Galicia PAU Technical Drawing Applied to Plastic Arts and Design II key terms

In dihedral projection, the rotation of a plane onto a projection plane so its true shape and size can be drawn. Used to solve problems on oblique planes without distortion.

Two-plane orthographic projection method using a horizontal and a vertical plane at right angles. Points, lines and surfaces are represented by paired projections linked by reference lines.

The line where a plane, line or surface intersects a projection plane. In dihedral system, a plane is defined by its horizontal and vertical traces meeting on the ground line.

The straight line of intersection between the horizontal and vertical projection planes in dihedral system. It serves as the reference from which heights and distances are measured.

The actual size of a segment, angle or surface, obtained through auxiliary views, rotations or abatements when the projection shows it foreshortened or distorted.

A projection onto a plane not parallel to the principal planes, used to show a slanted face or edge at true size. Common in technical drawing of bevelled or inclined parts.

A parallel projection in which the three coordinate axes appear at 120 degrees to each other, with equal foreshortening along each. Widely used for quick three-dimensional sketches of products and assemblies.

A parallel projection of an object onto a plane inclined to its main axes, so three faces are visible in one view. Subtypes include isometric, dimetric and trimetric systems.

An oblique parallel projection where the front face is drawn true size and depth is shown by receding lines, usually at 45 degrees and half scale. Useful for objects with detailed frontal faces.

In linear perspective, the point on the horizon where parallel lines receding from the viewer appear to converge. One-point and two-point perspectives use one or two such points.

The line in a perspective drawing marking the viewer's eye level. It contains the vanishing points and determines whether objects are seen from above, below or at eye level.

The imaginary cone radiating from the viewer's eye that defines the area of a scene perceived without excessive distortion. Perspective constructions usually keep the subject within roughly 60 degrees.

The ratio between a drawn dimension and the corresponding real dimension, such as 1:2 for reduction or 2:1 for enlargement. Stated on the drawing and applied consistently to all measurements.

A graduated bar drawn on the sheet that allows distances to be measured directly, remaining valid if the drawing is reproduced at a different size. Often combined with a numerical ratio.

The set of conventions for placing numerical values, dimension lines, extension lines and arrowheads on a drawing so sizes are unambiguous. Values are given in the drawing's real units, independent of scale.

The permissible variation in a dimension or form beyond the nominal value, stated as limits or as an upper and lower deviation. Essential for specifying manufactured parts and assemblies.

The standardized use of continuous thick lines for visible outlines, dashed lines for hidden edges, and thin chain lines for axes and symmetry. Consistent weighting makes drawings readable at a glance.

A drawing in which a cutting plane removes part of the object to reveal internal features. The cut surface is shown hatched, and hidden lines are usually omitted in that area.

The proportion approximately 1:1.618, obtained when a segment is divided so the whole relates to the larger part as that part relates to the smaller. Frequently used in composition and layout.

The set of all points satisfying a given condition, such as the perpendicular bisector of a segment or the parabola of points equidistant from a point and a line. Basis for many construction problems.

The contact between a line and a curve, or two curves, at a single point where they share a common tangent direction. Constructions rely on the radii meeting at right angles at the contact point.

Curves obtained by cutting a cone with a plane: ellipse, parabola and hyperbola. Defined geometrically by focus and directrix, they appear in design problems involving lenses, arches and orbits.

A system of horizontal and vertical guides dividing a layout into consistent units. It aligns typography, images and margins across a composition, from a poster to a multi-page publication.

A grid of evenly spaced horizontal lines to which lines of text are aligned. It keeps type at a consistent rhythm across columns and pages of a publication.

The deliberate ordering of text elements by size, weight, colour or position so the reader knows what to read first. Builds clear visual navigation through a layout.

Adjusting the space between individual pairs of letters so they appear evenly spaced, as in the pairs AV or To. Distinct from tracking, which adjusts spacing across a whole run of text.

The vertical distance between successive baselines of text. Increasing it improves readability of dense copy; decreasing it can create a tighter, more editorial texture.

A written statement of the problem, target audience, constraints, deliverables and success criteria agreed before design work begins. It anchors later decisions and justifies the proposed solution.

A collection of images, colours, textures and type samples that communicates the intended visual direction of a project. Used to align a client and designer before detailed work starts.

The cyclical process of sketching, testing, receiving feedback and refining a design. Each cycle narrows the options and improves the solution before final production.

Front, top and side views of an object drawn without perspective distortion, showing true shapes of faces. Standard practice for communicating a product's geometry to manufacturers.

A drawing in which the components of an assembly are separated along an axis to show how they fit together. Frequently used in instructions, catalogues and design presentations.

A preliminary physical or digital model built to test form, function or usability before mass production. Ranges from paper mock-ups to working 3D-printed parts.

A limited, deliberate set of colours chosen for a project, defined by hue, value and saturation relationships. Ensures visual coherence across media and supports the intended mood.

Value is the lightness or darkness of a colour; saturation is its intensity or purity. Together with hue they form the three dimensions used to describe and compare colours.

A system for describing colours numerically, such as RGB for screens, CMYK for print or Pantone for spot colour. Choosing the right model prevents surprises between screen and printed output.

A realistic or stylized image generated to show materials, lighting and surface finish of a design. Helps clients judge a product before it exists physically.

Organizing drawing elements onto named layers with controlled visibility, colour and line weight. Keeps complex drawings editable and allows selective plotting or sharing.

A reusable collection of grouped objects, such as furniture, arrows or hardware, inserted repeatedly into drawings. Editing the master updates every instance and saves time.

Building a 3D model from dimensions and constraints so that changing a parameter regenerates the geometry. Common in product design for rapid variants of a base shape.

Vector graphics describe shapes with mathematical paths and scale without loss; raster images are pixel grids that blur when enlarged. Design workflows combine both formats appropriately.