No. 227. Method of obtaining a Segment of one-fifth of Vase.
If other divisions than those deducible from three or six are required, it will be necessary to draw also the plan curves from which the division can be obtained. Assuming that the elevation has been vertically divided as before, and the plan to be circular, a circle should be struck which is to represent the largest diameter and its circumference divided into the required number of parts. Lines are then drawn through to the centre. On the same centre other circles are struck with radii equal to the remaining horizontals, and each identified with the corresponding number or letter. The heights are obtained as before, and the diameters of the variations in the curvature can be ascertained by measuring round each of the plan curves in succession.
In the case of the plan being other than circular, the same rules apply, but the different plans would have to be drawn in each individual example.
Owing to the effect of perspective on rounded shapes, it is undesirable to employ the human figure, unless in bold relief, and then only on straight or slightly curved profiles.
CHAPTER VI
DEVELOPMENT OF CONVENTIONAL ORNAMENT
THE term Convention is applied to decoration in which there is distinct evidence of artistic restraint, which may be purely æsthetic or due to technical conditions.
Outline Drawing
The rendering of any form in outline is probably the simplest form of convention, which is generally accepted through tradition as representation. Though the objects so depicted really depend on light, shade, and local colour for their appearance.
Such outline drawings may be in other respects realistic, but a further degree of convention is the desirable elimination of perspective where it is unsuitable to the effect desired. For instance, in silhouette, profile renderings only are intelligible, and in delicate bas-relief modelling any foreshortening should be avoided if confusing to the effect.
In direct personal work, such as drawing or painting, when craft conditions other than that of the medium employed are not involved, convention is purely a matter of discretion and consideration of the nature and object of the work; but it is essential in design when the material and method of production have to be considered. In painting the artist may employ the full resources of his palette and be as realistic in his effect as is in his power, but if the purpose be mural decoration restraint is at once imposed.