In addition, he put the emphasis on the images' context and on the combination of object-parts. Some of his test subjects even used perspective distortion or occlusion. Two blind peoples' drawings showing a table. Only late blind people and those who had been taught drawing principles tried to draw perspective. To depict vessels, cross-sectional pictures were used.
Contour lines can show depths.
In many cases combinations of these four methods were used. 2 shows two examples. The drawing methods described here, have been generalised and used in a program described in the next section. Where is it and how is it constructed. Imagine that the whole object consisted of rubber.