Visualization Glossary

In an animation sequence, an element(s) that are scripted to move or rotate in a controlled manner. Created as a cell.

Process within radiosity solving that dynamically subdivides a surface element mesh along shadow boundaries, resulting in more accurate and detailed shading.

Source of several common computer graphics artifacts such as jagged lines, missing objects, and jerky motion in animation. In signal processing terms, aliasing is caused by the under-sampling of a signal, resulting in some high-frequency components of the signal assuming the alias (or false identity) of the low frequency components, and mixing together in such a way that they can no longer be distinguished properly.

Imaginary light that is presumed to strike every point on a surface with equal intensity. Used to approximate the large-scale effects of diffuse inter-reflections, a phenomenon not usually accounted for by most lighting methods. Ambient light should be turned off when using particle tracing or radiosity solving, both of which take into account the diffuse reflection of light between surfaces.

Actor that is scripted to designate a viewing position, orientation, and perspective for animation.

File (“.asf”) that contains design and rendering settings while recording an animation sequence. Particularly useful for collaborative recording of animation scripts on networked systems or continuing disrupted recordings.

Special rendering processing to remove or limit the appearance of aliasing artifacts in an image or an animation sequence. See also sample.

Light source created from a MicroStation shape element. This type of light source casts softer, more natural shadows than a Point light source.

Imaginary entity that specifies a scene's viewing position, orientation, and perspective. Also, see animation camera.

Lighting effects caused by light reflected off surfaces, or refracted through transparent objects.

Shading effect observable in particle traced and radiosity solutions caused by diffuse-inter-reflections between surfaces. For example, a colored wall often reflects a small amount of its color onto an adjoining white wall.

A global process of light transport among all the surfaces in an environment, based on a series of diffuse reflections between surfaces. This is the process that is simulated in radiosity solving.

Type of reflection that sends light in all directions with equal energy. Diffuse reflection is said to be “view-independent.” See also specular reflection.

To move the view cone while keeping the camera and target points in the same positions relative to each other — that is, without changing its orientation.

To move a directional light source and its target point such that they remain in the same positions relative to each other — that is, without changing its orientation.

For radiosity solving, a triangular subdivision of a patch. Light energy is “shot” from a single patch to each of the elements of the other surfaces.

For radiosity solving, the set of elements composing a surface.

To move the view cone, linearly, in a vertical direction.

Imaginary cube surrounding the entire design, on which images are applied as environment maps.

Image file representing the projection of a 3D environment onto a 2D surface from a specific point of view. A set of these files can be applied to the six faces of the environment cube that surrounds a design (or environment). An environment map is not directly visible in the view, but is seen only when reflected or transmitted by surfaces in the model to which material characteristics are applied.

Animation script recording technique that results in frames that consist of two fields each (one for the even-numbered scan lines and one for the odd-numbered scan lines). Used to improve playback on NTSC and PAL video display systems that employ interlaced display.

Single rendered image that is part of a series of rendered images that make up an animation sequence.

Identifies a frame's relative position in an animation sequence. Since the speed of an animation sequence (expressed in frames per second) is constant throughout the animation, frame numbers can also be thought of as points in time. Therefore, fractional frame numbers can be specified in script entries.

Effect of the angle of view on the reflectivity and transparency of a surface. For example, a window appears more reflective than transparent when viewed at a sharp angle.

Geometric shape used to describe the viewing volume in computer graphics, where the viewing plane sits at the top of a truncated pyramid that extends into the 3D environment.

Shading of a surface that takes into account both direct lighting and some indirect lighting, such as reflections and refractions. Ray tracing, radiosity solving, and particle tracing, account for global lighting, but in different ways. Also refers to the Ambient, Flashbulb, and Solar light settings that are grouped in the Global Lighting settings box.

Brightly-lit area on a surface caused by a specular reflection.

Specification of lighting on a surface.

In photomatching, a known point on the photograph or rendered image that correlates to a monument point in the computer model.

Text file (“.scr”) containing entries that define the names of design files, views, output filenames and formats, and rendering options for batch rendering.

Rendered image showing an intermediate result of a radiosity solving process. Constant shading is typically used to render the image to decrease processing time.

Method by which an animation parameter smoothly varies from one state to another. Also refers to the blending of adjacent pixels of a texture map for smoother rendered images.

Antialiasing technique in which samples are taken in a non-uniform manner which efficiently approximates a Poisson distribution. This distribution is particularly effective in eliminating regular-pattern artifacts, such as jagged edges, from a rendered image.

Frame in which the locations and orientations of particular elements are explicitly specified.

Most basic method of animation, in which keyframes are defined, and the system automatically computes the frames in between (a process known as “tweening”).

Shading of the surface that accounts for direct lighting only — that is, lighting directly attributed to light sources. Phong shading is an example of a rendering method that is based on local lighting.

Units in which the brightness of light sources is expressed. Lumens are the photometric equivalent of watts, but only account for energy in the visible part of the electromagnetic spectrum. If a light source's Intensity setting is 1.0, its Lumens setting closely approximates lumens.

See multi-level texture interpolation.

In photomatching, a known point in the model whose corresponding image point is visible.

Texture mapping option for Phong and ray-traced rendering that provides less noisy images and smoother animations by pre-filtering the texture into a series of progressive lower resolution images, and then smoothly interpolating between them. In an image rendered with this option, repetitive patterns fade to constant as the distance from the camera increases.

Video standard for television systems in the United States, Canada, and Japan.

Animation script whose entries are listed in the Animation Producer settings box. The open script can be previewed and recorded.

Dominant video standard for television systems in Europe and Australia.

To manipulate the view cone by revolving either the camera about the target (horizontally or vertically), or vice-versa.

Animation method in which the position and orientation of elements are mathematically specified as a function of time.

Global lighting method that computes a view-independent solution that includes all lighting effects such as color bleeding, specular light effects including reflections, refractions and caustics.

For radiosity solving, a subdivision of a surface that “shoots” light energy to each of the triangular elements of other surfaces. Each patch is subdivided into one or more elements.

Process of matching a model's viewing perspective to that of a photograph or rendered background image, which is attached to the model as a reference raster file. The expected result is a composite image in which the model is superimposed on the background image with correct positioning and orientation.

Random set of points with the property that no two points are closer together than a given fixed distance. This distribution is expensive to compute, but is generally regarded as the optimal sampling pattern for computer graphics. Jittering is commonly used to generate a point set that approximates a Poisson distribution, but with significantly less computation.

Special type of bump map that dynamically calls a procedural texture function to compute a perturbed surface normal rather than performing a lookup into a stored image.

Special type of pattern map that dynamically calls a procedural texture function to compute pixel color rather than performing a lookup into a stored image.

Function that takes either a 2D texture coordinate or a 3D world coordinate as input, and returns a texture value (either a color for a pattern map or a normal for a bump map). The function can perform anything from a simple lookup into a standard texture map to a very complex calculation. When a solid to which a 3D procedural texture is applied is rendered, the solid appears to be sculpted from the specified pattern rather than wrapped with the pattern.

Total power (light energy per unit time) per unit area leaving a point on a surface. See also radiosity solving.

See rendering database.

3D view independent lighting solution calculated using radiosity solving.

Global lighting method that accurately calculates the distribution of light energy in an environment by accounting for both direct lighting and diffuse inter-reflections. Radiosity solving is particularly useful for handling effects such as color bleeding and indirect lighting.

Photorealistic rendering method in which the global lighting of an environment is computed by simulating the reflection and refraction of light rays (recursively), using the principles of geometric optics. The output of ray tracing is a 2D view-dependent image. Ray tracing accurately depicts reflections, refractions, and semi-transparent materials.

Data structure containing the geometry and settings that are constructed in memory during pre-processing for ray tracing, radiosity solving, or particle tracing. The rendering database is kept in memory, automatically, when repeatedly rendering the same design.

Rotate the camera about the view Z-axis.

In radiosity solving, the process of examining a point on the current light source or shooting patch. The computation time increases roughly one-for-one with the number of samples. In antialiasing, the process of examining part of a pixel. Samples are combined into a final pixel value. The number of samples and the threshold at which sampling stops are adjustable settings.

Text file (“.msa”) that contains animation script entries — directions concerning keyframes, views, parameter definitions, settings, actors, animation cameras, and targets.

In radiosity solving, the process of transporting light energy from a single patch to each of the elements of the other surfaces.

Type of reflection that sends light primarily in a single outgoing direction related to a single incoming direction by the principles of geometric optics, resulting in either a mirror-like reflection or a glossy highlight. Specular reflection is said to be view-dependent.

Line separating light and dark on curved surfaces, most noticeable when an object is illuminated by a single light source.

Stored image used for texture mapping.

Process of applying detail to a surface without explicitly modeling it as part of the geometry of the surface. This process can be either a standard lookup into an image texture map or a function call to compute a value algorithmically. The resulting value can be used either as a pixel color value (as in a pattern map) or as a perturbed surface normal (as in a bump map).

In keyframing, the process in which the system automatically computes the frames in between keyframes.

Regular distribution of samples, equally spaced in all dimensions.

Rate of change of an animation parameter as it varies from one state to another.

Dynamically displayed indication of view extents that is used to set up the camera.

Global lighting of a 3D environment that varies from image to image as the position of the view is changed, primarily because of specular reflections or refractions of visible surfaces.

Global lighting of a 3D environment that remains constant from image to image as the position of the view is changed, thereby allowing for reuse, which significantly shortens the rendering time of subsequent images.

See view cone.