In terms of opportunities for visual composition in the natural world, circles occur less frequently than triangles. This is because the points which would imply a circle have much less freedom of position. Without the support of a curving edge or line, the composer would require:
- at least five points, because three points would be perceived as a triangle and four as a square;
- the points, and track of any curve, to be equally distant from a central point in space; and
- they would have to close enough to each other to provide perceptual closure.
Circles have an enclosing effect, tending to focus the eye inward towards their centre; therefore they are a powerful means of directing the viewer's attention into what they contain. There can also be a slight feeling movement along a circle's periphery which comes from its association with rotation.
Naturally-occurring circles include bubbles, the sun, the moon, and organisms featuring radial growth.
Ellipses, often interpreted as circles viewed at an angle, possess the same properties
i.e. feeling of enclosure, and direction of attention inward to a focal point. Unlike a circle, ellipses have only two axes of symmetry and they have greater dynamism because the speed of visual flow changes - accelerating or decelerating - along its periphery.
