Visual Grammar by Christian Leborg, pages 18 to 25.
Objects placed in a recognizable pattern have structure. If the structure lines are not visible, it is abstract, and abstract structures can be formal or informal.
Objects evenly distributed throughout a structure have formal structure. The objects may be equidistant from one another, or the placement of objects may occur according to an arithmetic or geometric progression. A good example of formal structure is a composition grid based on the rule of thirds. Non-repetitive structures such as gradation and radiation are also formal. Gradation means the “structure units change in size or form (or both) at an even rate” (20). In radiation, structure units “are situated around a common center” (21). Structures that have radiation can have centrifugal structure and/or concentric structure. Lines radiate out from a common center in centrifugal structure, and they are unequal in distance from the center in concentric structure. The author uses a spiral as an example of a structure that is both concentric and centrifugal.
A structure is informal if the viewer cannot perceive any pattern at all, or a pattern without implied straight lines. If the pattern of object placement is based on visual perception alone, it has visual distribution (aka similarity structure).
Even if a composition has only abstract structure, our brains complete the picture, so we still recognize the lines’ placement. Invisible structures can also have inactive structure, which means that while the structure tells us position, it has no effect on the objects’ form. Regardless of the type of structure – formal or informal, visible or invisible, active or inactive – all compositions have some type of structural skeleton.
Slideshare.net has an interesting discussion of visual structure by Palak Sanghani, designer, programmer, and avid blogger in India. Sanghani notes that all visual compositions have structure whether intentional or not, and that the structure “generally imposes order and predetermines internal relationships of forms in any visual.” She breaks structure down into three categories – formal, semi-formal, and informal – and then describes each.
Formal structures have structural lines constructed in a rigid, mathematical manner. In these structures, subdivisions of space are equal or rhythmical, and form organization has “a strong sense of regularity.” Formal structure includes repetition, gradation, and radiation. According to Sanghani, “a semi-formal structure is usually quite regular, but marginal irregularity exists,” and it may or may not have structural lines. An informal structure generally has indefinite organization and does not normally have structural lines.
Sanghani also discusses inactive and active structures and has an interesting way to differentiate. Like our textbook author, she notes that in inactive structures, structural lines guide the placement of unit forms, but do not interfere with their shape. She further notes, however, that in inactive structures, structural lines do not “divide the space up into distinct areas where color variations can be introduced as they do in active structures. Her blog also discusses the basic grid and its variations.
http://www.slideshare.net/PalakSanghani/structure-25011745#btnNext
http://www.slideshare.net/PalakSanghani/gradation#btnNext
http://www.slideshare.net/PalakSanghani/structure-25011745#btnNext
http://www.oswaldcompanies.com/expertise/financial-institutions/
The window panes of this skyscraper make up a structured grid. All of the windows are the same size and are equidistant from each other. The window sills between the glass panes can be thought of as the structure holding the panes together.
http://investment-fiduciary.com/2011/11/09/is-the-sky-clear-enough-yet/
At the horizon, the sky is very light, almost white even, but as viewer looks up towards the top of the image, the sky gradates to a darker shade of blue.
http://www.publicdomainpictures.net/view-image.php?image=297
This seashell displays a form of radiation. The spiral that makes up the shell starts with a small circle in the middle of the shell, but circles around, getting bigger with every revolution until the spiral meets the opening of the shell.
http://ssimplyme.com/28-uses-for-household-items/
This pile of toothpicks does not display any form of organization or structure. The only pattern that may be recognized is that all the objects in the image are toothpicks, but none of them follow straight structural lines.
Visually Speaking 