Why Multiple Calculations?

To achieve sightlines to a performance or presentation area, there are typically two approaches that are used, depending on the specific viewing requirements.

Single Row Sightline - The intent is for a person to see a viewing point over the head of the person directly in front of them.

Alternating Row Sightline - The intent is for a person to see a viewing point over the head of the person two rows in front of them.

A single row sightline is common in modern cinemas, where "stadium seating" is incorporated, and the viewing point of the bottom of the screen is relatively high.  An audience member is able to easily see over the person sitting in front of them without distraction.  While this allows for a consistent seat plan arrangement, it also requires a substantial elevation change depending on the number of rows and viewing height.

An alternating row sightline is common in most performance venues, where the elevation change needs to be kept reasonably short, whether it be for floor level alignments, wheelchair access, or other building constraints.  A common tool is to alternate the position of the seats every other row such that a patron can look between the people in the seats directly in front, and over the head of the patron two rows in front.

A common way to achieve an alternating row sightline is to vary the quantity of seats in each row such that one seat is on center, and the one behind it is to the side of center.  As a result, we end up with an alternating set of odd and even seats per row.

Because of the general desire to maintain a common alignment at the ends of rows, a typical tool is to vary the widths of seats.  In the United States, this is typically done by adjusting the distance between standards by 1".  It is not uncommon for a venue to use 3-4 seat sizes, ranging from 19" wide to 24" wide seats (widths measured from center of armrests) to achieve the stagger and alignment.  As a result, the seat layout and quantities can vary depending on the length of the row, the available seat sizes, whether seats are odd or even, and how many of each size of seat is desired.  The granularity of the application is achieved by adjusting these calculations, as well as the sort order of the seats in each row.

Important Note

While good design practice, the application will work without adjusting any of these settings.  The default settings use four seat sizes, attempt an even distribution of seat sizes, place the larger seats in the center of a row, and stagger the rows based on how best the first row fits.