(See related pages)
Glossary Terms S thru Z
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| saturation | (n) A perceptual color quality indicating the ratio of the primary spectral wavelength (the hue) to all the wavelengths in the color. A high saturation color has a vivid hue, whereas a low saturation color approaches gray in appearance. |
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| scalar value | (n) A quantitative data type that expresses magnitude but not direction. |
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| scale | (n) A measuring tool used to calculate distances on a technical drawing. Scale can refer to both the physical tool, similar to a ruler, and the mathematical ratio used to calculate the size difference between the actual object and the drawn representation of the object. Scale lines in a visualization map the scale values to the graphic figure. |
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| scale breaks | (n) Interruptions, or breaks, in a visualization scale, used to reduce large blank areas in the visualization created by widely dispersed data. Scale breaks allow a visualization to preserve a larger magnification by reducing the area required for the drawing. |
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| scanner | (n) A computer input device used to capture information on paper and translate the information into a raster (bitmapped) computer image. Scanners can be used to convert a drawing created with traditional tools to a CAD drawing, to convert and enhance photographs in desktop publishing, or to input text information into the computer. |
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| scatter plot | (n) A visualization technique that maps discrete values with point marks in either 2-D or 3-D space. A regression line is often included in the visualization to help recognize data trends. |
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| schematic (logic) drawing | (n) A type of drawing or diagram commonly used in electronics to represent the logical and functional relationships of parts in an electronic assembly, circuit, or device. The drawing details the signal flow and control but not necessarily the spatial relationship of the final layout nor the actual point-to-point wiring that will be used. Special design symbols are used to represent the different types of electronic components. |
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| screen angle | (n) The alignment angle of dots in halftone images. The angle of the dots in an image, especially when multiple screens are being used, is critical for avoiding illusionary and otherwise unwanted secondary patterns from appearing in the printed image. |
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| screen coordinate system | (n) A coordinate system used to map graphics created by the computer software to the monitor. The coordinate system often has its origin in the upper left-hand corner of the screen, with the measurement unit in pixels. |
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| screen print drawing | (n) See fabrication drawing. |
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| seam line | (n) Lines on a development that indicate where material is to be folded to create areas of joinery with other surfaces. |
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| secondary auxiliary view | (n) An auxiliary view projected from a primary auxiliary view. Secondary auxiliary views are used to depict oblique surfaces in their true size and shape. |
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| section assembly | (n) An assembly drawing that provides a general graphic description of the interior shape of an assembly by passing a cutting plane through the assembly. The section assembly is usually a multiview drawing of all the assembled parts, with one view in full section. Other types of sections can also be used, such as broken-out and half sections. |
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| section drawings | (n) Drawings containing views in which portions of the object have been removed. Section drawings typically depict the cutting plane used to define the removed material in a view adjacent to the actual section view. The section view depicts the cut surfaces with section line symbols. |
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| section lines | (n) A line used to represent surfaces of an object cut by a cutting plane in section views. Section lines are drawn in a number of patterns (symbols) corresponding to the type of material being sectioned. |
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| section views | (n) Types of multiview drawings used to improve clarity and reveal interior features of parts and assemblies. |
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| serial slices | (n) A visualization technique based on sectioning. A 3-D object is reduced to a series of 2-D images by representing two of the geometric dimensions in all slices, and each slice represents a discrete value range for the third geometric dimension. |
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| servicing | (v) An activity that supports the installation, training, maintenance, and repair of a product or structure for the consumer. Technical illustrations are found in manuals used to support servicing activities. |
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| set screw | (n) A mechanical threaded fastener, with or without a head, used to prevent rotation or movement between parts, such as a shaft and a collar. Set screws have special types of points for different applications. |
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| shading | (v) A rendering technique simulating the effect of light on the surface of an object. The angular relationship between the light and the surface results in a variance in the value (darkness/lightness) of the surface. Abrupt changes in value typically indicate an edge between surfaces (faces). |
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| shadow casting | (v) A rendering technique used to simulate shadows cast by (a) light source(s). Based on methods similar to hidden surface removal, the direction of the light rays is used to calculate which surfaces are nearest to the light source (and thus generate the shadow) and which are behind the near surfaces (and thus receive the shadow). |
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| shaft basis | (n) A tolerancing technique used to define a system of fits and based on the basic size as being the maximum size of the shaft. |
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| shape | (n) The internal spatial relationship of vertices and edges that make up a face or the arrangement of faces on an object. Examples of characteristics used to describe a face are the number of edges (sides), the angle between edges, and the ordering of edges around the perimeter. Shape is independent of overall scale but not of viewpoint. |
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| shear | (n) Acronym for System Internationale (i.e., International System of Units), the metric measurement system. For technical drawings using the SI units, the millimeter (mm), meter (m), and the kilometer (km) are the most common units of measure. The international organization that established the metric standard is the International Standards Organization (ISO). |
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| single-curved surface | (n) A surface that curves in only one dimension. A cylinder is an example of a single-curved surface. Single-curved surfaces can be developed without distorting or altering the topology of any of the faces. |
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| single-line drawing | (n) See piping drawing. |
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| size | (n) The spatial dimension of an object. When used with a dimension (i.e., inches, centimeters), size refers to an absolute
measurement. Size can also be used in a relative sense to compare features or objects. |
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| sketch modelers | (n) A term used to describe computer modeling systems used in the ideation phase of the design process. Sketch modelers are defined by their ability to produce approximately accurate models quickly and easily. |
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| skew lines | (n) Nonintersecting, nonparallel lines in 3-D space. The relationship of skew lines, such as the shortest distance (clearance), can be calculated using descriptive geometry techniques. |
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| software | (n) A set of coded instructions (programs) used to control the operation of a computer. Software is often grouped into categories, such as operating systems (e.g., MSDOS), application programs (e.g., the CAD program), and utilities (e.g., security programs). |
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| soldering | (v) See brazing. |
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| solid geometry | (n) The geometry of 3-D objects, such as cylinders, cubes, and spheres, and their relationships. |
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| specifications | (n) The precise description of a property of an object or design. For example, specifications concerning the weight and overall dimensions for a proposed engine. Specifications may also give instructions concerning a process. |
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| specular reflection | (n) Light reflecting from a surface at the same angle at which it contacted the surface. With a perfect mirror, 100 percent of the light is reflected in this manner. Specular refections are responsible for highlighting, or hot spots, seen on real objects and rendered models. |
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| spherical coordinates | (n) Coordinates used to locate points on a spherical surface. Spherical coordinates are described by specifying a distance and an angle from the origin measured in the X–Y plane and then an angle from the X–Y plane. |
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| spiral | (n) A curved line that begins at an origin point, moves further away from the origin, and decreases in curvature as it travels around the origin. A spiral is sometimes referred to as a spiral of Archimedes. |
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| spline | (n or v) A free-form curve that connects a series of control points with a smooth curve. Changing a control point results in a change in the curve. The term also describes the process of connecting points to create a curve. B-spline and Bezier curves are examples of spline curves. |
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| spooling drawing | (n) A piping drawing that gives the information necessary for the construction of a subassembly of an overall piping system. These drawings are used off site to fabricate subassemblies that can then be taken to the project site for final assembly. |
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| spot enlargements | (n) Drawings used in conjunction with larger technical illustrations of parts or assemblies to show a clearer view of critical features. Spot enlargements typically use a combination of increased scale, reverse views, and sectioning to aid in viewing a feature. The enlargement is usually on the same sheet as the overall illustration, is isolated by ruled lines, and is keyed back to the overall drawing by a leader or a separate callout. |
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| spot light source | (n) A light source located at a specified point and orientation in pace. In rendering, a spot light source is usually close to the model. Besides a location and an orientation, the user also specifies an angle of dispersion to create a cone of light. A flashlight is analogous to a spot light source. |
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| spring | (n) A mechanical device, often in the form of a helix, that expands or contracts due to pressure or force. Springs are classified as compression, tension, extension, flat, and constant force. A spring is further classified by the material, gage, spring index, direction of the helix, and type of ends. |
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| Standard for the Transfer and Exchange of Product Model Data | (n) See STEP. |
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| standards | (n) Sets of rules that allow for the clear communication of technical ideas by governing how parts are made and represented in technical drawings. In the United States, the American National Standards Institute (ANSI) is the governing body that sets the standards used for engineering and technical drawings. |
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| statics | (n) An area of applied physics that deals with the analysis of forces in bodies (parts) at rest (in equilibrium). |
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| station point | (n) The eyepoint of the observer in a perspective drawing. The location of the station point relative to the object, and the horizon line determines the perspective viewpoint (i.e., bird’s eye, human’s eye, etc.). |
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| statistical process control | (n) The system used for the selection of parts that are then measured for accuracy. Mathematical statistics is the tool used to analyze the measurements of the randomly selected parts. Consistent and accurate measurements will indicate when a machine tool must be maintained or adjusted during the manufacturing cycle. |
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| steel | (n) An alloy of iron, containing various amounts of carbon, manganese, and one or more other elements, such as sulfur, nickel, silicon, phosphorus, chromium, molybdenum, and vanadium. These elements, when combined with iron, form different types of steels with varying properties. |
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| STEP | (n) An acronym for Standard for the Transfer and Exchange of Product Model Data, a neutral data exchange standard developed by the ISO. The development of this standard is an attempt to integrate the European standards and IGES and to embody a larger, more flexible subset of information. |
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| stereolithography | (n) A rapid prototyping technique in which the model is first decomposed into a series of thin layers and then reconstructed. A pair of light beams moves a focal point about in a vat of photosensitive polymer, tracing one layer at a time. Once one layer of polymer has been hardened by the light beams, the light beams trace the next layer up. |
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| stereoscopic display | (n) A (computer) display that makes use of the perceptual effect of stereopsis: the disparity between the projected image received by the right and left eyes. Different computer images are sent to the two eyes through special monitors and/or headgear covering the eyes. |
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| straight line | (n) A line generated by a point moving in a constant direction. Straight lines can be either infinite or finite in length. A finite straight line is an entity of specific length but no depth or breadth. An infinite straight line is an entity of unspecified length but no depth or breadth. |
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| straightness | (n) A form control for geometric dimensioning and tolerancing. Straightness means that all points on a part have the same direction throughout its length. Straightness also refers to the path describing the shortest (uniform) path between two points. |
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| streamlines | (n) Line marks, usually curved, used in visualizations to depict the path of flow of a fluid or gas. Streamlines are used in aerodynamic studies to evaluate the flow of air or water around a proposed design. |
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| stretching | (v) A modification technique that changes the location of individual points or groups of connected points of an object. Stretching changes the geometry but not the topology of the polygon or face of the solid. If this technique is used on a 3-D solid, it is sometimes referred to as tweaking. |
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| stud | (n) A mechanical fastening device that consists of a cylindrical rod threaded on one or both ends and that screws into a mating part. A nut may be used on one end. |
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| subassembly | (n) A logical grouping of parts that are only part of the total assembly. Often, a subassembly is a working mechanism in and of itself, but it works in concert with other parts to form the complete assembly. |
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| subtractive | (adj. or v) A process or state in which elements are removed from each other. Subtractive is the opposite of additive. |
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| subtractive primaries | (n) The three primary colors cyan, magenta, and yellow. Color systems using these primaries work on the principle of subtracting spectral wavelengths from the light energy to create new colors. These systems are used in ink-based graphics, specifi-cally four-color printing (the fourth color being black). The complementary colors are the additive primaries: red, green, and blue. |
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| successive auxiliary view | (n) An auxiliary view of an object created by projecting from other auxiliary views. With the use of successive auxiliary views (e.g., secondary auxiliary, tertiary auxiliary, etc.), it is possible to create virtually any view of an object. |
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| surface | (n) A finite portion of a plane, or the outer face of an object, bounded by an identifiable perimeter. A surface represents the path of a moving straight or curved line, called a generatrix. The path that the generatrix travels is the directrix. In a 3-D model, the topological equivalent of a surface is a face. |
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| surface of revolution | (n) A specific type of swept surface where a curve (generatrix) is propagated about a circular path (directrix). The directrix is specified by an axis relative to the generatrix and the degree of rotation. |
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| surface plot | (n) A 3-D visualization technique used with two independent variables (X and Y) and one dependent variable (Z). A surface connecting the data points represents the mapping of the independent and dependent variables. Shading and other rendering techniques are often used to help visualize the surface. |
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| sweeping | (n) A 3-D modeling operation in which a closed polygon, called a profile, is drawn on the workplane (the U–V plane) and is transformed along a defined path. The sweeping technique is procedural in nature in that instructions are given as to how far and in what direction the sweep of the profile is to occur in order to create the solid. |
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| swept surface | (n) A surface generated by a curve (generatrix) being propagated along a path (directrix). This technique is very common in 3-D modeling programs for the generation of 3-D surfaces and solids. Typically, an open loop generatrix creates a surface while a closed loop generatrix forms a solid. |
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| symmetrical | (adj.) A quality in which all the features on either side of a point, line, or plane are identical. The matching features form balanced, mirror images. |
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| system | (n) An orderly arrangement of parts that are combined to serve the same general function. Examples are the arrangement of the
assembly process in a factory; the heating, ventilating, and air conditioning (HVAC) system in a structure; and the electrical system in an automobile. |
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| Tablet | (n) A computer input device used to control cursor movement and to select menu items. The tablet can be covered with a thin, plastic overlay that contains the menu options for a CAD software program. Attached to the tablet is the cursor control device, such as a puck or stylus. Specialized tablets, called digitizers, are used to convert a drawing created with traditional tools to a CAD drawing by tracing geometric elements with the puck. |
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| tabular drawing | (n) Used to indicate the dimensions of a family of parts. Dimensions are given alphanumeric codes which are then referenced in a table. Different dimension values are applied to the general dimension depending on which member of the part family is being referenced. |
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| tangent | (n) A condition in which a straight line is in contact with a curve at only one point. Tangents describe the smooth transition from a linear/planar element to a curved one. Geometric construction techniques are used to define tangent curves in an engineering drawing. |
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| tap | (n or v) The machine tool used to make threads in holes. A drill bit (the tap drill), approximately equal to the diameter of the crest, is used to make a hole in metal before tapping an internal thread. The term is also used to describe the process of creating the threads. |
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| technical and office protocol | (n) See TOP. |
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| technical drawing/graphics | (n) A specialized type of graphics used to communicate technical information. Examples of technical raphics include 3-D computer models and illustrations of a technical device. |
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| technical illustration | (n) A drawing that communicates the functionality or assembly of a product. These illustrations traditionally were axonometric pictorials done in black and white supporting portions of the product development, manufacture, and support cycles where succinct, non-dimensioned drawings were needed. More recently, a broader array of multimedia technologies have been deployed to represent technical and scientific information other than information directly related to the design and production of a product. |
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| technical reports | (n) In-depth accounts, containing text and graphics, documenting the design process. Progress reports are created in the early stages of the design process to document the decisions made by the design team and are used to periodically review the status of a project. Final reports are written at the end of the design cycle and are much more detailed. |
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| technical sketch | (n) A type of sketch that depicts only certain features of an object or structure. Sketches are used as part of the design process, in the same way as a technical drawing, but sketches are more informal and are typically used early in the design process. |
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| technologists | (n) Personnel who work with the engineers and are concerned with the practical aspect of engineering in planning and production. The technologist must be able to communicate quickly and accurately using graphics, by sketching design problems and solutions, analyzing design solutions, and specifying production procedures. |
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| telepresence | (n) The experience of being present at a live, real world event when physically being located at some other remote location. |
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| template | (n) A die-cut flexible sheet used to assist in the drawing of repetitive features, such as circles, ellipses, threaded fasteners, and architectural symbols. The circle template is used to draw regular-interval sized circles and arcs (e.g., 1-mm increments) quicker than using a compass. |
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| tensor | (n) A general term describing all types of quantitative data. A tensor has two parts: the dimensionality of the coordinate system, d, and the order of the tensor, n. The number of components (scalar values) needed to express the tensor is equal to dn. For example, a 2-D vector is a tensor of order n = 1 with 21 = 2 components. |
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| tertiary auxiliary view | (n) An auxiliary view projected from a secondary auxiliary view. |
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| text alignment | (n) The vertical alignment of lines of text. Also referred to as justification, lines of text can be aligned along such features as their right or left ends or the centers of the lines. |
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| texture gradient | (n) A perceptual cue that uses changes in patterns to indicate changes in a surface (face). Gradual changes in the patterns indicate changes in depth, curvature, orientation to light, or a combination thereof. Abrupt changes indicate a change of surfaces or objects. |
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| texture mapping | (n) A rendering technique that transfers a 2-D pattern (texture) to a 3-D surface. Although the name implies manipulating the geometry of the surface, the technique is limited to mapping color patterns, such as a logo or a fabric pattern, to a surface to enhance the realism of the model. |
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| third-angle projection | (n) The arrangement of the six principal orthographic projected views as commonly practiced in the United States and Canada. The name derives from the quadrant of three mutually perpendicular planes that define the relationship between the object, viewer, and projection plane(s). |
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| thread form | (n) A threading term used to describe the profile or shape of the thread cut into the cylinder. |
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| thread series | (n) A threading term used to describe the number of threads per inch for a given diameter. |
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| threaded fastener | (n) A mechanical fastener incorporating threads as a means of joining parts, either directly by threading into one or more of the parts or indirectly by using a nut. |
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| through hole | (n) A cylindrical void (hole) that goes completely through an object such that the hole begins and ends at original boundary surfaces of the object. |
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| tick marks | (n) Short, perpendicular lines located along a primary line. Tick marks are used to mark important locations along the line, such as a point of tangency in a geometric construction or the regular divisions of units along a scale line in a visualization. |
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| time series analysis | (n) A visualization technique depicting a sequence of graphs in such a way as to allow comparisons between them. The sequence of images can be shown serially in the form of an animation or in parallel, with all the images either superimposed on each other or shown side by side. |
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| title block | (n) Used to record important information on working drawings. |
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| tolerance zone | (n) A tolerance term that represents the tolerance and its position in relation to the basic size. |
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| tool solid | (n) Transient solid objects used to modify the solid model in a modeling system. Typically representing relative simple geometric shapes, tool solids modify the solid model using Boolean operations. |
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| tools | (n) Devices used to create engineering drawings and models, including both hand and computer tools. |
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| TOP | (n) Acronym for technical and office protocol, a standard developed to assist in the integration of technical information within an office environment. TOP allows file transfer, management, and access; message handling; standards for document revision and exchange; directory services; graphics; and database management. |
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| top view | (n) A principal view of an object created by rotating the line of sight 90 degrees about the horizontal axis above the front view. This view is typically included in a standard multiview drawing. |
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| topological | (adj.) In 3-D modeling, a term that refers to the connectivity of the model, that is, how the elements of the object (i.e., the faces, edges, and vertices) are organized. Geometry specifies where elements are located in space and how they are shaped; topology describes how these elements are connected to each other. |
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| total quality management (TQM) | (n) The process of managing the entire organization such that it excels in all areas of production and service. The key is that quality extends throughout the organization, in everything that it does, and quality is defined by the customer. |
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| TQM | (n) See total quality management. |
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| traditional tools | (n) Devices used to assist the human hand in making technical drawings, such as drawing lines straighter, circles more circular, etc. Examples are mechanical pencils, straightedge scales, triangles, and compasses. Traditional tools are often compared with computer-based CAD tools. |
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| transition fit | (n) A fit that occurs when two toleranced mating parts will sometimes be an interference fit and sometimes be a clearance fit when assembled. Both the loosest and tightest fits for any two mating parts must be calculated, often using tables associated with standard parts. |
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| triangle | (n) A polygon with 3 sides. |
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| trimetric projection | (n) An axonometric projection in which none of the three axes is measured on the same scale or is at the same angle relative to the others. A trimetric drawing is the hardest to draw, but it is the most pleasing to the eye since it represents the most realistic positioning of the object. |
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| true-length line | (n) A line representing an edge that is parallel to a plane of projection and perpendicular to the line of sight. |
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| true-size plane | (n) A plane parallel to the plane of projection and perpendicular to the line of sight. The plane is shown as an edge in the adjacent, orthogonal projection planes. |
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| tweaking | (v) A general term encompassing a variety of techniques that involve changing the geometry but not the topology of an object. For example, the radius of a sphere can be changed without adding or deleting any new faces. The size of a hole can also be changed, as long as the enlargement does not cross the edges of any other faces. |
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| underconstrained | (adj.) Typically used in reference to geometry contained in a 3-D model. In an underconstrained model or feature of a model, the relationship and location of geometric elements is not unequivocally defined. |
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| undevelopable surface | (n) A surface of an object that cannot be unfolded or unrolled onto a plane without distortion. Double-curved surfaces, such as spheres, are undevelopable. |
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| unevaluated | (adj.) A description of a model for which the final form is not explicitly represented in the database. An evaluated model is concise (i.e., it takes up smaller amounts of memory), but it is not efficient since portions of the model must be defined “on-the-fly” before the user-requested operations can be processed. |
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| unidirectional dimensioning | (n) A style of dimensioning in which the dimension and note text are oriented to be read from the bottom of the drawing, relative to the drawing format. This is an ANSI approved style of dimensioning. |
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| unilateral | (adj.) Relating to, or affecting only one side. A unilateral tolerance only varies one direction from the basic size of a part (e.g., larger but not smaller). |
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| union | (n) The Boolean operation that combines the two specified solids. If the two solids intersect, the intersecting geometry is only represented once in the resulting solid. |
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| uniqueness | (adj.) A term used to describe the representation of an object by a computer modeler. The term refers to how close the correspondence is between the representation and the object and whether the representation can in fact represent more than one possible object. |
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| universal product code | (n) See UPC. |
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| UPC | (n) Acronym for universal product code, a coded symbol placed on parts and products. UPC is part of a bar coding system for automatic reading by a laser scanning device. In manufacturing, bar codes are attached to parts, assemblies, and finished products, for tracking the product and for inventory purposes. |
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| upper deviation | (n) A tolerancing term describing the difference between the maximum size limit and the basic size. |
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| validity | (adj.) A term used to describe the representation of an object by a computer modeler. The term refers to whether the representation actually represents a form that could exist in the real world. |
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| value | (n) Also known as lightness. The perceived level of reflected light coming from an object’s surface. Value is also a more general perceived quality of color describing how light or dark a color is. |
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| valves | (n) Mechanical devices used to control the flow of liquids and gases through piping systems. The four major functions of valves are to start and stop flow, regulate flow, prevent backflow, and relieve pressure. Valves can either be manual or computer controlled and can be set to respond automatically to conditions in the pipe. |
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| vanishing point | (n) An imaginary point in a perspective drawing or sketch, often on the horizon line, where all projection lines of one dimension of the object converge. |
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| vector value | (n) A quantitative data type that expresses both magnitude and direction. |
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| vertex | (n) The coincidental termination of two or more edges, defined by a point in space. This point indicates a transition from one edge to another and is often the juncture of two or more faces (surfaces). |
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| vertical plane | (n) A plane parallel to the profile plane of projection. |
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| videodisk | (n) An optical storage medium for analog video information. The disk has the advantages of efficient storage of analog information, high image quality, and almost immediate random access; it is similar in technology to the CD-ROM but larger in diameter. |
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| view camera | (n) In 3-D modeling, a metaphorical camera that records what is on the image plane and then, much like a video monitor, shows the image on the computer screen. The image from the camera is contained in a port on the computer screen. |
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| view volume | (n) A theoretical volume defining the region to be rendered. The minimum and maximum Z depths and the viewing bounds on the screen define the three dimensions of the volume. The volume appears as a rectilinear prism in parallel projection and as a truncated pyramid in perspective projection. |
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| viewport | (n) A region or window in the computer interface showing the CAD model from a particular view projection. |
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| virtual condition | (n) The condition resulting from the worst-case combination of size and geometric tolerance applied to a feature. Virtual condition is used in the design of mating parts and for determining gage element sizes. For an external feature, virtual condition is the MMC size plus the geometric tolerance. For an internal feature, it is the MMC size minus the geometric tolerance. |
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| virtual models | (n) A computer-based model analogous to a real or proposed object. Virtual models are endowed with the qualities of a real object, allowing the models to be used in evaluating a proposed design. Virtual models are useful for quickly performing multiple tests that could be destructive to physical models. |
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| virtual reality (VR) | (n) A generic term used to describe artificial environments in which some or all of the human senses are immersed. The term “presence” is often used to describe the degree to which one feels immersed in the virtual environment. VR can be used in engineering design to allow more complete examination of proposed designs without having to build physical prototypes and place them in their planned environments. |
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| visible line | (n) A line type used to represent features that can be seen in the current view. A visible line represents the boundary between two surfaces (faces) that are not tangent or the limiting element of a curved surface. |
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| visibility | (n) The clear and correct representation of the relative positions of two geometric figures in multiview drawings. |
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| visual inspection | (v) The process of evaluating a design visually. Visual analysis is often used by industrial designers and marketing professionals to assess the consumer’s aesthetic reaction to a design. This analysis can also be used by engineers to perform a quick confirmation of geometry. |
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| visual science | (n) The study of the visual and technical applications of graphics. Some of the applications of visual science include printing technologies, communications media, visual design, engineering graphics, and artistic drawing. |
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| visualization | (v) The process of mentally understanding visual information. Visualization is used with both physical and virtual models to better understand their form and function. The mental image may be analogous to the object represented or of something different. Graphics and the process of creating graphics are used to help stimulate the visualization of proposed designs. |
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| volume rendering | (n) A visualization technique used with three independent variables mapped to the three geometric dimensions. Each dependent data value is represented by a 3-D volume unit called a voxel, typically coded with color. Various sectioning techniques are used to reveal data values on the interior of the data space. |
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| voxel | (n) The minimum 3-D unit in a volume rendering; equivalent to the pixel in a 2-D rendering. |
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| VR | (n) See virtual reality. |
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| warped surface | (n) A single- or double-curved transitional surface (e.g., cylindroids, conoids, helicoids, hyperbolic paraboloids). Warped surfaces are often approximated by triangulated surface sections, and may join other surfaces or entities together. |
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| washer | (n) A round piece of material with a hole in the center, used with mechanical fasteners to improve the assembling surface, distribute load, and assist in locking nuts. Washers are specified by giving the inside diameter, outside diameter, thickness, type, and name. |
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| web (rib) | (n) A thin, flat feature of an object that acts as a structural support. Ribs, webs, spokes, lugs, and other thin features are not section lined if a cutting plane passes through their long dimension. |
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| welding | (v) To unite metallic or plastic parts by allowing molten portions of both parts to flow together. The molten state can be achieved by heating, chemicals, or hammering or compressing with or without previous heating. |
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| welding drawing | (n) A detailed multiview drawing of all the parts assemblies with accompanying welding symbols. |
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| width | (n) One of the three principal dimensions of an object. The width dimension is described in the front and top views of a multiview drawing. The width dimension is often associated with the X axis in a 3-D modeling system. |
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| winged-edge data structure | (n) A common 3-D database structure used by boundary representation (B-rep) modelers. This data structure attempts to strike a balance between conciseness and efficiency by providing select redundancy of edges and vertices. |
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| wireframe | (n) The simplest type of data representation for 3-D models. Wireframe modeling is a natural outgrowth of 2-D CAD in that such models only contain information on edges and vertices. With a wireframe modeler, there is no implicit information on the boundary between inside and outside the model volume. Wireframe can also refer to a rendering technique in which only the edges and vertices are represented in the image. |
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| wiring (cabling) diagram | (n) A diagram or drawing showing how the components in an electronic assembly will be connected. Since wiring diagrams often depict the wiring of all the components tied into a single wiring harness, they are also called cabling diagrams. When the drawing depicts how the components are connected to the cable, it is called an interconnection (or point-to-point) diagram. When there are numerous cable connections, it is called a highway diagram. |
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| working assembly drawing | (n) A drawing that combines the detail drawing with the assembly drawing. For relatively simple assemblies using some standard parts, it is possible to combine the detail drawing with the assembly drawing by using a section view. |
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| working drawings | (n) The complete set of standardized drawings that specify the manufacture and assembly of a design. Depending on the complexity of the design, working drawings may be on more than one sheet and may contain written instructions, called specifications. Working drawings are often synonymous with the “blueprints” of a design. |
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| workplane | (n) Often called a construction plane, a 2-D infinitely large plane that can be oriented anywhere in 3-D space. A workplane usually has an associated local coordinate system designated with unique letters (e.g., U, V, W). Workplanes are used to define 2-D geometry used in the development of 3-D models. |
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| world coordinate system | (n) A fixed coordinate system, also referred to as a global coordinate system, used in CAD to define the geometric properties of elements stored in the database. The world coordinate system typically uses either a 2-D (X,Y) or 3-D (X,Y,Z) Cartesian coordinate system. |
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| worm’s eye view | (n) In a perspective pictorial, a viewpoint looking up at the object. From this viewpoint, the ground line is substantially above the horizon line of the object. |
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| xerography | (n) A process for copying documents by reflecting light off the document onto an electrically charged photoconductive insulating surface in which the latent image is developed with a resinous powder. This powder, called toner, is deposited, heated and fused onto the document. Xerography is the process which photocopying is based on. |
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| Z-buffer | (n) A combination of computer hardware and software which stores depth (Z) information about a rendered model. AZ-buffer contains specialized memory for managing depth information, thus speeding the rendering process, especially in animated sequences. |