Drawing and Sketching: Line, Form, Perspective and Shading
Line and constructed form
Good drawing begins with construction, not outline. Block the subject with simple volumes - cube, sphere, cylinder, cone - then refine. A cylinder is drawn as two ellipses joined by straight sides; the ellipse opens as it approaches eye level and closes to a line at eye level. Contour lines describe edges; cross-contour lines describe surface curvature.
Perspective rules
- The horizon line is the viewer's eye level; it moves up or down with the viewpoint, never with the object.
- All vanishing points (VPs) for horizontal receding edges lie on the horizon line.
- One-point: front face parallel to the picture plane, one VP. Two-point: a corner faces the viewer, two VPs, verticals stay vertical. Three-point: looking up or down, so verticals also converge.
- Objects shrink and edges converge with distance; overlapping, placement and diminishing detail reinforce depth.
- Atmospheric perspective: distant forms lose contrast, cool in hue and soften in edge.
- Foreshortening: a form pointing towards the viewer appears shortened and overlaps itself.
Shading logic
Fix one light source, then place, in order: highlight, half-tone (mid-tone), core shadow, reflected light, cast shadow. Techniques - hatching, cross-hatching, stippling, blending, scumbling - each produce a different texture, but all must respect the same tonal order.
Worked example
A tea chest drawn corner-on: the receding top edges run to a VP on the left, the other receding edges to a VP on the right, both on the horizon. Reasoning: because two sets of horizontals recede, the drawing is two-point, not one-point; all vertical edges remain vertical because the viewer is not looking up.
Traps that cost marks
Putting a VP off the horizon; mixing one-point and two-point logic in one object; shading with pure black instead of a dark tone within the value range; cast shadow pointing towards the light; forgetting the reflected light that keeps shadow interiors readable.