Colour dynamics: visual perception and illusion

Our perception of shape and form can also play optical tricks on our understanding of a building form. For example, this illustration shows two different cladding profiles next to each other, facing the viewer. From the information presented, there is no way that we can know which parts of the profile project towards us and which project away from us, in fact, the profile on the left has wide ribs projecting towards us and narrow troughs projecting away from us; the cladding profile on the right is just the reverse of this.

Optical illusions are diminished on cladding when shadows are introduced and when the shadow-casting element is in evidence.

However, when shadows occur and sight of the shadow-casting element is introduced, the optical illusion is diminished and our understanding of the plane is clarified. Consequently, to reduce visual ambiguity in building design, ensure the presence of such shadows.

The pattern of ribs in cladding function to bring scale to a building, but their direction can distort our perception of the shape of a plane.

An important visual function of the pattern of ribs in cladding is the perceptual reduction of a large plane to that of human scale. However, the direction of ribs can also influence the perceived shape of a building. For instance, the three identical squares shown here appear unequal because each of the divided planes seem to occupy a larger area than the undivided plane. The directional orientation of the ribs further distorts the proportions of the original square, i.e. horizontal ribs making the middle square appear wider, while the vertical ribs cause the square on the right to appear taller.