2 -- Expression of three-dimensional effect 
         using colors and textures

 

(1) Effect of gradation (shading)

A three-dimensional shape has a variation in brightness by the way the light hits it even if the surface is painted uniformly using the same color. When light is shone on it, the brightness of each surface composing a solid is different when the solid has curved surfaces or concavities or even when it does not have any of them. Furthermore, the brightness is not uniform on each plane. It is easily understood if we prepare a solid model, and take a picture of it. 

In other words, each surface has a variation in the brightness respectively, and there exists the shape of a solid as an assembly of those surfaces. In order to describe an attractive solid, the elements of "shadow" and "variation of brightness" are important, as well as good shape.

When a plane or curved surface with a simple geometrical configuration is naturally placed and observed, it is understood that the brightness on the surface changes regularly and gradually. Therefore, we feel a three-dimensional effect on these artificial plane diagrams if a gradation of brightness is changing gradually from a bright area to a dark area. Illusions of a complex solid which do not exist in real three-dimensional space can be composed when the surfaces are drawn freely using this shading skill described above.
 
 


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410
 
411
412

 

Figure 409: Composition by dropping colors.
Figure 410: Expression of unevenness by gradation.
Figure 411: "Scenery with Arcs", by Ryoichi Horie.
Figure 412: Composition of a complicated cubic effect by gradation.


 

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