# Blender 3D: Noob to Pro/Glossary

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## A

-   **Alpha Channel** is an additional channel in a 2D image for
    transparency. In an image element which stores a color for each
    pixel, an additional value is stored in the alpha channel containing
    a value between 0 and 1. A value of 0 means that the pixel does not
    have any coverage information; i.e. there was no color contribution
    from any geometry because the geometry did not overlap this pixel. A
    value of 1 means that the pixel is fully opaque because the geometry
    completely overlapped the pixel.

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-   **Ambient Light** is light that doesn\'t seem to come from a
    specific source, but is just there. Look under the desk - it\'s
    pretty dark, but there\'s some light there. In the real world, this
    is caused by stray photons bouncing around and occasionally
    ricocheting under the desk. Ambient light is the basic, minimal
    amount of light in the whole scene. Adding too much ambient light
    makes a scene look washed out. Since the light doesn\'t come from
    anywhere, all sides of an object are illuminated equally, and it
    won\'t have any shading on it.

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-   **Ambient Occlusion** (AO) is a ratio of how much ambient light a
    surface point would be likely to receive. It simulates a huge dome
    light surrounding the entire scene. If a surface point is under a
    foot or table, it will end up much darker than the top of someone\'s
    head or the tabletop.

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-   **Armature** is the interconnection of bones that form the skeleton
    of an animated figure. The Inverse Kinematics library contains the
    code to make armatures move. The armature must still be rigged with
    3D objects to give shape to its head, hands, trunk, feet, etc.

## B

-   **Background image**: a 2D image (\"picture\") that is placed
    \"behind\" the entire 3D scene, like a backdrop on a movie set.
    Blender permits the placement of these images in all six directions
    from the origin: back, front, top, bottom, left, right.
-   **Bake**: to precompute computationally-intensive elements of an
    animation. For example, in a physics simulation involving the
    behaviour of fluids or clothing, you would set up the physical
    parameters, then compute (*bake*) the positions and shapes of the
    objects over the duration of the animation. Afterwards, you can
    assign materials and lighting, and then render the frames to produce
    the actual animation. Doing the baking as a separate step, and
    saving the results from that, means you can change your mind about
    the materials and lighting and rerender the frames more quickly.
-   **Bézier surfaces** were first described in 1972 by the French
    engineer Pierre Bézier who used them to design automobile bodies.
    Bézier surfaces can be of any degree, but bicubic Bézier surfaces
    generally provide enough degrees of freedom for most applications.

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-   **BF** is Blender Foundation

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-   **Blend** - *to Blend*, working with Blender; also Blender\'s file
    extension.

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-   **Bounce Light**: Simple lighting situations have a single light,
    called a key light, illuminating one side of an object. This creates
    strong shading and definition of the volume of the object. However,
    a 3D light will often make the contrast too great - the dark side of
    the object is completely black since no light is hitting it. In
    reality it would still be lit a little, just not as much as the
    brightly lit side, because of light bouncing around the room and
    hitting the dark side of the object. In realtime 3D, bounce light is
    not calculated, so you have to create it yourself. Either add a
    little ambient color, or put a second, less bright directional light
    pointing the opposite direction to give a little light to the
    shadows.

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-   **Bump mapping** is a technique where at each pixel, a perturbation
    to the surface normal of the object being rendered is looked up in a
    texture map and applied before the illumination calculation is done.
    Bump Mapping use a gray-scale image map to change the direction of
    surface normals. You can use this to simulate height, so that you
    can paint wrinkles and bumps. 50 % grey means neutral (no change is
    made), lighter means higher, darker means lower. Note that the
    position of faces is not actually changed; by rotating just the
    normals, lighting will change too, to give the illusion of a height
    difference. This has downsides too: the outline of objects isn\'t
    changed, so the trick is given away. For similar effects you can use
    Displacement Mapping and Normal Mapping.

## C

-   **Caustics** in optics is a bundle of light rays. For example a
    caustic effect may be seen when light refracts or reflects through
    some refractive or reflective material, to create a more focused,
    stronger light on the final location. Such amplification, especially
    of sunlight, can burn --- hence the name. A common situation when
    caustics are visible is when some light points on glass. There is a
    shadow behind the glass, but also there is a stronger light spot.
    Nowadays, almost every advanced rendering system supports caustics.
    Some of them even support volumetric caustics. This is accomplished
    by raytracing the possible paths of the light beam through the
    glass, accounting for the refraction, reflection, etc.
-   **CG** is Computer Graphics
-   **CGI** is Computer Generated Imagery

## D

-   **Depth of Field** (DOF) is the
    distance in front of and behind the subject which appears to be in
    focus. For any given lens setting, there is only one distance at
    which a subject is precisely in focus, but focus falls off gradually
    on either side of that distance, so there is a region in which the
    blurring is tolerable. This region is greater behind the point of
    focus than it is in front, as the angle of the light rays change
    more rapidly; they approach being parallel with increasing distance.

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-   **Diffuse Light** is even, directed light coming off a surface. For
    most things, the diffuse light is the main lighting we see. Diffuse
    light comes from a specific direction or location, and creates
    shading. Surfaces facing towards the light source will be brighter,
    while surfaces facing away from the light source will be darker.

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-   **Directional Light** is a light that has a specific direction, but
    no location. It seems to come from an infinitely far away source,
    like the sun. Surfaces facing the light are illuminated more than
    surfaces facing away, but their location doesn\'t matter. A
    Directional Light illuminates all objects in the scene, no matter
    where they are.

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-   **Displacement Mapping** uses a
    greyscale heightmap, like Bump Mapping, but the image is used to
    physically move the vertices of the mesh at render time. This is of
    course only useful if the mesh has large amounts of vertices, but
    the (relatively) new \"Simple Subdiv\" subsurf option allows you to
    add more vertices at render time which will be moved by the
    displacement. This makes it much slower than Bump Mapping, as there
    need to be many more faces to render, but it is much more realistic.

## E

-   **Environment Maps** (EnvMaps) is the method of calculating
    reflections. Involved rendering images at strategic positions and
    applying them as textures to the mirror. Now in most cases obsoleted
    by Raytracing, which though slower is easier to use and more
    accurate.

## F

-   **Focal Length** of a lens is the
    distance along the optical axis from the lens to the focus (or focal
    point). The inverse of a lens\' focal length is called its power.

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-   **Focus "wikilink")** of a lens is the point onto
    which collimated light parallel to the axis is focused.

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-   **Foreshortening**

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-   **Fresnel** lens is a type of
    lens invented by Augustin-Jean Fresnel. Originally developed for
    lighthouses, the design enables the construction of lenses of large
    size and short focal length without the weight and volume of
    material which would be required in a lens of conventional design.
    As it relates to rendering, fresnel refers to the tendency of
    materials to be more reflective when light strikes at a high angle
    of incidence\-- think of how sunlight reflects from distant water,
    but penetrates closer water, or of how road glare is most extreme at
    dawn or dusk. This varies with material, and specification of
    fresnel is an important part of material definition.

## G

-   **GE** is Game Engine.

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-   **Global Illumination** (GI) is
    a superset of radiosity and ray tracing. The goal is to compute all
    possible light interactions in a given scene, and thus obtain a
    truly photorealistic image. All combinations of diffuse and specular
    reflections and transmissions must be accounted for. Effects such as
    colour bleeding and caustics must be included in a global
    illumination simulation.

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-   **Gouraud shading** is a method used
    in computer graphics to simulate the differing effects of light and
    colour across the surface of an object. In practice, Gouraud shading
    is used to achieve smooth lighting on low-polygon surfaces without
    the heavy computational requirements of calculating lighting for
    each pixel. The technique was first presented by Henri Gouraud in
    1971.

## H

-   **High Dynamic Range
    Image** (HDRI) is a set of
    techniques that allow a far greater dynamic range of exposures than
    normal digital imaging techniques. The intention is to accurately
    represent the wide range of intensity levels found in real scenes,
    ranging from direct sunlight to the deepest shadows. The use of high
    dynamic range imaging in computer graphics has been popularised by
    the work of Paul Debevec. Blender uses Yafray for these techniques.

## I

-   **Index Of Refraction** (IOR) is
    about the way that light passes through different types of
    materials\... diamond, glass, water etc. When a light ray travels
    through the same volume it follows a straight path. However if it
    passes from one transparent volume to another, it bends. This is why
    a straw in water looks bent. The amount of bending differs between
    materials. The angle by which the ray is bent can be determined by
    knowing two things: the angle at which the incoming ray has been
    cast and the Index of Refraction. This IOR value is unique for every
    material. Glass has an IOR of about 1.5 and water 1.3. By increasing
    the IOR value for a Blender material, you can control how much the
    environment behind the transparent object is distorted, and thus
    improving the realism of the shader.

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-   **Interpolation** (IPO) is an
    animation curve: it indicates how the object must \"move\" between
    an initial and a final position, at the rate determined by the
    rendering engine. Objects can be animated in many ways. They can be
    animated as Objects, changing their position, orientation or size in
    time; they can be animated by deforming them; that is animating
    their vertices or control points; or they can be animated via very
    complex and flexible interaction with a special kind of object: the
    Armature.

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-   **Inverse Kinematics** (IK) is
    the process of determining the movement of interconnected segments
    of a body or model, starting from the desired motion of the
    endpoints of the armature. Using ordinary Kinematics on a
    hierarchically structured object you can for example move the
    shoulder of a puppet. The upper and lower arm and hand will
    automatically follow that movement. IK will allow you to move the
    hand and let the lower and upper arm go along with the movement.
    Without IK the hand would come off the model and would move
    independently in space. The Blender Armature System includes Inverse
    Kinematics. For general armatures there are many possible solutions
    to the IK.

## J

-   **JPEG** Acronym for Joint Photographic Expert
    Group (pronounced jay-peg) is a commonly used standard method of
    lossy compression for photographic images. The file format which
    employs this compression is commonly also called JPEG; the most
    common file extensions for this format are .jpeg, .jfif, .jpg, .JPG,
    or .JPE although .jpg is the most common on all platforms.

## K

-   **Keyframe** is a frame in an animated sequence of frames that was
    drawn or otherwise constructed directly by the user. When all frames
    were drawn by animators, the senior artist would draw these frames,
    leaving the \"in between\" frames to an apprentice. Now, the
    animator creates only the first and last frames of a simple
    sequence; the computer fills in the gap. This is called tweening.

## L

-   **Luminosity** (more properly called
    luminance) is the density of luminous intensity in a given
    direction. In astronomy, luminosity is the amount of energy a body
    radiates per unit time. It is typically expressed in the SI units
    watts, in the cgs units ergs per second, or in terms of solar
    luminosities, Ls; that is, how many times more energy the object
    radiates than the Sun, whose luminosity is 3.827×1026 W.

## M

-   **Motion Blur** is the simulation of the
    phenomenon that occurs when we perceive a rapidly moving object. The
    object appears to be blurred because of our persistence of vision.
    Doing motion blur makes computer animation appear more realistic. It
    can be thought of as adding back some of the time dependence
    expressed in the Rendering Equation.

## N

-   **Nabla**. *Ton wrote:* Almost all procedural
    textures in Blender use derivatives for calculating normals for
    texture mapping (with as exception \"Blend\" and \"Magic). The
    texture normal, the derivative, is calculated by using four samples
    in the texture formula:

`s0= texture(x, y, z)`\
`s1= texture(x+nabla, y, z)`\
`s2= texture(x, y+nabla, z)`\
`s3= texture(x, y, z+nabla)`

`normal[0]= s0-s1`\
`normal[1]= s0-s2`\
`normal[2]= s0-s3 `

Up to now, the \"nabla\" offset was a constant (0.025) which worked fine
in most cases, but doesn\'t give proper control over the way a texture
is sampled, for example to make the effect smoother or sharper. This
feature especially is useful in combination with the ColorBand feature.

-   **Non-Linear Animation** (NLA) allows the animator to edit motions
    as a whole, not just the individual keys. Nonlinear animation is not
    just about editing and manipulating groups of keyframes, but it also
    allows you to combine, mix, and blend motions to create entirely new
    animations.

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-   **Nonuniform Rational
    B-Splines** (NURBS) is a
    computer graphics technique for generating and representing curves
    and surfaces.

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-   **Normal** (Surface Normal) to a flat surface is a three-dimensional
    vector which is perpendicular to that surface. A normal to a
    non-flat surface at a point p on the surface is a vector which is
    perpendicular to the tangent plane to that surface at p.

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-   **Normal Mapping** is similar to Bump Mapping, but instead of the
    image being a greyscale heightmap, the colours define in which
    direction the normal should be shifted, the 3 colour channels being
    mapped to the 3 directions X, Y and Z. This allows more detail and
    control over the effect.

## O

-   **Orange** is the first Blender open
    movie project.

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-   **Oversampling** (OSA), also called **Anti-Aliasing** is the
    technique of minimizing aliasing when representing a high-resolution
    signal at a lower resolution. In most cases, anti-aliasing means
    removing data at too high a frequency to represent. When such data
    is left in a signal, it causes unpredictable artifacts.

## P

-   **Phong** shading term is used indiscriminately to describe both an
    illumination model and an interpolation method in 3D computer
    graphics. Phong reflection is a local illumination model and can
    produce a certain degree of realism in three-dimensional objects by
    combining three elements - diffuse, specular and ambient for each
    considered point on a surface. It has several assumptions - all
    lights are points, only surface geometry is considered, only local
    modelling of diffuse and specular, specular colour is the same as
    light colour, ambient is a global constant.

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-   **Point Light** is a light that has a specific location and radiates
    equally out in all directions. Examples of point lights would be
    candles or bare lightbulbs. Surfaces close to the point light are
    brighter than those which are far away. Point lights have
    attenuation, which controls how quickly the light intensity drops
    off as you move away from it. Lights with high attenuation are very
    localized, while lights with low attenuation will spread farther.

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-   **Polygonization** *(of meta-surfaces)* is the process of
    approximating the meta-surface via polygons so it can be
    displayed/rendered in Blender.

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-   **Purple** runs as a normal Verse client. It implements a node
    database to mirror the contents of its host. It loads the plug-ins,
    which reside in libraries, from local disk as DLLs or shared objects
    depending on the platform.

## Q

-   **Quaternion** is a representation of 3D
    rotations with four numbers. It can be interpreted as an extension
    of complex numbers to 3D. The interpretation of the four numbers is
    not very intuitive for a human, but the numerical advantage of
    quaternions is that it is the smallest mathematical representation
    that does not suffer from the gimbal
    lock
    singularity problem. This
    problem occurs for example with Euler
    angle representations, when a small
    change in the 3D orientation can give rise to a large change in
    Euler angles.

## R

-   **Radiosity** is a more accurate but also more process-intensive
    technique than raytracing, that calculates patterns of light and
    shadow for rendering graphics images from three-dimensional models.
    One of the many different tools which can simulate diffuse lighting
    in Blender.

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-   **Raytracing** works by tracing the path taken by a ray of light
    through the scene, and calculating reflection, refraction, or
    absorption of the ray whenever it intersects an object in the world.
    More accurate than Scanline, but much slower.

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-   **Render**: to generate actual viewable images from a 3D model or
    scene. This may or may not need to happen in real time; for example
    an interactive game requires real-time rendering, whereas a feature
    film does not. These situations require very different rendering
    techniques.

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-   **Refraction** in geometric optics is the change in direction of a
    wave due to a change in velocity. It happens when waves travel from
    a medium with a given refractive index to a medium with another. At
    the boundary between the media the wave changes direction; its
    wavelength increases or decreases but frequency remains constant.
    For example, a light ray will refract as it enters and leaves glass.

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-   **Relative Vertex Keys** (RVK) are part of a keyframe animation
    system that operates on vertex level objects. Each (shape) key is
    stored as a morph target such that several keys may be blended
    together to achieve complex mesh animation. With RVK you can create
    facial expressions, speech, and other detailed animated keyframed
    movements within your mesh-based models.

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-   **Rig:** the controls that aid in the manipulation of a digital
    character.

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-   **Rigging** is the process by which a person creates constraints and
    relationships between objects that will generate controls to aid in
    the manipulation of a digital character.

## S

-   **Scanline** is one row of pixels in the final render. Also the term
    for one of the methods of rendering which Blender can use. It is
    much faster than Raytracing, but allows fewer effects, such as
    reflections, refractions, motion blur and focal blur.

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-   **Seed**: a starting number for generating a random-looking number
    sequence. Using the same seed will always give you the same
    sequence. Technically, such a sequence is not truly random, it is
    only *pseudorandom*.

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-   **Shader**: an algorithm for computing the appearance of a given
    material based on the colour, angle and intensity of the light.
    *Specular* shaders produce a more shiny, mirrorlike finish, while
    *diffuse* shaders give a duller surface appearance. There are also
    *toon* shaders, which are deliberately designed to produce an effect
    more akin to a cartoon drawing, with delineated object borders and
    less gradation of colours over a surface.

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-   **Shadows**: simulated lights don\'t normally cast shadows. And,
    they also pass through solid objects - so a light inside a closed
    box would actually illuminate things outside the box as if the box
    were transparent. The shading on objects is only calculated based on
    the angle of the surface.

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-   **Specular Light** refers to the highlights on reflective objects,
    like diamonds, billiard balls, and eyes. Specular highlights often
    appear as bright spots on a surface, at a point where the light
    source hits it directly. Ambient, Diffuse, and Specular are called
    the three components of a light source. Each one is given a color,
    which, when added together, create the final color of a light. For
    most lights, the main overall color of the light is defined by the
    Diffuse color. Sunlight or lightbulbs would be white, while
    moonlight would be a darker blue, and a candle would be yellow. You
    can use the ambient color to adjust the overall color range of the
    light source; or, you can get a slight tint to shadows by making the
    diffuse component yellow and the ambient a slight blue. In many
    lights, the ambient color is left at black, meaning that it won\'t
    have any effect. Specular components are often left at white, but
    you can make them different colors to get interesting effects. Most
    of the time you can completely ignore the specular and diffuse
    settings on a light, but just be aware that the way you set the
    color is by specifically setting the diffuse color. The final color
    that an object appears to be is a combination of the light hitting
    it and the color of the surface.

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-   **Spotlight** is a light with both location and direction. A
    spotlight sends out a cone of light defined by the spotlight angle,
    and illuminates only objects within that cone. Spotlights also have
    attenuation, as well as a parameter that controls whether the spot
    of light is sharply defined or has smooth edges. These 4 types of
    lights are listed in order of computational complexity; the more
    lights you have, the more work the computer has to do. Generally
    it\'s a good idea to use directional lights whenever possible, since
    they\'re the cheapest, and use pointlights and spotlights sparingly.

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-   **Stucci** is one of the classes of blender textures. *Stucci* is
    not an English word, but is used in Blender as the plural of
    stucco.

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-   **Subdivision Surface** (Subsurf) is the tool which subdivides your
    model at render-time, without affecting your mesh at design-time.
    There are two subsurf algorithms in Blender to choose from - *Simple
    Subdiv*, which doesn\'t affect the shape of your mesh, and is used
    to add detail to displacement mapping or render-time radiosity, both
    of which operate on a per-vertex basis. The other is
    *Catmull-Clark*, a common subdivision algorithm which smooths out
    curves, and allows you to make complicated smooth surfaces (e.g.
    people, plants, etc.) with very few faces. However this algorithm
    can sometimes (read: often) have strange results with meshes
    containing triangles or vertices with many edges (\"poles\"), unless
    it is correctly handled.

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-   **Sub Surface Scattering** (SSS) is a mechanism of light transport
    in which light penetrates the surface of a translucent object, is
    scattered by interacting with the material, and exits the surface at
    a different point. All non-metallic materials are translucent to
    some degree. In particular, materials such as marble, skin, and milk
    are extremely difficult to simulate realistically without taking
    subsurface scattering into account.

## T

-   **Tuhopuu** is an experimental version of Blender that is like a
    code playground, developers can put their new code in there to be
    tested and played with by users before it gets put into the official
    Blender. Tuhopuu is Finnish for \"Tree of destruction\".

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-   **Tweening** is short for in-betweening, the process of generating
    intermediate frames between two images to give the appearance that
    the first image evolves smoothly into the second image. Tweening is
    a key process in all types of animation, including computer
    animation. Sophisticated animation software enables one to identify
    specific objects in an image and define how they should move and
    change during the tweening process. Another word for tweening is
    interpolation.

## U

-   **UV Mapping** (UV) This refers to the process of re-parameterizing
    a 3d object with dimensions x, y and z into a 2d plane with
    coordinates u and v. Most texturing requires this step because it
    tells the program HOW to apply a 2d image map onto a 3d object. If
    all your textures must be 2d and flat, the easiest way to determine
    what pixel goes where is if your model is flattened and made 2d. It
    also establishes a relationship between a 2d image and the mesh such
    that if the mesh deforms, the image map will deform along with it.
    Think of it as skinning a cat and pinning its hide onto cardboard to
    facilitate painting it!

## V

-   **Verse** is a network protocol that lets multiple applications act
    together as one large application by sharing data over a network. If
    one application makes a change to shared data, the change is
    distributed instantly to all the other interested clients.

## W

-   **WC** is Weekend Challenge.

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-   **WIP** is Work In Progress.

## X

## Y

-   **Yet Another Free Raytracer** (YafRay) is an open source ray
    tracing program that uses an XML scene description language. It has
    been integrated into, and is often used to render scenes made in,
    Blender.

## Z

