PAU Technical Drawing Applied to Plastic Arts and Design II flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Golden section ratio

Division of a segment so that the whole is to the larger part as the larger part is to the smaller; numerical value approximately 1.618, denoted phi.

Mean proportional construction

Semicircle drawn on the sum of two segments; the perpendicular erected at their junction meets the arc at a height whose square equals the product of the segments.

Thales' proportionality theorem

A line parallel to one side of a triangle cuts the other two sides into segments whose ratios are equal, allowing division of a segment into n equal parts.

Tangent from external point

Circle with diameter equal to the distance from the external point to the centre intersects the given circle at the two tangency points.

Ellipse focal relation

For an ellipse with semi-major a and semi-minor b, the focal distance c satisfies a squared equals b squared plus c squared; sum of focal radii is 2a.

Regular polygon inscribed formulas

For n sides and circumradius R, side length is 2R sin(180/n) and apothem is R cos(180/n); central angle between adjacent vertices is 360/n.

Dihedral system ground line

Intersection of the horizontal and vertical projection planes; after folding, it separates elevations above from plans below, with reference lines perpendicular to it.

True length condition

A segment appears at true length only in a view where it is parallel to the projection plane; oblique segments appear foreshortened in both principal views.

Change of projection plane

A new reference line drawn parallel to a segment's projection yields its true length in a single auxiliary view, without rotating the object.

Piercing point of line and plane

Auxiliary projecting plane through the line intersects the given plane in a line; where that line crosses the original line is the piercing point.

Plane edge-on view

A plane projects as a straight line in any view whose direction of sight lies within the plane; the perpendicular view then shows true shape.

Visibility in multiview drawing

At a crossing of two elements, the one with the smaller depth coordinate toward the observer is visible; the other is drawn dashed as hidden.

Isometric axes and scale

Three axes separated by 120 degrees with equal foreshortening; true isometric drawing uses full scale, while true projection uses about 0.816 reduction.

Cabinet oblique projection

Front face drawn true shape with the receding axis at 45 degrees; the depth dimension is halved to reduce apparent distortion.

Horizon line in perspective

Line at the observer's eye level on the picture plane; it contains the vanishing points of every horizontal line in the scene.

One-point perspective condition

The object's front face is parallel to the picture plane, so only lines running away from the viewer converge, meeting at the principal point.

Cone of vision limit

Objects should fall within roughly a 60-degree cone from the station point; wider angles cause extreme peripheral distortion in the perspective drawing.

Measuring point method

For each vanishing point on the horizon, a measuring point is set off so that true lengths along receding lines can be transferred from the ground line.

ISO A-series sheet ratio

Each sheet has sides in ratio one to the square root of two; A0 has an area of one square metre and every subsequent size halves the area.

Line types hierarchy

Continuous thick for visible edges, continuous thin for dimensions and hatching, dashed for hidden edges, chain lines for axes and cutting planes.

First-angle projection layout

Object lies between observer and plane; the top view is placed below the front view and the left-side view appears to the right.

Dimension line conventions

Arrowheads terminate both ends, extension lines stop about one millimetre short of the outline, and figures sit above the line, readable from below or right.

Hole basis fit system

The hole is designated H with lower deviation zero; the shaft letter and tolerance grade determine clearance, transition or interference fit.

Drawing scale definition

Ratio of a drawn length to the real length; 1:20 means one unit on paper represents twenty units of the actual object.

Section hatching convention

Cut material is hatched with thin lines at 45 degrees; adjacent parts in the same section are hatched in opposing directions for distinction.

Rule of thirds

Frame divided into three equal bands horizontally and vertically; placing focal elements on the lines or intersections produces dynamic balance.

Root two rectangle

Rectangle whose diagonal equals the side of a square built on its longer side; halving it repeatedly reproduces the ISO A-series proportions.

Reciprocal diagonal grid

A rectangle's diagonal crossed by the perpendicular diagonal from a corner generates proportional subdivisions used in dynamic symmetry layouts.

Optical centre

Point slightly above the geometric centre of a frame where visual balance is perceived; placing weight there feels stable to the viewer.

Gestalt proximity grouping

Elements placed close together are read as one group; spacing alone can create hierarchy without any change in size or colour.

Modular coordination base

A 100 mm base module (M) with multi-modules such as 3M, 6M and 12M governs sizes of components, furniture grids and building layouts.

Prototyping sequence in design

Dimensioned orthographic views, then axonometric for spatial verification, then scale model, then full-size mock-up for ergonomic and material testing.