Punjab PSEB Matric Mechanical Drawing and Painting cheat sheet

Standard sheet sizes (ISO A series): A0 = 841 × 1189 mm; each lower number is the previous size halved on the longer side, so A1 = 594 × 841 mm, A2 = 420 × 594 mm, A3 = 297 × 420 mm, A4 = 210 × 297 mm.

Pencil grades run 9H (hardest, lightest) through H, F, HB, B to 9B (softest, blackest); H and 2H are used for construction and dimension lines, HB for lettering and freehand work, 2B to 4B for shading and object drawing.

A T-square is used only against a true drawing-board edge: the stock is held against the left edge of the board and the blade gives horizontal lines; set squares (45° and 30°–60°) resting on the blade give verticals and 30°, 45°, 60° and 15° multiples.

A French curve is used for irregular curves by fitting it to at least three plotted points at a time and joining successive short arcs; a compass draws circles, a bow compass small circles, and dividers only transfer or divide distances.

The title block is placed at the bottom right of the sheet and carries drawing number, title, scale, sheet size, material, date, and the draughtsman's and checker's names; it is read from the bottom edge of the sheet.

Preferred scales are 1:1, 1:2, 1:5, 1:10, 1:20, 1:50, 1:100, 1:200, 1:500, 1:1000 (reducing) and 2:1, 5:1, 10:1 (enlarging); a representative fraction (RF) = drawing length ÷ actual length, and a scale is written as RF followed by the unit.

Line conventions: continuous thick (0.5–0.7 mm) for visible outlines; continuous thin for dimension, extension, leader and hatching lines; short dashes for hidden edges; long-dash-dot thin for centre lines and axes; continuous thin with zigzag for cutting-plane lines.

A drawing instrument set is kept true by graphite of correct grade, by never sharpening a compass lead to a knife point (it is chisel-pointed), and by cleaning the board and instruments before use so that graphite does not smear the sheet.

IS 9609 / IS 696 style single-stroke italic capitals are the standard drawing lettering: height h of capitals, lowercase height about 0.7h, stroke width about h/14 for style A and h/10 for style B; minimum lettering height on drawings is 2.5 mm, with 3.5, 5, 7, 10 and 14 mm as preferred sizes.

Lettering is drawn between faint guide lines; the ratio of height to width for standard capitals is about 1:0.7, spacing between letters about one-fifth of the letter height, and spacing between words equal to about one letter width.

A dimension consists of the dimension line (thin, continuous, terminated by arrowheads), extension lines (thin, starting about 1 mm clear of the object and extending about 2–3 mm beyond the dimension line), and the numeral placed above and parallel to the dimension line, readable from the bottom or right-hand edge.

Arrowheads are about 3 mm long and one-third as wide; where space is too small for arrows, they are placed outside the extension lines and the dimension line is extended, or a dot/slash termination is used.

Diameter is prefixed Ø, radius R, spherical radius SR, spherical diameter SØ, square section □, and a 45° chamfer is written as 2 × 45°; a dimension with a tolerance is written as 40 +0.05/−0.02 or 40 ± 0.1.

Rules of dimensioning: dimension each feature once only, never dimension a dimension, place dimensions outside the view where possible, group them in rows, and avoid crossing dimension lines with extension lines or with each other.

Angular dimensions use a thin arc as the dimension line with the numeral written horizontally or aligned with the arc; angles are given in degrees, minutes and seconds (e.g. 30° 15′).

Hidden lines are drawn with short dashes of about 3 mm with 1 mm gaps and must touch the outlines they meet; centre lines extend 2–3 mm beyond the circle and are drawn as long dash, short dash, long dash, with the long dash about 20 mm.

Hatching for a section is continuous thin lines at 45° to the axis, spaced 2–4 mm uniformly; adjacent parts are hatched in opposite directions or at different spacings.

First-angle projection (the IS convention) places the object between the observer and the plane, so the view from the front is drawn above the plan and the view from the left is drawn on the right; third-angle projection reverses these positions and is marked by the truncated-cone symbol.

The principal planes are the vertical plane (VP) and horizontal plane (HP), meeting in the XY reference line; a point's front view lies on the VP and its top view on the HP, both projected to the same projector perpendicular to XY.

A point in the first quadrant has its front view above XY and its top view below XY; the distance of the front view from XY equals the height above HP, and the distance of the top view from XY equals the distance in front of VP.

A point on the HP has its top view on XY; a point on the VP has its front view on XY; a point on both planes has both views on XY; a point in the second quadrant has both views above XY.

A line parallel to both HP and VP shows true length in both front and top views; a line parallel to HP and inclined to VP shows true length in the top view and appears inclined in the front view; the reverse holds for a line parallel to VP and inclined to HP.

A line inclined to both planes is solved by the rotating-line method: draw the line parallel to one plane to get true length and true inclination, then rotate to the required position and project the final views; the true length is found from a right triangle whose base is the plan length and height the difference of elevations.

The true inclination of a line to the HP appears only in the view where the line is parallel to the VP; apparent inclinations in other views are always smaller than the true inclination.

A plane surface appears as an edge view (a line) when it is perpendicular to one reference plane and inclined to the other, and as true shape only when it is parallel to a reference plane.

Traces: the horizontal trace (HT) is where the line or plane meets the HP and the vertical trace (VT) where it meets the VP; a line parallel to HP has no HT, and a line parallel to VP has no VT.

Solids are classified as polyhedra (prism, pyramid, cube, tetrahedron) bounded by plane faces, and solids of revolution (cylinder, cone, sphere) bounded by curved surfaces; a prism has two parallel polygonal bases, a pyramid one base and triangular faces meeting at an apex.

In first-angle projection of a solid, the top view is drawn first when the axis is vertical: a vertical cylinder gives a circle in plan and a rectangle in elevation; a vertical cone gives a circle with the apex at its centre in plan and a triangle in elevation.

The axis of a solid is shown by a long-dash-dot centre line extending 2–3 mm beyond the outline in both views; hidden edges of a solid are shown dashed only where they are not visible in that view.

A right regular pentagonal prism resting on its base on HP shows a true pentagon in plan; when resting on one base edge inclined to VP, the plan is rotated so the edge makes the given angle with XY and the elevation is built from the plan.

A solid resting on HP on a corner, or with its axis inclined to HP, is solved by projecting the solid in the simple position first, then tilting the elevation to the required angle and projecting the final plan from it.

A section plane is shown in the view where it appears as an edge by a cutting-plane line (long dash, short dash, long dash, thin, with arrows at the ends showing the direction of sight) and labelled with capital letters at the ends.

A sectional view shows the cut surface hatched at 45° and omits all hidden lines behind the plane; visible edges beyond the plane are drawn as full lines, and the section is named SECTIONAL PLAN or SECTIONAL ELEVATION.

A true shape of section is obtained only when the section plane is parallel to the plane of projection; otherwise the section is drawn in the auxiliary view on a plane parallel to the section plane.

A frustum is the portion of a solid between its base and a section plane parallel to the base; a truncated solid has the cut surface inclined to the base, and its true shape is found by an auxiliary view.

Isometric projection uses three axes at 120° to each other, with the vertical axis at 90° and the two receding axes at 30° above the horizontal; the three axes make equal angles with the plane of projection, so all three are equally foreshortened.

In true isometric projection every edge is foreshortened by the factor 0.816; in isometric drawing (the common practice) full lengths are set off along the isometric axes, giving a drawing 1/0.816 = 1.22 times the true projection.

Isometric lines are lines parallel to the three isometric axes and are the only lines whose lengths can be measured directly; non-isometric lines are located by their end points, and angles are never measured but constructed from coordinates.

A circle in isometric appears as an ellipse; in isometric drawing the ellipse has a major axis 1.22 × the true diameter and a minor axis 0.71 × the true diameter, with the major axis perpendicular to the axis of the cylinder.

The four-centre method draws an isometric ellipse from a circumscribing rhombus by striking four arcs from the rhombus corners and the intersections of diagonals with the centre lines; it is an approximation, exact only at the four tangent points.

In cavalier oblique projection the receding axis is drawn at full scale (usually 45°, sometimes 30° or 60°); in cabinet oblique the receding axis is drawn at half scale to reduce distortion; the front face is always drawn true shape and size.

Oblique projection shows the true shape of the face parallel to the plane of projection, so it suits objects with one complex face; isometric projection shows all three faces equally and suits objects whose faces are all simple.

Isometric drawing procedure: set the three axes, mark overall dimensions along them, draw only isometric lines, then locate non-isometric points by offsets parallel to the axes, and finally darken visible edges and omit hidden lines.

Development is the true shape of a surface unfolded onto a plane; it is possible only for developable surfaces - polyhedra, cylinders and cones - and impossible for double-curved surfaces such as the sphere, which is approximated by zones or lunes.

Parallel-line development is used for prisms and cylinders: divide the base circle or perimeter into equal parts, set them out along a straight line equal to the perimeter (πD for a cylinder), and erect perpendiculars of height equal to the solid's height.

Radial-line development is used for pyramids and cones: draw the true length of the slant edge or generator as radius, step off the base divisions along the arc, and join to the apex; for a cone the sector angle is 360° × r / L, where r is the base radius and L the slant height.

Triangulation development is used for oblique and transitional pieces such as a square-to-round duct: divide the surface into triangles, find the true length of each side by the right-triangle method, then build the triangles in sequence.

The true length of a slant edge is found by constructing a right triangle with the plan length as base and the difference in height as altitude; the hypotenuse is the true length.

The development of a truncated cylinder is a rectangle with an irregular curve at the cut end, obtained by projecting the cut points from the elevation onto the corresponding generators of the development.

A curve of intersection (interpenetration curve) is drawn by locating points common to both surfaces: take a series of cutting planes, find where each plane cuts each solid, and mark the points where those cut lines meet.

When two cylinders of equal diameter intersect at right angles, the curve of intersection is two straight lines crossing at the centre, forming a cross in the elevation; unequal diameters give a curve bending towards the axis of the smaller cylinder.

In development drawings, the seam is placed on the shortest generator to save material, and bend lines are shown as thin continuous lines while the outline is thick.

Freehand sketching uses the same projection rules as instrumental drawing but relies on proportion, not scale: overall height is fixed first, then width compared against it, then subdivisions judged by eye against the whole.

Straight freehand lines are drawn from the shoulder with the eye on the end point, not on the pencil; long lines are drawn in short overlapping strokes, and a light construction box is drawn first for any object.

Freehand circles are drawn from a light square or from centre lines, marking the four tangent points and joining them with arcs; ellipses are enclosed in a parallelogram whose sides touch the ellipse at the mid-points.

In object drawing, the object is first enclosed in a bounding box or a simple geometric solid (box, cylinder, sphere), and the parts are then cut out of that envelope; all construction lines stay light and only the final outline is darkened.

Proportion is checked by the pencil-sight method: hold the pencil at arm's length, measure one dimension against another on the pencil, and transfer that ratio to the paper; never measure the object and the drawing at the same distance.

Ellipses obey perspective: the ellipse's minor axis always points towards the vanishing point of the axis of the cylinder, and the ellipse becomes narrower (more closed) as the circle approaches eye level.

Shading in object drawing follows a consistent light source: the side facing the light is left lightest, the side away is darkest, and a reflected light appears along the shadow edge; cast shadows are darkest close to the object.

Line quality distinguishes drawing types: outlines are firm and continuous, construction lines light and broken, and shading lines follow the form of the surface rather than a fixed direction.

Primary colours are red, yellow and blue in pigment theory; secondaries are made by mixing two primaries (orange, green, violet), and tertiaries by mixing a primary with an adjacent secondary.

Complementary pairs are red–green, yellow–violet and blue–orange; placed side by side they intensify each other, and mixed together they neutralise towards grey or brown.

Colour has three attributes: hue (the name), value or tone (lightness to darkness) and intensity or saturation (purity); a tint is made by adding white and a shade by adding black.

Warm colours (red, orange, yellow) appear to advance and cool colours (blue, green, violet) to recede, which is used to create depth in landscape and still life.

Watercolour is transparent: light comes from the white paper, so colours are laid in thin washes from light to dark, and white is never used as an opaque body colour; wet-in-wet gives soft edges and wet-on-dry gives crisp edges.

Poster or tempera colour is opaque and can be laid light over dark; it is mixed to a creamy consistency and applied in flat areas, with the darker tones laid first and the lighter ones last.

Oil paint is worked fat over lean (more oil in each successive layer) to prevent cracking, is blended on the canvas while wet, and dries slowly; acrylic dries fast, thins with water and darkens slightly on drying.

Brushes: flat brushes lay washes and block in shapes, round brushes make lines and detail, and a dry brush on a dry surface gives broken texture; the brush is held lightly near the ferrule for detail and further up the handle for broad strokes.

A limited palette of about six colours plus white is mixed on the palette from light to dark, and each mixture is tested on the painting edge before it is applied to the work.

The rule of thirds places the centre of interest near one of the four intersections of lines dividing the picture into thirds; placing the subject exactly at the centre or exactly on the edge makes a static or unstable composition.

A composition needs a focal point, a path for the eye (leading lines, repeated shapes, edges of tone), and balance; balance may be symmetrical (formal) or asymmetrical (informal, balanced by tone or size rather than by count).

Overlapping shapes give depth, and atmospheric perspective makes distant objects lighter, cooler, less detailed and lower in contrast than foreground objects.

In still life the group is arranged so that objects overlap and vary in height, size and shape, with the tallest object off-centre; a single light source from one side gives consistent shadows and a clear light-and-dark pattern.

The horizon line in a still life or interior lies at the eye level of the viewer; all receding horizontal edges converge to a vanishing point on that line, and objects below eye level show their top surfaces.

A thumbnail sketch of three or four values (light, mid-light, mid-dark, dark) is planned before painting; keeping the darkest dark and lightest light adjacent at the focal point gives the strongest effect.

In nature study, leaves are drawn from the stem outward with a central midrib and branching veins, and the characteristic silhouette, margin (entire, serrated, lobed) and venation are recorded before colour is added.

Colour in landscape follows aerial perspective and time of day: early morning and evening light is warm and casts long shadows, midday light is cooler and shadows are short, and shadows take the complementary colour of the light.

A finished composition is judged by unity, harmony, rhythm and dominance: one element (tone, colour or shape) should dominate, and every part should relate to the focal point rather than compete with it.

Standard sheet sizes (ISO A series): A0 = 841 × 1189 mm; each lower number is the previous size halved on the longer side, so A1 = 594 × 841 mm, A2 = 420 × 594 mm, A3 = 297 × 420 mm, A4 = 210 × 297 mm.

Pencil grades run 9H (hardest, lightest) through H, F, HB, B to 9B (softest, blackest); H and 2H are used for construction and dimension lines, HB for lettering and freehand work, 2B to 4B for shading and object drawing.

A T-square is used only against a true drawing-board edge: the stock is held against the left edge of the board and the blade gives horizontal lines; set squares (45° and 30°–60°) resting on the blade give verticals and 30°, 45°, 60° and 15° multiples.

A French curve is used for irregular curves by fitting it to at least three plotted points at a time and joining successive short arcs; a compass draws circles, a bow compass small circles, and dividers only transfer or divide distances.

The title block is placed at the bottom right of the sheet and carries drawing number, title, scale, sheet size, material, date, and the draughtsman's and checker's names; it is read from the bottom edge of the sheet.

Preferred scales are 1:1, 1:2, 1:5, 1:10, 1:20, 1:50, 1:100, 1:200, 1:500, 1:1000 (reducing) and 2:1, 5:1, 10:1 (enlarging); a representative fraction (RF) = drawing length ÷ actual length, and a scale is written as RF followed by the unit.

Line conventions: continuous thick (0.5–0.7 mm) for visible outlines; continuous thin for dimension, extension, leader and hatching lines; short dashes for hidden edges; long-dash-dot thin for centre lines and axes; continuous thin with zigzag for cutting-plane lines.

A drawing instrument set is kept true by graphite of correct grade, by never sharpening a compass lead to a knife point (it is chisel-pointed), and by cleaning the board and instruments before use so that graphite does not smear the sheet.

IS 9609 / IS 696 style single-stroke italic capitals are the standard drawing lettering: height h of capitals, lowercase height about 0.7h, stroke width about h/14 for style A and h/10 for style B; minimum lettering height on drawings is 2.5 mm, with 3.5, 5, 7, 10 and 14 mm as preferred sizes.

Lettering is drawn between faint guide lines; the ratio of height to width for standard capitals is about 1:0.7, spacing between letters about one-fifth of the letter height, and spacing between words equal to about one letter width.

A dimension consists of the dimension line (thin, continuous, terminated by arrowheads), extension lines (thin, starting about 1 mm clear of the object and extending about 2–3 mm beyond the dimension line), and the numeral placed above and parallel to the dimension line, readable from the bottom or right-hand edge.

Arrowheads are about 3 mm long and one-third as wide; where space is too small for arrows, they are placed outside the extension lines and the dimension line is extended, or a dot/slash termination is used.

Diameter is prefixed Ø, radius R, spherical radius SR, spherical diameter SØ, square section □, and a 45° chamfer is written as 2 × 45°; a dimension with a tolerance is written as 40 +0.05/−0.02 or 40 ± 0.1.

Rules of dimensioning: dimension each feature once only, never dimension a dimension, place dimensions outside the view where possible, group them in rows, and avoid crossing dimension lines with extension lines or with each other.

Angular dimensions use a thin arc as the dimension line with the numeral written horizontally or aligned with the arc; angles are given in degrees, minutes and seconds (e.g. 30° 15′).

Hidden lines are drawn with short dashes of about 3 mm with 1 mm gaps and must touch the outlines they meet; centre lines extend 2–3 mm beyond the circle and are drawn as long dash, short dash, long dash, with the long dash about 20 mm.

Hatching for a section is continuous thin lines at 45° to the axis, spaced 2–4 mm uniformly; adjacent parts are hatched in opposite directions or at different spacings.

First-angle projection (the IS convention) places the object between the observer and the plane, so the view from the front is drawn above the plan and the view from the left is drawn on the right; third-angle projection reverses these positions and is marked by the truncated-cone symbol.

The principal planes are the vertical plane (VP) and horizontal plane (HP), meeting in the XY reference line; a point's front view lies on the VP and its top view on the HP, both projected to the same projector perpendicular to XY.

A point in the first quadrant has its front view above XY and its top view below XY; the distance of the front view from XY equals the height above HP, and the distance of the top view from XY equals the distance in front of VP.

A point on the HP has its top view on XY; a point on the VP has its front view on XY; a point on both planes has both views on XY; a point in the second quadrant has both views above XY.

A line parallel to both HP and VP shows true length in both front and top views; a line parallel to HP and inclined to VP shows true length in the top view and appears inclined in the front view; the reverse holds for a line parallel to VP and inclined to HP.

A line inclined to both planes is solved by the rotating-line method: draw the line parallel to one plane to get true length and true inclination, then rotate to the required position and project the final views; the true length is found from a right triangle whose base is the plan length and height the difference of elevations.

The true inclination of a line to the HP appears only in the view where the line is parallel to the VP; apparent inclinations in other views are always smaller than the true inclination.

A plane surface appears as an edge view (a line) when it is perpendicular to one reference plane and inclined to the other, and as true shape only when it is parallel to a reference plane.

Traces: the horizontal trace (HT) is where the line or plane meets the HP and the vertical trace (VT) where it meets the VP; a line parallel to HP has no HT, and a line parallel to VP has no VT.

Solids are classified as polyhedra (prism, pyramid, cube, tetrahedron) bounded by plane faces, and solids of revolution (cylinder, cone, sphere) bounded by curved surfaces; a prism has two parallel polygonal bases, a pyramid one base and triangular faces meeting at an apex.

In first-angle projection of a solid, the top view is drawn first when the axis is vertical: a vertical cylinder gives a circle in plan and a rectangle in elevation; a vertical cone gives a circle with the apex at its centre in plan and a triangle in elevation.

The axis of a solid is shown by a long-dash-dot centre line extending 2–3 mm beyond the outline in both views; hidden edges of a solid are shown dashed only where they are not visible in that view.

A right regular pentagonal prism resting on its base on HP shows a true pentagon in plan; when resting on one base edge inclined to VP, the plan is rotated so the edge makes the given angle with XY and the elevation is built from the plan.

A solid resting on HP on a corner, or with its axis inclined to HP, is solved by projecting the solid in the simple position first, then tilting the elevation to the required angle and projecting the final plan from it.

A section plane is shown in the view where it appears as an edge by a cutting-plane line (long dash, short dash, long dash, thin, with arrows at the ends showing the direction of sight) and labelled with capital letters at the ends.

A sectional view shows the cut surface hatched at 45° and omits all hidden lines behind the plane; visible edges beyond the plane are drawn as full lines, and the section is named SECTIONAL PLAN or SECTIONAL ELEVATION.

A true shape of section is obtained only when the section plane is parallel to the plane of projection; otherwise the section is drawn in the auxiliary view on a plane parallel to the section plane.

A frustum is the portion of a solid between its base and a section plane parallel to the base; a truncated solid has the cut surface inclined to the base, and its true shape is found by an auxiliary view.

Isometric projection uses three axes at 120° to each other, with the vertical axis at 90° and the two receding axes at 30° above the horizontal; the three axes make equal angles with the plane of projection, so all three are equally foreshortened.

In true isometric projection every edge is foreshortened by the factor 0.816; in isometric drawing (the common practice) full lengths are set off along the isometric axes, giving a drawing 1/0.816 = 1.22 times the true projection.

Isometric lines are lines parallel to the three isometric axes and are the only lines whose lengths can be measured directly; non-isometric lines are located by their end points, and angles are never measured but constructed from coordinates.

A circle in isometric appears as an ellipse; in isometric drawing the ellipse has a major axis 1.22 × the true diameter and a minor axis 0.71 × the true diameter, with the major axis perpendicular to the axis of the cylinder.

The four-centre method draws an isometric ellipse from a circumscribing rhombus by striking four arcs from the rhombus corners and the intersections of diagonals with the centre lines; it is an approximation, exact only at the four tangent points.

In cavalier oblique projection the receding axis is drawn at full scale (usually 45°, sometimes 30° or 60°); in cabinet oblique the receding axis is drawn at half scale to reduce distortion; the front face is always drawn true shape and size.

Oblique projection shows the true shape of the face parallel to the plane of projection, so it suits objects with one complex face; isometric projection shows all three faces equally and suits objects whose faces are all simple.

Isometric drawing procedure: set the three axes, mark overall dimensions along them, draw only isometric lines, then locate non-isometric points by offsets parallel to the axes, and finally darken visible edges and omit hidden lines.

Development is the true shape of a surface unfolded onto a plane; it is possible only for developable surfaces - polyhedra, cylinders and cones - and impossible for double-curved surfaces such as the sphere, which is approximated by zones or lunes.

Parallel-line development is used for prisms and cylinders: divide the base circle or perimeter into equal parts, set them out along a straight line equal to the perimeter (πD for a cylinder), and erect perpendiculars of height equal to the solid's height.

Radial-line development is used for pyramids and cones: draw the true length of the slant edge or generator as radius, step off the base divisions along the arc, and join to the apex; for a cone the sector angle is 360° × r / L, where r is the base radius and L the slant height.

Triangulation development is used for oblique and transitional pieces such as a square-to-round duct: divide the surface into triangles, find the true length of each side by the right-triangle method, then build the triangles in sequence.

The true length of a slant edge is found by constructing a right triangle with the plan length as base and the difference in height as altitude; the hypotenuse is the true length.

The development of a truncated cylinder is a rectangle with an irregular curve at the cut end, obtained by projecting the cut points from the elevation onto the corresponding generators of the development.

A curve of intersection (interpenetration curve) is drawn by locating points common to both surfaces: take a series of cutting planes, find where each plane cuts each solid, and mark the points where those cut lines meet.

When two cylinders of equal diameter intersect at right angles, the curve of intersection is two straight lines crossing at the centre, forming a cross in the elevation; unequal diameters give a curve bending towards the axis of the smaller cylinder.

In development drawings, the seam is placed on the shortest generator to save material, and bend lines are shown as thin continuous lines while the outline is thick.

Freehand sketching uses the same projection rules as instrumental drawing but relies on proportion, not scale: overall height is fixed first, then width compared against it, then subdivisions judged by eye against the whole.

Straight freehand lines are drawn from the shoulder with the eye on the end point, not on the pencil; long lines are drawn in short overlapping strokes, and a light construction box is drawn first for any object.

Freehand circles are drawn from a light square or from centre lines, marking the four tangent points and joining them with arcs; ellipses are enclosed in a parallelogram whose sides touch the ellipse at the mid-points.

In object drawing, the object is first enclosed in a bounding box or a simple geometric solid (box, cylinder, sphere), and the parts are then cut out of that envelope; all construction lines stay light and only the final outline is darkened.

Proportion is checked by the pencil-sight method: hold the pencil at arm's length, measure one dimension against another on the pencil, and transfer that ratio to the paper; never measure the object and the drawing at the same distance.

Ellipses obey perspective: the ellipse's minor axis always points towards the vanishing point of the axis of the cylinder, and the ellipse becomes narrower (more closed) as the circle approaches eye level.

Shading in object drawing follows a consistent light source: the side facing the light is left lightest, the side away is darkest, and a reflected light appears along the shadow edge; cast shadows are darkest close to the object.

Line quality distinguishes drawing types: outlines are firm and continuous, construction lines light and broken, and shading lines follow the form of the surface rather than a fixed direction.

Primary colours are red, yellow and blue in pigment theory; secondaries are made by mixing two primaries (orange, green, violet), and tertiaries by mixing a primary with an adjacent secondary.

Complementary pairs are red–green, yellow–violet and blue–orange; placed side by side they intensify each other, and mixed together they neutralise towards grey or brown.

Colour has three attributes: hue (the name), value or tone (lightness to darkness) and intensity or saturation (purity); a tint is made by adding white and a shade by adding black.

Warm colours (red, orange, yellow) appear to advance and cool colours (blue, green, violet) to recede, which is used to create depth in landscape and still life.

Watercolour is transparent: light comes from the white paper, so colours are laid in thin washes from light to dark, and white is never used as an opaque body colour; wet-in-wet gives soft edges and wet-on-dry gives crisp edges.

Poster or tempera colour is opaque and can be laid light over dark; it is mixed to a creamy consistency and applied in flat areas, with the darker tones laid first and the lighter ones last.

Oil paint is worked fat over lean (more oil in each successive layer) to prevent cracking, is blended on the canvas while wet, and dries slowly; acrylic dries fast, thins with water and darkens slightly on drying.

Brushes: flat brushes lay washes and block in shapes, round brushes make lines and detail, and a dry brush on a dry surface gives broken texture; the brush is held lightly near the ferrule for detail and further up the handle for broad strokes.

A limited palette of about six colours plus white is mixed on the palette from light to dark, and each mixture is tested on the painting edge before it is applied to the work.

The rule of thirds places the centre of interest near one of the four intersections of lines dividing the picture into thirds; placing the subject exactly at the centre or exactly on the edge makes a static or unstable composition.

A composition needs a focal point, a path for the eye (leading lines, repeated shapes, edges of tone), and balance; balance may be symmetrical (formal) or asymmetrical (informal, balanced by tone or size rather than by count).

Overlapping shapes give depth, and atmospheric perspective makes distant objects lighter, cooler, less detailed and lower in contrast than foreground objects.

In still life the group is arranged so that objects overlap and vary in height, size and shape, with the tallest object off-centre; a single light source from one side gives consistent shadows and a clear light-and-dark pattern.

The horizon line in a still life or interior lies at the eye level of the viewer; all receding horizontal edges converge to a vanishing point on that line, and objects below eye level show their top surfaces.

A thumbnail sketch of three or four values (light, mid-light, mid-dark, dark) is planned before painting; keeping the darkest dark and lightest light adjacent at the focal point gives the strongest effect.

In nature study, leaves are drawn from the stem outward with a central midrib and branching veins, and the characteristic silhouette, margin (entire, serrated, lobed) and venation are recorded before colour is added.

Colour in landscape follows aerial perspective and time of day: early morning and evening light is warm and casts long shadows, midday light is cooler and shadows are short, and shadows take the complementary colour of the light.

A finished composition is judged by unity, harmony, rhythm and dominance: one element (tone, colour or shape) should dominate, and every part should relate to the focal point rather than compete with it.