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

Technique in the dihedral system that rotates a plane about one of its traces until it coincides with a reference plane, revealing true shape and size of figures lying in it.

Set of rules for placing lines, arrows and numbers on a drawing so that every measurement of the object is stated once, clearly and unambiguously, following standard conventions.

Orthographic view obtained by projecting the object onto the vertical plane from the front, chosen as the principal view because it shows the most characteristic shape.

Parallel projection method in which the object is tilted relative to the projection plane so three dimensions appear at once, keeping parallel lines parallel and preserving measurable ratios along axes.

Oblique axonometric where the front face is drawn parallel to the picture plane at true shape, and depth is projected along a single receding axis, usually at 30, 45 or 60 degrees.

Central projection in which receding parallel lines converge at vanishing points, reproducing how the eye sees space; defined by the station point, picture plane, horizon line and ground line.

Numerical value written on a dimension line expressing a real measurement of the object in the units declared on the drawing, independent of the scale used to print it.

Factor applied to measurements along the axonometric axes so a projected drawing matches true length; in isometric projection it is approximately 0.816, though isometric drawings often use 1.

Hand-drawn representation made without instruments, keeping proportions and correct views, used to capture an idea or take measurements before producing a scaled technical drawing.

Bordered area of a technical sheet containing identification data: title, author, scale, date, projection method symbol, sheet number and revisions, placed according to format standards.

Flat pattern obtained by unfolding the faces of a solid onto a plane, used to cut and fold sheet material such as packaging, ducting or metal enclosures.

Orthographic projection method using two perpendicular planes, horizontal and vertical, whose intersection forms the ground line; the object is projected onto both and the horizontal plane is then rotated down to flatten the drawing.

Ratio between a drawn length and the corresponding real length, written as 1:n for reduction, n:1 for enlargement or 1:1 for full size, and applied uniformly to every dimension on the sheet.

Triangular ruler with several graduated scales used to read and transfer measurements directly, avoiding arithmetic conversion when drawing at reduced or enlarged sizes.

Apparent shortening of lines or surfaces that recede from the viewer, caused by projection; it explains why circles become ellipses and equal lengths look unequal in perspective.

Standardised paper size of the ISO A series, from A0 to A4, based on a root rectangle whose sides keep a ratio of one to the square root of two when halved.

Line or curve shared by two surfaces where they meet; finding it is the key step for solving roof meetings, pipe joints and for obtaining accurate developments.

Axonometric system with three axes at 120 degrees to each other, giving equal foreshortening on all three; widely used in technical illustration because it reads clearly and is easy to construct.

Horizontal line in a perspective drawing marking the height of the observer's eye; all vanishing points for horizontal lines lie on it and object heights relate to it.

Body of agreed rules, issued by bodies such as ISO, UNE or CEN, fixing formats, line types, symbols, dimensioning and representation conventions so drawings are understood internationally.

Published technical standard, Spanish UNE or international ISO, that specifies how a drawing element must be drawn or annotated; compliance is expected in professional and exam work.

Orthographic view projected onto a profile plane, showing the object from the side; in first-angle layout it is placed on the right of the front view, in third-angle on the left.

Conical perspective variants with one or two vanishing points; one-point suits frontal interiors and façades, two-point suits corners of buildings and objects seen obliquely.

Orthographic view seen from above, projected onto the horizontal plane; it shows widths and depths and is aligned vertically under or over the front view in a multiview layout.

Solid bounded by flat polygonal faces meeting at edges and vertices; regular examples are the five Platonic solids, and truncated or stellated forms are common in design exercises.

Point on the horizon where the projections of a family of parallel receding lines converge in conical perspective; each direction of space has its own vanishing point.

Representation that imagines the object cut by a plane and removes the nearer part, so hidden interiors appear as solid outlines; the cut surface is hatched and the cutting plane is marked on other views.

Coherent set of projection rules, such as dihedral, axonometric or conical, that fixes how a three-dimensional object is mapped onto a plane and what properties the image preserves.

Solid generated by rotating a plane figure about an axis, such as a cylinder, cone, sphere or torus; its views and developments follow directly from the generating curve.

Surface containing straight lines along its whole extent, such as cylinders, cones, hyperboloids and ruled shells; these lines make it easy to triangulate for development and construction.

Contact between two curves or between a curve and a line at a single point where they share the same tangent direction; central to enlaces, ovals and smooth design outlines.

Smooth transition between two lines, arcs or a line and an arc, built by locating the centre equidistant from both elements and drawing the connecting arc tangent to each.

Set of all points satisfying a stated geometric condition, for example the perpendicular bisector, the parabola or the locus of centres of circles tangent to two given lines.

Division of a segment into two parts such that the whole relates to the larger part as the larger relates to the smaller, a ratio of about 1.618 used in proportion and layout.

Closed curves made of tangent circular arcs: the oval is symmetric on two axes and used for ellipses drawn with a compass; the ovoid has only one axis of symmetry, like an egg.

Standardised line class and thickness, such as continuous thick for visible edges, dashed for hidden edges, chain for axes or cutting planes, chosen to make the drawing hierarchy readable.

Quick exploratory drawing of a design idea, often in colour or loose line, focused on concept, composition and overall form rather than exact measurement or standard conventions.

Network of horizontal and vertical guides, often modular, used to align elements, control proportions and keep margins consistent across a layout or a series of pages.

Deliberate ordering of elements by size, weight, colour, contrast or position so the viewer reads the message in the intended sequence before noticing secondary information.

Paired colour and value principles: contrast separates elements and creates emphasis through difference, while harmony relates them through shared hue, tone or saturation for unity.

Circular arrangement of hues showing their relationships; complementary colours sit opposite, analogous colours adjacent, and schemes are built from these positions plus value and saturation changes.

Visual or tactile quality of a surface, produced by material, pattern or simulated grain; in design it adds depth and identity and can be real, photographic or generated digitally.

Sequence of drawn frames showing successive moments of a narrative, animation or interaction, annotated with camera, timing and sound notes to plan the final production.

Written document accompanying a design solution that states objectives, references, methodology, technical decisions, materials and justification, linking the visual proposal to its reasoning.

Use of software to build precise two- or three-dimensional geometry, edit it parametrically, generate views, sections and dimensions, and exchange files for production or rendering.