3.6 Doric Order
In this figure we see an image of the Segesta Greek temple. This temple, which was never finished, was built during the 5th century BC, and represents a fine example of the Doric order, the oldest of the three orders of Greek architecture (Doric, Ionic, and Corinthian). In the Doric order, a column is composed of a shaft, an echinus and an abacus. The abacus is shaped like a squared slab that stands on top of the echinus. The echinus is similar to an inverted cone frustum that stands on top of the shaft. The shaft is similar to a cone frustum with twenty flutes around it. These flutes have a semi-circular shape and are carved along the shaft. The Doric columns also present an intentional deformation called entasis. The entasis is a small curvature given to the columns, which is believed to have been used to correct an optical illusion that makes straight columns seem curved. When the Romans adopted the Doric order, they introduced some modifications, in particular, to the flutes, which, in many cases, were simply removed.
The Doric order, exemplified in the Greek Temple of Segesta, which was never finished. Photograph by Enzo De Martino.
For simplification purposes, we are going to start by sketching a Doric column (without flutes) in two dimensions. In the following sections, we will extend this process to create a three-dimensional model.
The same way a Doric column can be decomposed into its basic components - shaft, echinus and abacus - its corresponding drawing can too be decomposed in components. Therefore, we will create separate functions to draw the shaft, the echinus, and the abacus. This figure shows a reference model.
The Doric column for reference.
Let us start by defining a function for the shaft:
shaft() = line(xy(-0.8, 10), xy(-1, 0), xy(1, 0), xy(0.8, 10), xy(-0.8, 10))
In this example, we used the line function that, given a sequence of positions, creates a line with vertices on those positions. Another possibility, probably more appropriate, would be to create a closed polygonal line, something we can do with the polygon function, avoiding the repeated position, i.e.:
shaft() = polygon(xy(-0.8, 10), xy(-1, 0), xy(1, 0), xy(0.8, 10))
To complete the figure, we also need a function for the echinus and another for the abacus. The reasoning for the echinus is similar:
echinus() = polygon(xy(-0.8, 10), xy(-1, 10.5), xy(1, 10.5), xy(0.8, 10))
For the abacus, we could follow a similar strategy or, alternatively, we could employ the function that creates rectangles. This function requires two positions to define a rectangle:
abacus() = rectangle(xy(-1, 10.5), xy(1, 11))
Finally, we have the function that creates a Doric column, which sequentially calls the shaft, echinus and abacus functions:
doric_column() = begin
shaft()
echinus()
abacus()
end
This figure shows the result of invoking the doric_column function.
A Doric column.
