In this blog post, we’ll explore why a hanok appears straight when viewed from a distance but shows curved pillars and roofs when approached up close, examining this phenomenon through optical illusions and traditional architectural techniques.
When we see a woman with a slender waist, we perceive the beauty of curves. This stems from the elegance and softness curves provide, and this aesthetic sense is found in diverse places—from natural forms and the human body to artificial structures. However, a body shape that is concave in the center overall can appear unstable for supporting the body. This sense of potential instability can cause psychological discomfort, ultimately affecting the perceived beauty of the form. Conversely, a straight tree offers both the aesthetic appeal of honest form and structural stability. This logic plays a significant role in architecture as well. A sturdy, straight form conveys stability, fostering trust alongside visual beauty.
This principle was applied to the architecture of hanok, the traditional Korean house style. Hanok embodies the Korean philosophy of life, which values harmony with nature. Designed to exist as part of nature rather than merely as a dwelling space, its upright pillars and flat roofs provide structural stability while embodying the visual beauty of straight lines and right angles. Consequently, most Korean hanok feature formal architectural elements like rectangular facades and pillars spaced at regular intervals. This is not merely a consideration of external stability but also a result of pursuing natural beauty.
However, upon approaching a hanok, something peculiar becomes apparent. While appearing rectangular from a distance, with uniformly thick upright pillars and a perfectly horizontal roof, a closer look reveals the house is unexpectedly bent or tilted! Why isn’t the Korean hanok built as straight as one might think, and why does its shape appear distorted from a distance? The answer lies in optical illusions. An optical illusion refers to perceiving the shape of a picture or object differently from reality. Surprisingly, Korean hanok deliberately exploits this phenomenon, intentionally twisting the structure or using curved elements to make it appear perfectly upright. This is called optical correction.
There are several ways we perceive hanok as distorted. That is, there are various optical correction techniques that make the house feel as if it stands straight. The first and most common is the “barrel-shaped pillar.” This is an optical correction technique applied to Korean hanok, and the pillar is more familiar to us from the book ‘The Barrel-Shaped Pillars of Muryangsujeon’. A curved column features its lower third as the most convex part, meaning the column’s thickness is not uniform and the entire structure bulges toward the center. This is because a column of uniform thickness viewed from a distance creates an optical illusion where the center appears concave. By intentionally making the center convex, the column appears to have uniform thickness and is also structurally more stable.
Beyond simply correcting this optical illusion, the curved column also serves to draw visual focus. When viewing a hanok, the gaze naturally converges on the center of the column. Here, the column’s curve stabilizes the line of sight, creating a sense of overall architectural balance. This makes the hanok appear not merely as a ‘standing house’, but as a ‘house achieving harmony’.
Perspective is also a key cause of the optical illusion where the edges of the house appear farther away than they actually are when viewed from the front. For example, while a hanok appears as a precise rectangle when viewed from above, from the front it may show a convex curve at the center or make the edge pillars appear widely spaced despite their uniform intervals. The technique used to compensate for this is called purim. It involves indenting the center of each corner when viewed from above, so that when a person stands in front of the house, the edges appear closer than they actually are. This creates an optical illusion: although the center is actually a concave curve, the house appears flat when viewed from the front.
Additionally, when viewing a row of pillars, the pillars at the edges appear to be open at the top, which is also an optical illusion. In hanok, structural necessity dictates that the pillars supporting the house must be erected vertically. This vertical alignment maximizes compressive force and efficiently supports the structure. However, just as crucial as the pillars standing straight is their shape. To achieve this, the edges of the pillars are slightly inclined inward, making them appear perfectly vertical. This is called ‘ogum’.
When viewed from the front, a hanok displays a geometric beauty where the roof eaves form a horizontal line at right angles to the vertical pillars. Yet, an optical illusion is at play here. If the eaves were truly horizontal, the ends would appear lower from the front, making the edge pillars seem relatively shorter and creating an uncomfortable visual impression. The solution lies in using ‘joro’ (raising the eaves at both ends) and ‘eoseong’ (making the edge pillars taller than the central pillars). This creates a visual horizontal line matching the vertical pillars on the roof and also broadens the view from inside the house outward.
Thus, Korean hanok transcends mere external beauty; every element composing the house is meticulously considered to achieve harmony. This harmony carries significant philosophical meaning, symbolizing balance not only in the house’s residential function but also between nature and humans, and between the architecture and its inhabitants.
This is a method that utilizes an optical illusion to make the hanok appear perfectly upright when viewed from the front. Of course, the degree to which one perceives this illusion varies from person to person, so the shape of a hanok seen head-on may differ slightly for each individual. However, there is an optical illusion that most people fail to notice when viewing a hanok photograph or seeing it in person from the front: the curved pillar. The author of ‘Leaning Against the Curved Pillars of Muryangsujeon’ easily observed the actual shape of the pillars, revealing that curved pillars do not appear to have uniform thickness. This is an unavoidable limitation of hanok architecture, as the illusion requires empty space between the pillars to be fully realized. However, since hanok are primarily residential buildings, walls are required between the columns. Consequently, the full illusion of entasis cannot be experienced. For example, Greek or Roman temples feature empty spaces between their columns; observing such structures can help appreciate the entasis illusion.
Considering structural stability or efficiency in the building process, constructing vertically and horizontally regardless of appearance is rational. Why did Korean ancestors strive to correct this optical illusion when building hanok? It was because they perceived the house not merely as a living space but as a work of art. Therefore, beyond satisfying the structural and functional elements of hanok, they sought to realize visual beauty. They wanted to appreciate the overall appearance of the completed house and to realize the beauty inherent in its form without compromising its essential conditions. The emotion we feel when viewing hanok likely stems from the devotion our ancestors poured into building them.
This meticulous consideration is why hanok, as an artistic expression pursuing harmony between nature and humanity and the balance of beauty and function, continues to move many people today, far beyond being a mere structure.
