Form, Volume and Three-Dimensional Modeling
Examiners use this domain to decide whether your objects are solid or merely outlined. A modelled drawing shows thickness: a top and a bottom, a front and a receding side, and a consistent logic of how surfaces turn. The test is not shading density; it is whether a viewer could rotate the object in their mind.
Reduce to primitive volumes
- Every object is a box, cylinder, sphere or cone, modified. Draw the volume first, then the modifications: the handle is a torus section, the spout a small cone.
- A box in three-quarter view shows three faces; each face is a distinct value plane even before shading.
- A cylinder has a top ellipse, two straight sides and a bottom ellipse, and both ellipses share one axis.
Cross-contours and the turning surface
- Cross-contour lines wrap around the form; where they bunch together the surface is turning away from you, where they spread it faces you.
- The silhouette alone is not enough: a sphere and a flat disc share the same outline. Only the interior turning lines separate them.
Edges
- Near edges are sharp and slightly darker; far edges soften. This hierarchy alone creates depth without any shading at all.
Worked example
Three objects: a plaster sphere, a cube and a folded cloth. Model the sphere with no hard edges - its terminator is itself an ellipse - and place three or four light cross-contours across it to prove it is round. Give the cube three faces, three values, and make its front vertical edge the strongest accent. Model the cloth as alternating planes: convex folds catch light, concave valleys go dark, and the folds must behave like bent card, not fur. Check: if all the tone were removed, the remaining lines should still describe volume.
Traps
- Outlining and filling in, which produces a coloured silhouette.
- Drawing only the front face and forgetting the top plane of a box.
- Tilted or pointed ellipses on bottles and cans that contradict the object's axis.
- Modelling the background object so heavily that it competes with the foreground.