Co far we have been dealing with drawing as applied to outline, and with the pictorial representation of an object in two dimensions, length and breadth. We now come to one of the greatest difficulties the beginner in drawing or painting has to face, namely, the third dimension; in other words, how to represent on a flat surface the appearance of thickness or depth back from the eye; for the two eyes, being stereoscopic, see partly round the object viewed, if it is not too large.
This representation in drawing is partly done by being able to set. out the first two dimensions accurately, while the third must be suggested by what we call "shading." Light is the great revealer of form in this direction, and to appreciate the full effect of the roundness or depth of an object the light must be concentrated on it. The more concentrated the light, the easier it will be to study the relative brightness or darkness of the planes that go to make up the object in vision.
The Destruction of Paganism
Up to the time of Cimabue and Giotto, art all over the world was governed by conventions which had been discovered and per-fected, and even lost again, by the artists of civilisations where life was easy and mostly in the open air; and where works of art also could be exposed and viewed out of doors.
After the destruction of pagan civilisation, the Christian Church became the chief patron and preserver of such artistic traditions as had survived; and controlled by the great Byzantine craftsmen in Constantinople, art in Europe for long hesitated in the course it should follow under the Renaissance taking place with more settled conditions of life.
The Story of a Dog
For good or for ill, the ideal of the "window" finally overcame, in the West, the old tradition that the "flatness of the wall must not be disturbed by the decoration on it." Whatever may be said from the point of view of the decorator, there is no doubt that the change threw open a vast field for intellectual experiment, and the world of art is much the richer for it. So, from the fifteenth century onwards, we have artists in the West mainly occupied with the various problems arising out of the representation of solidity and roundness on a flat surface by light and shade, and with the illusion of reality thereby obtained; in fact, the history of painting from then to the present day is the history of the third dimension.
No doubt the ancient Greeks had discovered it, but, probably from lack of a sufficiently perfect vehicle of expression, did not carry their study to completion, or we should have seen more signs of it in the polychrome vases, which present the nearest aspect to paintings, as we know them, of anything that has come down from the great Greek period. For their expression of the third dimension it is more likely that they relied on sculpture and some form of bas relief, in the handling of the materials for which they were masters. Much the same argument holds good in regard to Graeco-roman painting.
In Pompeii there are plenty of traces of study in the direction of giving the illusion of reality, but the achievement, apart from a sense of grace in drawing and design, is disappointing and unconvincing. Nowhere is there a deliberately studied cast shadow. One might expect signs of the existence of some such primitive master as Man-tegna, for instance; who, it is well known, was greatly influenced in his work by the study of such fragments of the antique as had been unearthed in his time. But there are none. It is true, however, that much of their painting had the appearance of a bas relief, which he also affected. There are those who may disagree with me here, relying on various stories that have come down, of the realism of paintings by Apelles, Xeuxis, and others; such as that tale of the birds pecking at a fruit piece. But such stories are common to all periods of art, and are for popular consumption.
I have never known a dog run up to the painted representation of another as he will to his own image in the looking-glass; and the most convincing story of this kind I have heard is that of the portrait painter who assured a dissatisfied sitter that he was certain that her pet dog would recognise the likeness. When the animal was introduced, it ran quickly up to the portrait, a full length one; and, to the astonishment of all, began jumping up and licking the dress quite eagerly. The painter afterwards gave away his "show" by telling how, alarmed at the rashness of his wager, he had smeared the bottom of the portrait with a thin coating of lard.
Painting, after all, is an intellectual process, and it is necessary to have some education in the means of expression to understand it. There are still tribes (I had nearly said people) of quite a high civilisation who cannot understand a drawing or photograph in two dimensions, but want to look round the back of the paper to see the other side.
To return to our history. I have a strong suspicion that the attention of artists of the Renaissance was largely attracted to the study of light and shade by the small windows, placed usually rather high up, which were prevalent in most houses and castles of the period. This forced the attention of the onlookers on the extreme effect of roundness and solidity produced by the concentration of the light.