CPSC 424, Spring 2010
Lab 4: Introduction to Blender

BLENDER is a three-dimensional modeling and rendering program. This means that you can use it interactively to construct 3D "worlds" and you can render images of the worlds you create. Blender uses OpenGL for rendering. It also uses OpenGL for drawing its user interface. The interface has to be called unusual. You should not expect to be able to start up Blender and figure out what to do with it! However, the interface is fairly usable once you get experienced with to it.

Blender can make animations, but we won't be doing anything with animation in this lab. It can also be used to create simple interactive games. However, we won't be doing anything interactive with Blender games in this course. In general, there are many, many parts of the interface whose function you won't understand (and in many cases, I don't understand them either).

The main Blender web site is www.blender.org. You can find information on the program and on the Blender user community at this site, and there is a variety of tutorials. An html copy of the Blender 2.3 Guide -- somewhat outdated -- is at http://www.blender.org/documentation/htmlI/. However this lab sheet should contain all the information that you need to get started.

Running Blender

Blender is installed on the computers in the lab. The Blender interface uses the numerical keypad, so I suggest that you choose a computer that has a full-size keyboard. You can find Blender in the "Graphics" section of the application menu. You can start it in either Full Screen or Windowed mode. If you use Gnome, you must turn off "Visual Effects" (under "Preferences" / "Appearance", in the "Visual Effects" tab); otherwise the effects will interfere with Blender and make it unusable.

When Blender starts, the majority of the screen is filled with a "3D View" that gives a view of a three-dimensional world. Below the 3D View window is a Buttons Window, which will be discussed below. A 3D scene in Blender can contain objects, lights, and cameras. The view in the 3D Window also contains a grid and a "3D cursor." These are not part of the world, just part of the user interface. The picture at the right shows part of the world after some modifications. At the top right is an object, an "icosphere". It is outlined in pink, and it has its own set of axes because it is the current selection. At the bottom is a camera. The view has been rotated to show that the camera appears as a pyramid with an arrow to show which direction is the top of the camera. When you render an image, the image shows the view from this camera. The small item at the top left is a lamp, which can provide lighting for the scene. The 3D cursor is the other object, on the right side of the image.

Changing the View

The 3D View window shows you a two-dimensional projection of a three-dimensional world. You need to be able to change the view, to look at the world from a different viewpoint. This can be done using the mouse or using the keys on the numeric keypad. (The keypad is the group of keys on the right of the keyboard.) This table tells you how. Keyboard commands are sent to the currently selected window. To make sure they are sent to the 3D View window, click on that window.

Changing the View with the Mouse
Drag with middle mouse button -- Rotate the view. (A rotated view might look cool, but it's not necessarily best for modeling.)
Hold down Shift, and drag with middle mouse button -- Translate the view (up, down, left, right).
Hold down Control, and drag with middle mouse button -- Zoom the view. Move mouse up to zoom in, down to zoom out. You can also zoom in and out with th scroll-wheel feature of the mouse. (This is very annoying on the iMacs in the lab when you are trying to use the middle button for some other reason.)
Changing the View with the Keypad
Keypad 0 View from the camera. Hit 0 again to return to the regular view.
Keypad 7 Default view (from "above")
Keypad 1 View from "front"
Keypad 3 View from "side"
Keypad 2,4,6,8 Rotate the view.
Keypad +,- Zoom in and out.
Keypad 5 Switches between "orthogonal" and "perspective" projection. (Orthogonal, the default, is generally best for modeling, but perspective is closer to what to you would actually see.)

Adding, Selecting, and Deleting Objects

Changing the view does not modify the contents of the world. To do that, you have to add objects to the world. This is where the 3D cursor comes in. A newly added object is always added to the world at the position of the 3D cursor. You have to position the 3D cursor before adding the object. The 3D cursor is positioned by clicking, with the left mouse button, on the world window. The 3D cursor is positioned in three-dimensional space. You can't tell where it is by looking at the world from one point of view. Typically, you would check the position of the 3D cursor from several viewpoints by using the Keypad 1, 3, and 7 keys to switch between viewpoints.

The ADD menu Once you have the 3D cursor in position, use the "Add" menu to add an object to the world. Click on "Add" in the menu bar, then click on "Mesh" in the menu. This gives a sub-menu containing various mesh objects. ("Mesh" just means that it's made up of polygons.) Stick to mesh objects for now. The picture at the right shows the "Add" menu being used to add a "UVsphere." A UVsphere is a sphere divided by lines of latitude and longitude. An ICOsphere is divided into triangles. A Plane is actually just a rectangle. (When you first start Blender, the default world that you see contains a Mesh Cube as its only object.)

When adding certain types of objects, you will have to select a few options. The image at the left shows the little dialog box that shows up when you use the Add/Mesh/Cylinder command. For a Cylinder, you have to specify the number of Vertices, the Radius, the Depth (that is, height), and whether or not you want to "Cap Ends". To accept the default values, just press return or click OK. The buttons for numerical input are examples of Blender's funny input buttons. I'll tell you later how to change the value on such a button. The "Cap Ends" button is for entering a boolean value. In the picture, the option is on. If you turn the Cap Ends option off, you get a hollow tube with no top and bottom.

Objects can be selected. When you apply an edit operation to the 3D View window, it affects the selected object or objects. In Blender, you select an object by right-clicking it. Selected objects are shown outlined in pink. You can select multiple objects by holding down the Shift key as you right-click the objects. When you do this, the little set of red/green/blue axes move to the center of the group of objects -- and if you transform the group as a whole, the transform is relative to this center. When multiple objects are selected, certain operations only apply to the most recently selected object. This object is shown in a slightly brighter pink.

To delete selected objects, just hit the X key or the Delete key. You will be asked to confirm the deletion. You can delete the entire world, and return to the default world, with Control-X. For these and all keyboard commands, the command is sent to the selected window. You can make sure that the 3d View Window is selected by left-clicking it.

As you modify the world, you can undo most operations by pressing Control-Z, including adding and deleting objects. (Unfortunately, Control-X doesn't seem to be undoable.)

(By the way, you can pop up a menu containing most of the menu commands by hitting the space bar. This positions the pop-up menu at the current mouse position, so it saves you the trouble of moving the mouse up to the menu bar. You'll find that there are lots of such keyboard shortcuts in Blender)

Numerical Input Buttons

Blender uses some unusual buttons for numerical input, like the one shown above for inputting the number of vertices of a cylinder. These are actually pretty nice. They work like this:

Transforming Objects

You can translate objects (that is, move them around), you can scale objects (this is, change their sizes), and you can rotate objects. This is an essential part of modeling. To apply one of these operations to the selected object(s), use a combination of keyboard and mouse. Note that you do not simply click-and-drag an object to move it.

Translation Press the "G" key. (G stands for "grab".) Move the mouse without holding down any button. You can move the object in the plane of the screen only. Click with the left mouse button to finish. Click with the right mouse button to abort. (Hitting return will also finish; hitting Escape will also abort.) After hitting the "G" key, you can hit "X", "Y" or "Z" to constrain motion to one axis. Alternatively, you can start moving an object if you just right-click and start dragging. However, releasing the right-mouse does not end the move! You still have to end it as described above. There is even a third way to start a move, with a "gesture": Click the left mouse button and drag it a short distance in a straight line anywhere on the 3D View Window. The selected object -- wherever it is -- is the one that will be dragged. The move operation begins when you release the left mouse button.
Scaling Press the "S" key. Move the mouse towards or away from the object to change its size. The size changes in all three dimensions. Click with the left mouse button to finish. Click with the right mouse button to abort. After hitting "S", you can hit "X", "Y", or "Z" to scale the object in the direction of one axis only.
Rotation Press the "R" key. Move the mouse to rotate the object around a line perpendicular to the screen. Click with the left mouse button to finish. Click with the right mouse button to abort. If you hit "R" a second time, you can freely rotate the object. After hitting "R", you can hit "X", "Y", or "Z" to rotate the object about the specified axis. The default is to rotate the object about a line perpendicular to the screen. To start a rotation operation with a gesture, click the left mouse button and drag it in a circular arc anywhere on the 3D View Window. The rotation operation starts when you release the mouse.

Whether rotating, scaling, or translating, you can hold the Control key down to limit the changes, such as to integral amounts while translating or to multiples of ten degrees while rotating. Also, you can use the arrow keys to make small adjustments.

It is also possible to input translation, scaling, and rotation factors numerically. To do this, hit the "N" key. ("N" stands for numeric input.) This pops up an input box with numeric buttons where you can set the values for the selected object.

All these operations can be applied to the camera, just as they are applied to any other object. You can move and point the camera to get the view of the world that you want to see when you render an image of your world.

Note that rotations and scaling are relative to the "center" o the object, which is shown as a tiny yellow or pink ball, with a small white circle drawn around it. This center point is not necessarily at the geometric center of the object.

You can get yourself real confused if you don't remember to press the left or right mouse button to end a transformation operation.

Understanding Edit Mode

When an object is first added to the world, it is in "Edit Mode." You can put the selected object into Edit Mode or exit from Edit Mode by pressing the TAB key.

Funny cylinder In Edit Mode, the vertices of a mesh object are marked by tiny pink or yellow balls. Edit Mode is for editing the individual vertices of the object. In Edit Mode, you can select one vertex or a group of vertices. Selected vertices are shown in yellow, unselected vertices in pink. You can apply transformations to an individual vertex or a selected group of vertices, just as if they were objects. When you scale or rotate a group of vertices, only the vertices in the group are scaled or rotated. The object at right, for example, was made from a 6-vertex cylinder by selecting the vertices at the top of cylinder and rotating them.

When you first enter Edit Mode for a mesh object, all of its vertices are selected. Pressing the "A" key will deselect all vertices. If you press the "A" key when no vertices are selected, all the vertices will be selected.) You can select a vertex by right-clicking. Hold down the shift key while right-clicking to select multiple vertices. There is a way to add a group of vertices to the selection. Hit the "B" key. You can then draw a "box" by left-clicking and dragging with the mouse. Vertices within the box are added to the set of selected vertices. This is an easy way, for example, to select all the vertices at the top of cylinder. You might have to change the point of view several times while selecting the vertices and performing operations on them.

There are a lot of things you can't do in Edit Mode, so don't forget that you have to press the TAB key to get out of Edit Mode.

By the way, the "A" and "B" keys can also be used outside of Edit Mode for selecting sets of objects.

Rendering an Image

Once you have constructed a scene, you can see a rendered image by pressing the F12 key, or by using the "Render Current Frame" command from the "Render" menu. The scene needs to be lit. There is one light in the default setup.

When you render a scene, a new windows opens to show the rendered image. You can press Escape to dismiss the window, or just click back onto the Blender window.

The objects in the world will be an ugly gray unless you have applied materials to the objects. This is covered below.

The rendered image shows the world from the camera's viewpoint. Remember that you can get a preview of this view by pressing the Keypad-0 key. You can edit objects as usual in the Keypad-0 view, which can make it easier to arrange the objects in the image. Futhermore, you can even select the camera and transform it while the camera view is selected!

Saving a File or an Image

Working with files is my least favorite part of Blender, but you have to know how to do it if you want to save your work. The "Save" and "Save As" commands in the "File" menu are used to save complete Blender projects. This allows you to come back later, open the file, and continue work on the same project.

file saving When you save or open a file, the World Window changes into a File Browser window. There are two lines at the top of the window that show the directory where the file is to be saved and the name that is to be given to the file. You can enter these by clicking and typing. Press return to finish typing a line. The image shows the directory and file names, just after I have typed the file name, before pressing return. To actually create the file, you have to press return again, or click the "Save File" button at the top-right of the window.

You can also select the directory by browsing the list of files. Similarly for the file name, if you are opening a file or if you are saving and want to replace an existing file.

To save an image that you have rendered, use the "Save Rendered Image" command from the "File" menu. The default is to save the image in JPEG format, but the format can be changed. The proper file extension will be added to the name that you provide, if you don't include it. Before rendering the image, you can set the image size and format as well as other rendering options. To do this, you need to use the Scene Buttons. Press F10 to show the Scene Buttons in the Buttons Window at the bottom of the Blender interface. (Or click the small "Scene" button at the top of the Buttons window.) Here is some of what you should see:

The button labeled "Image Format" sets the format of saved images. Jpeg and Png are the only really likely options. The numeric buttons labeled "Image Size" are used to set the size of the rendered image. Clicking the Render button is equivalent to hitting F12. The OSA button is a toggle button that can be either on or off. Here, it has been set to on. Turning OSA on enables full-screen antialiasing, which will increase the quality of the image, at the expense of a little more rendering time. Other buttons in this picture control various settings for rendering and animation.

Adding a Material to an Object

The default color of an object is gray. To change this, you have to add a "material" to the object. This is done using the material buttons of the Button Window. First, you need to know more about accessing different types of buttons. A large part of Blender's functionality is contained in the Buttons Window, which can show many different panels of buttons. To select a particular panel of buttons, you can use the panel selection buttons at the top of the Buttons window:

The six buttons on the left in this picture are always present. They choose the general focus of the buttons. To work with materials and other things that affect the appearance of objects, you want to select the Shading Buttons. (We'll use the Editing Buttons later.)

The five buttons to the right are present when the Shading Buttons are selected. Use these buttons to select the type of properties that you want to edit. We start with the Material Buttons, which are selected in the picture. You can just hit F5 to get to the material buttons directly.

When you select the Material Buttons, you see the material properties for the object that is selected in the 3D View window, and you can assign a material to that object or edit its material.

If the object does not already have a material, you won't see much besides the "Add New" button, as shown at the right. Click this button to add a material to the object. (You can also click the pop-up-menu button on the left end of the "Add New" button to see a list of materials that have already been defined. You can choose to add one of them to the object. In that case, you can have several objects that all use the same material.)

Once an object has a material, there will be lots of buttons in the Button Window that are used to edit the material. For now, look for the R, G, and B sliders near the left of center. These can be used to change the color of the material.

Adding a Texture to an Object

A "texture" makes the color of an object vary from point to point. The colors could be copied from an image, effectively painting the image on the surface of the object. This is called an "image texture." Alternatively, the color can be computed algorithmically from the coordinates of the point. This is called a "procedural texture."

In Blender, a texture is part of a material. You can't add a texture to an object unless you have already added a material, as described above. (The default gray material that you see on a newly created object does not count.)

To add a texture to an object, select the object. Then select the Edit Texture Properties button (as shown in the above illustration; or you can simply press F6). If the object already has a texture, you will be able to edit it. Otherwise, use the "Add New" button. Once you've added the texture, a "Texture Type" button will appear where you can choose the type of texture that you want to use. And once you select the texture type, a whole new set of buttons will appear for editing the texture.

One type of texture is an Image texture. If you choose that type, you will see a "Load" button that you can click to select the image that you want to use as a texture.

The remaining texture types are procedural textures. I suggest trying "Marble", "Clouds", and "Wood". When you select one of these, the new buttons that appear allow you to modify the appearance of the texture. The Marble pattern, for example, usually looks better if it's set to "Sharp" or "Shaper" rather than "Soft."

The Clouds, Wood, and Marble textures make patterns of two colors. The funny thing is that both colors are set using the Material Buttons, not the Texture buttons. The Texture Buttons set the pattern that the colors make, but not the colors themselves. So, to adjust the colors, go back to the Material Buttons by clicking the button to edit material properties (or pressing F5). One of the colors for the texture is the basic material color, as set by the RGB sliders in the center of the Material Buttons. To find the other set of RGB sliders, you will have to find the "Map to" tab, all the way to the right (and probably not selected by default). The default second color is an ugly magenta, so you probably want to change it.

Adding a Light

There is already one light in the default scene, which you can drag around so that it best illuminates your objects. You can also add additional lights, using the "Lamp" command in the "Add" menu. The lamp appears at the position of the 3D cursor. You might have to add several lamps to properly light your scene.

By default, a light acts like a point source of light. There are several other types of light, including a "sun", which shines from a given direction, and a "spot", which is a spotlight. To edit a light, make sure that the "Shading Buttons" are selected, and that the light is the selected object in the 3D View window. Besides changing the type of light, you can increase or decrease the lamp's brightness (called its "intensity"). You can change the color of the light. And you can change other properties such as the beam angle of a spotlight.

World Buttons

In addition to the objects in the world, you can set certain global properties of the entire world. The image shown above, of a twisted six-sided cylinder, has "stars" and a "sky" that fades from dark blue to black. These properties are set using the World Buttons. To see the World Buttons, Make sure that the Shading Buttons are selected, and click the small icon for editing world properties.

You will see RGB sliders for setting the horizon ("Ho") and zenith ("Ze") colors. These control the color of the bottom of the sky and of the top of the sky, but you wont see the sky gradient effect unless you also turn on the "Blend" option (next to the preview image).

You can get stars simply by clicking the Stars button to turn that option on, in the middle section of the World Buttons.

Finally, Facets

Mesh objects have a faceted appearance that is OK in some cases, but not necessarily appropriate for all objects. For example, you would probably like your spheres to be smooth rather than faceted.

To give a mesh object a smooth appearance, go to the Edit Buttons. (You can simply hit F9.) Select the object you want to make smooth. Then click the "Set Smooth" button in the Button Window (at the bottom, near the left end). You can undo the effect by clicking the "Set Solid" button.


These exercises are due next Tuesday, February 23. They should be posted on your web site, along with short comments (as usual). You should also save copies of the .blend files from your projects, and turn them into the homework folder in a folder named lab4.

Exercise 1: The file named stage.blend contains a Blender project. You can find a copy in /classes/s10/cs424. You should be able to open it by double-clicking or by using the Open command in Blender. The scene in this project shows several objects on a stage, with a spotlight and shadows. The stage is made from two Plane objects, scaled and rotated into place. The objects and stage are the default grey color. Add color or texture to each object and to the Planes that make up the stage. Add a sphere and at least one more object -- maybe something hanging on the well -- to the scene. Try to make it attractive. Here's what it looks like at the start:

Exercise 2: Make an object similar to my twisted six-sided cylinder, and show it nicely displayed in a well-lighted world with stars. Use different textures and colors, but make a twisted six-sided cylinder. Here's my image again (but I've cheated by setting up a yellowish spotlight with "halo" effect turned on -- the halo makes the yellow glow):

Exercise 3: Use Blender to make an image of a snowman -- with a top hat. (It would be nice if the snowman is standing on a textured plane.)

Exercise 4: Use Blender to make an additional image of your choice that you believe will impress me with the amount of effort that you have put into it.

David Eck