ONLINE GLOSSARY

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• Parallelism. The state of being parallel, where two objects are perfectly aligned with one another and face in the same direction. If two lines are parallel, they are equidistant from one another at all times. Such lines neither converge nor diverge. Even if the lines were extended to infinity, this alignment would be maintained along their entire length.
  
  
• Partial Section. A section view that depicts less than one half of a feature or subject. When an object is perfectly symmetrical, a half section may be used to describe its structure while taking up less space in the drawing. For some subjects that have radial symmetry (such as a wheel), even less information may be required. In such cases, a partial section may be used to describe only a pie-shaped piece of the object.
  
  
• Partial View. A portion of a normal view. If a subject is perfectly symmetrical, it may not be necessary to describe the entire object. If space is limited, a partial view may suffice.
  
  
• Pasteboard. The total drawing area available inside a computer illustration program. All pages or sheets that make up a drawing must fit on the pasteboard. Also known as the "virtual drawing canvas" or "canvas." This term originates from the traditional method of creating print layouts by hand using paper and paste on a work surface such as a drawing table.
  
  
• Pixels. A tiny region or "dot" that makes up a digital image. Unlike a television screen that has a picture made up of scan lines, images on computer monitors are broken down into individual dots called pixels. Each dot can appear white, black, a shade of gray, or any one of millions of possible colors. Because of this, all digital images must be stored as a pattern of pixels so they can be displayed on screen. When an image is scanned or "digitized," the computer divides it into tiny little regions and records both the color and the light/dark value of each region. These values are then assembled to create a digital image file. See also Bitmap Image.
  
  
• Plan View. An "orthographic" representation of a subject from a particular angle or point of view. Orthographic renderings are prepared in such a way that distortion caused by visual perspective is completely eliminated. An orthographic plan view can be any one of the six principal plan views (top, bottom, front, rear, left, and right) derived from the three principal planes of projection. See Orthographic Projection.
  
  
• Plane. A perfectly flat surface. Because it is perfectly flat, a plane is actually a two-dimensional object but can be oriented in any direction in three-dimensional space.
  
  
• Plans. Blueprints created for the purpose of building a scale model of a subject.
  
  
• Platonic Solids. Five special types of regular polyhedrons (or "polyhedra") where the same number of sides or "facets" always come together at each point or vertex. These geometric figures – named after the Greek philosopher Plato – are unique because every side, angle, and edge is the same all around the object. The five Platonic Solids are the tetrahedron, cube, octahedron, dodecahedron, and icosahedron.
  
  
• Polygon. In geometry, a two-dimensional figure with three or more sides. In 3D modeling, the polygon is the basic element that makes up a mesh surface. See Multigon.
  
  
• Polyhedron. A three-dimensional area of space enclosed by a series of flat surfaces or "facets" that are joined together at the edges (i.e. a "closed" surface). Each face of a polyhedron is a multigon. See also Platonic Solids.
  
  
• Presentation Plans. Blueprints that depict only the overall form of a subject, but not the structural detail needed to recreate it.
  
  
• Primary Auxiliary View. A true-size view of a non-principal plane or surface projected from an auxiliary plane of projection. The primary auxiliary view is derived from information contained in the normal plan views via orthographic projection. In contrast, a secondary auxiliary view is derived from information contained in a primary auxiliary view.
  
  
• Principal Plan Views. The six orthographic views projected onto the sides of an imaginary "glass box" surrounding a subject using orthographic projection. These are the top, bottom, front, rear, left, and right views. All six principal plan views are normal views.
  
  
• Principal Plane. A normal plane.
  
  
• Principal Planes of Projection. Three planes of projection from which the six principal plan views are derived. According to the theory of orthographic projection, an imaginary "glass box" can be placed around a subject and the six principal plan views projected onto the six sides of this box. Each side of the box is therefore a plane of projection. Since views on either side of the imaginary glass box are parallel to one another, the plane of projection that yields a view on one side is parallel to the plane of projection that yields the view on the opposite side. As a result, the six planes of projection can be reduced to just three principal planes of projection.
  
  
• Prism. (Pronounced "PRIZ-uhm") A three-dimensional shape with a base and top made from identical multigons and where the sides are either rectangles or parallelograms.
  
  
• Profile. In a 2D drawing, a cross section outline appearing in the side plan view. A profile is created by passing a cutting plane through an object where the cutting plane is parallel with the profile plane of projection. In a spline-based 3D modeling program, a profile is a two-dimensional line, curve, or other shape used to create a three-dimensional surface using 3D tools such as extruding, lofting, sweeping, or lathing.
  
  
• Profile Plane. One of the three principal planes of projection that yields the left and right side plan views. Since both views are parallel to one another, the plane of projection that yields the left plan view is parallel to the plane of projection that yields the right plan view. As a result, these planes of projection can be combined into a single plane known as the profile plane.
  
  
• Projected View. An outline projected onto the side of an imaginary glass box surrounding a subject using the techniques of orthographic projection.
  
  
• Pyramid. A three-dimensional shape where the base is a multigon and the sides are triangles that meet at a point.

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0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Click on a letter to browse through the Glossary terms.
To download a printable version of the entire Glossary, click here.

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