makes the surface of the UVsphere smoother. Segments are like Earth meridians, going pole to pole, rings are like Earth parallels. Example objects that can be created out of UVspheres are balls, beads or pearls for a necklace.
If you specify a six segment, six ring UVsphere you'll get something which, in top view, is a hexagon (six segments), with five rings plus two points at the poles. Thus, one ring fewer than expected, or two more, if you count the poles as rings of radius 0.
Icosphere Cone
Cylinder
Tube
Cube
Circle
(with faces)
Grid Plane
Icosphere An Icosphere is made up of triangles. The number of subdivisions can be specified in the window that pops up when the Icosphere is created; increasing the number of subdivisions makes the surface of the Icosphere smoother. At level 1 the Icosphere is an icosahedron, a solid with 20 equilateral triangular faces. Any increasing level of subdivision splits each triangular face into four triangles, resulting in a more spherical appearance. Icosphere's are normally used to achieve a more isotropical and economical layout of vertices than a UVsphere. Cylinder A standard cylinder is made out of n vertices. The number of vertices in the circular cross-section can be specified in the popup window that appears when the object is created; the higher the number of vertices, the smoother the circular cross-section becomes. Objects that can be created out of cylinders include handles or rods.
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Circle A standard circle is comprised of n vertices. The number of vertices can be specified in the popup window which appears when the circle is created. The more vertices the circle contains, the smoother its contour will be. Examples of circle objects are disks, plates, or any kind of flat and round object.
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Tube A standard tube is made out of n vertices. The number of vertices in the hollow circular cross-section can be specified in the popup window that appears when the object is created; the higher the number of vertices, the smoother the hollow circular cross-section becomes. Objects that can be created out of tubes include pipes or drinking glasses. (The basic difference between a cylinder and a tube is that the former has closed ends.) Cone A standard cone is made out of n vertices. The number of vertices in the circular base can be specified in the popup window that appears when the object is created; the higher the number of vertices, the smoother the circular base becomes. Objects that can be created out of cones include spikes or pointed hats. Grid A standard grid is made out of n by m vertices. The resolution of the x-axis and y-axis can be specified in the popup window which appears when the object is created; the higher the resolution, the more vertices are created. Example objects that can be created out of grids include landscapes (with the proportional editing tool) and other organic surfaces. Monkey This is a gift from old NaN to the community and is seen as a programmer's joke or "Easter Egg". It creates a monkey's head once you press the Oooh Oooh Oooh button. The Monkey's name is Suzanne and is Blender's mascotte.
EditMode When working with geometric objects in Blender, you can work in two modes: ObjectMode and EditMode. Basically, as seen in the previous section, operations in ObjectMode affect whole objects, and operations in EditMode affect only the geometry of an object, but not its global properties such as the location or rotation. In Blender you switch between these two modes with the TAB key. EditMode only works on one object at a time: the active object. An object outside EditMode is drawn in purple in the 3D Windows (in wireframe mode) when selected; it is black otherwise. The active object is drawn black in EditMode, but each vertex is highlighted in purple (fig. 2). Selected vertices are drawn in yellow (fig. 3) and, if appropriate buttons in the Editing (F9) Context Mesh Tools 1 Panel are pressed (Draw Faces and Draw Edges) also selected edges and faces are highlighted.
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2
Two pyramids, one in EditMode (left) and one in ObjectMode (right).
3
Cube with selected vertices in yellow.
Structures: Vertices, Edges and Faces In basic meshes, everything is built from three basic structures: Vertices, Edges and Faces. (We're not talking about Curves, NURBS, and so forth here.) But there is no need to be disappointed: This simplicity still provides us with a wealth of possibilities that will be the foundation for all our models.
Vertices A vertex is primarily a single point or position in 3D space. It is usually invisible in rendering and in ObjectMode. (Don't mistake the center point of an object for a vertex. It looks similar, but its bigger and you can't select it.) To create a new vertex, change to EditMode, hold do CTRL, and click with the LMB. Of course, as a computer screen is two-dimensional, Blender can't determine all three vertex coordinates from one mouse click, so the new vertex is placed at the depth of the 3D cursor 'into' the screen. Any vertices selected previously are automatically connected to the new one with an edge. Edges An edge always connects two vertices with a straight line. The edges are the 'wires' you see when you look at a mesh in wireframe view. They are usually invisible on the rendered image. They are used to construct faces. Create an edge by selecting two vertices and pressing FKEY. Faces A Face is the most high level structure in a mesh. Faces are used to build the actual surface of the object. They are what you see when you render the mesh. A Face is defined as the area between either three or four vertices, with an Edge on every side. Triangles always work well, because they are always flat and easy to calculate.
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Take care when using four-sided faces, because internally they are simply divided into two triangles each. Four-sided faces only work well if the Face is pretty much flat (all points lie within one imaginary plane) and convex (the angle at no corner is greater than or equal to 180 degrees). This is the case with the faces of a cube, for example. (That's why you can't see any diagonals in its wireframe model, because they would divide each square face into two triangles. While you could build a cube with triangular faces, it would just look more confusing in EditMode.) An area between three or four vertices, outlined by Edges, doesn't have to be a face. If this area does not contain a face, it will simply be transparent or non-existent in the rendered image. To create a face, select three or four suitable vertices and press FKEY.
4
Chopped-off pyramid.
Basic Editing Most simple operations from ObjectMode (like selecting, moving, rotating, and scaling) work identically on vertices as they do on objects. Thus, you can learn how to handle basic EditMode operations very quickly. The only notable difference is a new scaling option, ALT-S which scales the selected vertices along the direction of the normals (shrinksfattens). The truncated pyramid in figure 4, for example, was created with the following steps:
1.
5
Edit Context.
All operations in Edit Mode are ultimately performed on the vertices; the connected edges and faces automatically adapt, as they depend on the vertices' positions. To select an edge, you must select the two endpoints or either place the mouse on the edge and press CTRL-ALT-RMB. To select a face, each corner must be selected.
Add a cube to an empty scene. Enter EditMode.
2.
Make sure all vertices are deselected (purple). Use border select (BKEY) to select the upper four vertices.
Edit Mode operations are many, and most are summarized in the Editing Context Buttons window, accessed via the ( ) button of header or via F9 (fig 5). Note the group of buttons in the Mesh Tools 1 Panel.
3.
Check that the scaling center is set to anything but the 3D cursor (see fig. 1 in Chapter 5), then switch to scale mode (SKEY), reduce the size, and confirm with LMB.
•
Exit EditMode by pressing TAB.
•
4.
One Extra feature for Edit Mode is the Mirroring tool. If you have some vertices selected and you press MKEY you will be presented with a Menu containing nine options. You can select from these to mirror the selected vertice with respect to any of the X,Y or Z axis of the Global, Local, or Viewing reference. One additional feature of EditMode is the CircleSelect mode. It is invoked by pressing BKEY twice instead of only once, as you would for BorderSelect. A light grey circle is drawn around the cursor and any LMB click selects all vertices within. NUM+ and NUM- or the MW, if any, enlarge or shrink the circle.
NSize - Determines the length, in Blender Units, of the normals to the faces,
if they are drawn. Draw Normals - Toggle Normals drawing. If this is ON, face normals are drawn as cyan segments. • Draw Faces - If this is ON, faces are drawn as semi-transparent blue, or as semi-transparent purple if they are selected. If this is OFF, faces are invisible. • Draw Edges - Edges are always drawn black, but if this button is ON, selected edges are drawn in yellow. Edges joining a selected node and an un-selected one have a yellow-black gradient. • All Edges - Only those edges strictly necessary to show the object shape are shown in Object mode. You can force Blender to draw all edges with this button.
Of course all these colors are customizable in the Theme editor.
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MESH MODELLING.UNDO Edit
With WKEY you can call up the "Specials" menu in EditMode (fig. 6). With this menu you can quickly access functions which are frequently required for polygon-modelling.
You can access the entries in a PopupMenu by using the corresponding numberkey. For example, pressing WKEY and then 1KEY you will subdivide the selected vertices without having to touch the mouse at all. 7
•
• •
• •
6
Specials Menu.
• • • • •
•
Subdivide - Each selected edge is split in two,
new vertices are created at middle points, and faces are split too, if necessary. Subdivide Fractal - As above, but new vertices are randomly displaced within a user-defined range. Subdivide Smooth - As above, but new vertices are displaced towards the baricentrum of the connected vertices. Merge - Merges selected vertices into a single one, at the baricentrum position or at the cursor position. Remove Doubles - Merges all of the selected vertices whose relative distance is below a given threshold (0.001 by default). Hide - Hides selected vertices. Reveal - Shows hidden vertices. Select Swap - All selected vertices become unselected and vice-versa. Flip Normals - Change the Normals directions in the selected faces. Smooth - Smooths out a mesh by moving each vertex towards the baricentrum of the linked vertices. Mirror - Same as MKEY described above.
Many of these actions have a button of their own in the Mesh Tools Panel of the Edit Buttons Window (fig. 5). The Remove doubles threshold can be adjusted here, too.
U-Key
Shift-U
Undo and Redo.
Mesh Undo
8
Undo Menu.
As for Blender 2.3 we finally have a true Undo. It works only for Meshes and only in Edit Mode. Mesh undo works in the background saving copies of your mesh in memory as you make changes. Pressing the UKEY in mesh EditMode reverts to previously saved mesh, undoing the freshly performes edit operation (fig. 7). Undo operations are only stored for one mesh at a time. You can leave and re-enter EditMode for the same mesh without losing any undo information, but once another mesh is edited, the undo information for the first is gone. Pressing SHIFT-U re-does the last undo operation (fig. 7). Pressing ALT-U brings up the undo menu (fig. 8). This lists all the undo steps by name so you can quickly find your way back to a known good point in your work. The ALT-U menu also contains the option All Changes. This option is more powerfull than merely pressing UKEY repeadetly, and will reload the mesh data as it was at the beginning of your edit session even if you have used up all your undo steps. Edit undo can be memory intensive. A mesh of 64,000 faces and verts can use over 3Mb of RAM per undo step. In case you are on a machine that is strapped for RAM, there is in the User Preference Window, under Edit Methods, a NumButton for determining the maximum number of undo steps saved. The allowed range is 1-64. The default is 32.
Smoothing As seen in the previous sections, polygons are central to Blender. Most objects in Blender are represented by polygons and truly curved objects are often approximated by polygon meshes.
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When rendering images, you may notice that these polygons appear as a series of small, flat faces (fig. 9). Sometimes this is a desirable effect, but usually we want our objects to look nice and smooth. This section shows you how to smooth an object, and how to apply the AutoSmooth filter to quickly and easily combine smooth and faceted polygons in the same object. There are two ways to activate Blender's face smoothing features. The easiest way is to set an entire object as smooth or faceted by selecting a mesh object, in ObjectMode, switching to the Editing Context (F9), and clicking the Set Smooth button in the Link and Materials Panel (fig. 10). The button does not stay pressed, but forces Blender to assign the "smoothing" attribute to each face in the mesh. Now, rendering the image with F12 should produce the image shown in figure 11. Notice that the outline of the object is still strongly faceted. Activating the smoothing features doesn't actually modify the object's geometry; it changes the way the shading is calculated across the surfaces, giving the illusion of a smooth surface.
9
Simple un-smoothed test object.
11
Same object as in fig. 9, this time completely smoothed by 'Set Smooth'.
10
Set Smooth and Set Solid buttons of EditButtons context.
12
Object in editmode with some faces selected.
Click the Set Solid button in the same Panel to revert the shading to that shown in figure 9. Alternatively, you can choose which faces to smooth by entering EditMode for the object with TAB, then selecting the faces and clicking the Set Smooth button (fig. 12). When the mesh is in editmode, only the selected faces will receive the "smoothing" attribute. You can set solid faces (removing the "smoothing" attribute) in the same way: by selecting faces and clicking the Set Solid button. It can be difficult to create certain combinations of smooth and solid faces using the above techniques alone. Though there are workarounds (such as splitting off sets of faces by selecting them and pressing YKEY), there is an easier way to combine smooth and solid faces, by using AutoSmooth. Press the AutoSmooth button in the Mesh Panel of the Edit Buttons (fig. 13) to tell Blender to decide which faces should be smoothed on the basys of the angle between faces (fig. 14). Angles on the model that are sharper than the angle specified in the Degr NumBut will not be smoothed. Higher values will produce more smoothed faces, while the lowest setting will look identical to a mesh that has been set completely solid. Only faces that have been set as smooth will be affected by the AutoSmooth feature. A mesh, or any faces that have been set as solid will not change their shading when AutoSmooth is activated. This allows you extra control over which faces will be smoothed and which ones won't by overriding the decisions made by the AutoSmooth algorithm. 13 AutoSmooth button group in the
EditButtons context.
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14
Same test object with AutoSmooth enabled.
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MESH MODELLING.CONCEPT
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CH. 6 MESH MODELING
Plane A standard plane contains four vertices, four edges, and one face. It is like a piece of paper lying on a table; it is not a real three-dimensional object because it is flat and has no thickness. Objects that can be created with planes include floors, tabletops, or mirrors.
CONCEPT, BASIC EDITING, TOOLS, SUBDIVISION SURFACES, META OBJECTS
Cube A standard cube contains eight vertices, 12 edges, and six faces, and is a real threedimensional object. Objects that can be created out of cubes include dice, boxes, or crates.
The principal Object of a 3D scene is usually a Mesh. In this chapter we will first enumerate the basic mesh objects, or primitives, then follow with a long series of sections describing in detail the action which can be taken on Mesh Objects.
Basic Objects To create a basic Object press SPACE and select "Add>>Mesh", or, access the 'add'menu by pressing SHIFT-A or simply hold LMB on 3D Window, for more than half a second. Select the basic object you'd like to create from the menu. We describe every basic object or primitive you can create within Blender below. Figure 1 also shows the variety of basic objects that can be created.
Monkey UVsphere
UVSphere A standard UVsphere is made out of n segments and m rings. The level of detail can be specified in the popup window which appears when the UVsphere is created. Increasing the number of segments and rings makes the surface of the UVsphere smoother. Segments are like Earth meridians, going pole to pole, rings are like Earth parallels. Example objects that can be created out of UVspheres are balls, beads or pearls for a necklace.
If you specify a six segment, six ring UVsphere you'll get something which, in top view, is a hexagon (six segments), with five rings plus two points at the poles. Thus, one ring fewer than expected, or two more, if you count the poles as rings of radius 0.
Icosphere Cone
Cylinder
Tube
Cube
Circle
(with faces)
Grid Plane
Icosphere An Icosphere is made up of triangles. The number of subdivisions can be specified in the window that pops up when the Icosphere is created; increasing the number of subdivisions makes the surface of the Icosphere smoother. At level 1 the Icosphere is an icosahedron, a solid with 20 equilateral triangular faces. Any increasing level of subdivision splits each triangular face into four triangles, resulting in a more spherical appearance. Icosphere's are normally used to achieve a more isotropical and economical layout of vertices than a UVsphere. Cylinder A standard cylinder is made out of n vertices. The number of vertices in the circular cross-section can be specified in the popup window that appears when the object is created; the higher the number of vertices, the smoother the circular cross-section becomes. Objects that can be created out of cylinders include handles or rods.
1 96
Circle A standard circle is comprised of n vertices. The number of vertices can be specified in the popup window which appears when the circle is created. The more vertices the circle contains, the smoother its contour will be. Examples of circle objects are disks, plates, or any kind of flat and round object.
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Tube A standard tube is made out of n vertices. The number of vertices in the hollow circular cross-section can be specified in the popup window that appears when the object is created; the higher the number of vertices, the smoother the hollow circular cross-section becomes. Objects that can be created out of tubes include pipes or drinking glasses. (The basic difference between a cylinder and a tube is that the former has closed ends.) Cone A standard cone is made out of n vertices. The number of vertices in the circular base can be specified in the popup window that appears when the object is created; the higher the number of vertices, the smoother the circular base becomes. Objects that can be created out of cones include spikes or pointed hats. Grid A standard grid is made out of n by m vertices. The resolution of the x-axis and y-axis can be specified in the popup window which appears when the object is created; the higher the resolution, the more vertices are created. Example objects that can be created out of grids include landscapes (with the proportional editing tool) and other organic surfaces. Monkey This is a gift from old NaN to the community and is seen as a programmer's joke or "Easter Egg". It creates a monkey's head once you press the Oooh Oooh Oooh button. The Monkey's name is Suzanne and is Blender's mascotte.
EditMode When working with geometric objects in Blender, you can work in two modes: ObjectMode and EditMode. Basically, as seen in the previous section, operations in ObjectMode affect whole objects, and operations in EditMode affect only the geometry of an object, but not its global properties such as the location or rotation. In Blender you switch between these two modes with the TAB key. EditMode only works on one object at a time: the active object. An object outside EditMode is drawn in purple in the 3D Windows (in wireframe mode) when selected; it is black otherwise. The active object is drawn black in EditMode, but each vertex is highlighted in purple (fig. 2). Selected vertices are drawn in yellow (fig. 3) and, if appropriate buttons in the Editing (F9) Context Mesh Tools 1 Panel are pressed (Draw Faces and Draw Edges) also selected edges and faces are highlighted.
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2
Two pyramids, one in EditMode (left) and one in ObjectMode (right).
3
Cube with selected vertices in yellow.
Structures: Vertices, Edges and Faces In basic meshes, everything is built from three basic structures: Vertices, Edges and Faces. (We're not talking about Curves, NURBS, and so forth here.) But there is no need to be disappointed: This simplicity still provides us with a wealth of possibilities that will be the foundation for all our models.
Vertices A vertex is primarily a single point or position in 3D space. It is usually invisible in rendering and in ObjectMode. (Don't mistake the center point of an object for a vertex. It looks similar, but its bigger and you can't select it.) To create a new vertex, change to EditMode, hold do CTRL, and click with the LMB. Of course, as a computer screen is two-dimensional, Blender can't determine all three vertex coordinates from one mouse click, so the new vertex is placed at the depth of the 3D cursor 'into' the screen. Any vertices selected previously are automatically connected to the new one with an edge. Edges An edge always connects two vertices with a straight line. The edges are the 'wires' you see when you look at a mesh in wireframe view. They are usually invisible on the rendered image. They are used to construct faces. Create an edge by selecting two vertices and pressing FKEY. Faces A Face is the most high level structure in a mesh. Faces are used to build the actual surface of the object. They are what you see when you render the mesh. A Face is defined as the area between either three or four vertices, with an Edge on every side. Triangles always work well, because they are always flat and easy to calculate.
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MESH MODELLING.BASIC EDITING
Take care when using four-sided faces, because internally they are simply divided into two triangles each. Four-sided faces only work well if the Face is pretty much flat (all points lie within one imaginary plane) and convex (the angle at no corner is greater than or equal to 180 degrees). This is the case with the faces of a cube, for example. (That's why you can't see any diagonals in its wireframe model, because they would divide each square face into two triangles. While you could build a cube with triangular faces, it would just look more confusing in EditMode.) An area between three or four vertices, outlined by Edges, doesn't have to be a face. If this area does not contain a face, it will simply be transparent or non-existent in the rendered image. To create a face, select three or four suitable vertices and press FKEY.
4
Chopped-off pyramid.
Basic Editing Most simple operations from ObjectMode (like selecting, moving, rotating, and scaling) work identically on vertices as they do on objects. Thus, you can learn how to handle basic EditMode operations very quickly. The only notable difference is a new scaling option, ALT-S which scales the selected vertices along the direction of the normals (shrinksfattens). The truncated pyramid in figure 4, for example, was created with the following steps:
1.
5
Edit Context.
All operations in Edit Mode are ultimately performed on the vertices; the connected edges and faces automatically adapt, as they depend on the vertices' positions. To select an edge, you must select the two endpoints or either place the mouse on the edge and press CTRL-ALT-RMB. To select a face, each corner must be selected.
Add a cube to an empty scene. Enter EditMode.
2.
Make sure all vertices are deselected (purple). Use border select (BKEY) to select the upper four vertices.
Edit Mode operations are many, and most are summarized in the Editing Context Buttons window, accessed via the ( ) button of header or via F9 (fig 5). Note the group of buttons in the Mesh Tools 1 Panel.
3.
Check that the scaling center is set to anything but the 3D cursor (see fig. 1 in Chapter 5), then switch to scale mode (SKEY), reduce the size, and confirm with LMB.
•
Exit EditMode by pressing TAB.
•
4.
One Extra feature for Edit Mode is the Mirroring tool. If you have some vertices selected and you press MKEY you will be presented with a Menu containing nine options. You can select from these to mirror the selected vertice with respect to any of the X,Y or Z axis of the Global, Local, or Viewing reference. One additional feature of EditMode is the CircleSelect mode. It is invoked by pressing BKEY twice instead of only once, as you would for BorderSelect. A light grey circle is drawn around the cursor and any LMB click selects all vertices within. NUM+ and NUM- or the MW, if any, enlarge or shrink the circle.
NSize - Determines the length, in Blender Units, of the normals to the faces,
if they are drawn. Draw Normals - Toggle Normals drawing. If this is ON, face normals are drawn as cyan segments. • Draw Faces - If this is ON, faces are drawn as semi-transparent blue, or as semi-transparent purple if they are selected. If this is OFF, faces are invisible. • Draw Edges - Edges are always drawn black, but if this button is ON, selected edges are drawn in yellow. Edges joining a selected node and an un-selected one have a yellow-black gradient. • All Edges - Only those edges strictly necessary to show the object shape are shown in Object mode. You can force Blender to draw all edges with this button.
Of course all these colors are customizable in the Theme editor.
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MESH MODELLING.UNDO Edit
With WKEY you can call up the "Specials" menu in EditMode (fig. 6). With this menu you can quickly access functions which are frequently required for polygon-modelling.
You can access the entries in a PopupMenu by using the corresponding numberkey. For example, pressing WKEY and then 1KEY you will subdivide the selected vertices without having to touch the mouse at all. 7
•
• •
• •
6
Specials Menu.
• • • • •
•
Subdivide - Each selected edge is split in two,
new vertices are created at middle points, and faces are split too, if necessary. Subdivide Fractal - As above, but new vertices are randomly displaced within a user-defined range. Subdivide Smooth - As above, but new vertices are displaced towards the baricentrum of the connected vertices. Merge - Merges selected vertices into a single one, at the baricentrum position or at the cursor position. Remove Doubles - Merges all of the selected vertices whose relative distance is below a given threshold (0.001 by default). Hide - Hides selected vertices. Reveal - Shows hidden vertices. Select Swap - All selected vertices become unselected and vice-versa. Flip Normals - Change the Normals directions in the selected faces. Smooth - Smooths out a mesh by moving each vertex towards the baricentrum of the linked vertices. Mirror - Same as MKEY described above.
Many of these actions have a button of their own in the Mesh Tools Panel of the Edit Buttons Window (fig. 5). The Remove doubles threshold can be adjusted here, too.
U-Key
Shift-U
Undo and Redo.
Mesh Undo
8
Undo Menu.
As for Blender 2.3 we finally have a true Undo. It works only for Meshes and only in Edit Mode. Mesh undo works in the background saving copies of your mesh in memory as you make changes. Pressing the UKEY in mesh EditMode reverts to previously saved mesh, undoing the freshly performes edit operation (fig. 7). Undo operations are only stored for one mesh at a time. You can leave and re-enter EditMode for the same mesh without losing any undo information, but once another mesh is edited, the undo information for the first is gone. Pressing SHIFT-U re-does the last undo operation (fig. 7). Pressing ALT-U brings up the undo menu (fig. 8). This lists all the undo steps by name so you can quickly find your way back to a known good point in your work. The ALT-U menu also contains the option All Changes. This option is more powerfull than merely pressing UKEY repeadetly, and will reload the mesh data as it was at the beginning of your edit session even if you have used up all your undo steps. Edit undo can be memory intensive. A mesh of 64,000 faces and verts can use over 3Mb of RAM per undo step. In case you are on a machine that is strapped for RAM, there is in the User Preference Window, under Edit Methods, a NumButton for determining the maximum number of undo steps saved. The allowed range is 1-64. The default is 32.
Smoothing As seen in the previous sections, polygons are central to Blender. Most objects in Blender are represented by polygons and truly curved objects are often approximated by polygon meshes.
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MESH MODELLING.SMOOTHING
When rendering images, you may notice that these polygons appear as a series of small, flat faces (fig. 9). Sometimes this is a desirable effect, but usually we want our objects to look nice and smooth. This section shows you how to smooth an object, and how to apply the AutoSmooth filter to quickly and easily combine smooth and faceted polygons in the same object. There are two ways to activate Blender's face smoothing features. The easiest way is to set an entire object as smooth or faceted by selecting a mesh object, in ObjectMode, switching to the Editing Context (F9), and clicking the Set Smooth button in the Link and Materials Panel (fig. 10). The button does not stay pressed, but forces Blender to assign the "smoothing" attribute to each face in the mesh. Now, rendering the image with F12 should produce the image shown in figure 11. Notice that the outline of the object is still strongly faceted. Activating the smoothing features doesn't actually modify the object's geometry; it changes the way the shading is calculated across the surfaces, giving the illusion of a smooth surface.
9
Simple un-smoothed test object.
11
Same object as in fig. 9, this time completely smoothed by 'Set Smooth'.
10
Set Smooth and Set Solid buttons of EditButtons context.
12
Object in editmode with some faces selected.
Click the Set Solid button in the same Panel to revert the shading to that shown in figure 9. Alternatively, you can choose which faces to smooth by entering EditMode for the object with TAB, then selecting the faces and clicking the Set Smooth button (fig. 12). When the mesh is in editmode, only the selected faces will receive the "smoothing" attribute. You can set solid faces (removing the "smoothing" attribute) in the same way: by selecting faces and clicking the Set Solid button. It can be difficult to create certain combinations of smooth and solid faces using the above techniques alone. Though there are workarounds (such as splitting off sets of faces by selecting them and pressing YKEY), there is an easier way to combine smooth and solid faces, by using AutoSmooth. Press the AutoSmooth button in the Mesh Panel of the Edit Buttons (fig. 13) to tell Blender to decide which faces should be smoothed on the basys of the angle between faces (fig. 14). Angles on the model that are sharper than the angle specified in the Degr NumBut will not be smoothed. Higher values will produce more smoothed faces, while the lowest setting will look identical to a mesh that has been set completely solid. Only faces that have been set as smooth will be affected by the AutoSmooth feature. A mesh, or any faces that have been set as solid will not change their shading when AutoSmooth is activated. This allows you extra control over which faces will be smoothed and which ones won't by overriding the decisions made by the AutoSmooth algorithm. 13 AutoSmooth button group in the
EditButtons context.
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14
Same test object with AutoSmooth enabled.
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