Applied Interior Design

Introduction
In the following pages, you will review:

o What is meant by conical perspective?

o What is the difference between one-point and two-
point perspective and what are their applications in
interior design?
o What is the perspective centre?

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What is conical perspective?
Conical perspective is a system of representation in which three-dimensional
bodies appear in the field of view of a single observer. Conical perspective
includes linear perspectives with one, two or three vanishing points. Conical
perspective is so called because it refers to the “cone of vision” of a typical
observer.

To better understand what we mean by conical perspective, we must first

understand how our eyes work. Our eyes are only able to receive light bouncing
off objects within a certain area of sight. Light rays pass through the pupil of the
eye to reach the retina, creating an image that is interpreted by our central
nervous system.

Imagine your area of sight as a 60-degree angled cone of undistorted vision, with
the apex of the cone at your eye. This represents the cone of vision we learned
about in Module 2. Now, imagine adding a vertical plane slicing through this
imaginary cone of vision from top to bottom, with the flat part of the plane facing
the apex of the cone. The image on this picture plane is in conical perspective.
Refer to the image below for better understanding.

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So, conical perspective is a system of graphic representation in which a three-

dimensional object is drawn on a two-dimensional plane as it would appear to the
human eye from a specific point of view. Conical perspective involves projecting
the real-world parallel lines of an object onto a plane with a set of converging
lines that meet at a specific point. This causes the distortion of dimensions.

As we’ve learned, in a perspective drawing, objects seem smaller the further they
are from the observer. Conical perspective differs from the forms of parallel
projection (such as axonometric projection) in that parallel projection drawings
have no vanishing points, whereas perspective drawings do.

Early paintings and drawings did not use conical perspective. Instead, elements
were larger or smaller according to their thematic or spiritual importance, rather
than their physical distance from each other or from the viewer. While some
attempts to develop theories of perspective emerged around the 5th century BCE
in ancient Greece, various cultures, for example China and Japan, used oblique
projection instead.

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In 1415, Filippo Brunelleschi introduced the earliest form of linear perspective to
the artistic Renaissance underway in Italy. Brunelleschi calculated the scale of
objects to appear within a painting in order to make them look realistic. He
demonstrated the accuracy of his techniques by sketching the Baptistery in
perfect perspective. Brunelleschi’s methods were later employed by artists such
as da Panicale and Masaccio.

Masolino da Panicale’s St. Peter Healing a Cripple and the Raising of

Tabitha (1423) seen here is the earliest known artwork to use a consistent
vanishing point.

In 1435, Leon Battista Alberti wrote De pictura, a treatise on proper methods of

showing distance in painting. In 1470, Piero della Francesca formulated his
theory based on planar projections in De Prospectiva pingendi, explaining how
the rays of light, passing from the viewer’s eye to the landscape, would strike the
picture plane.

In 1509, Luca Pacioli’s Divina proportione summarized the use of perspective in

painting, inspired by della Francesca’s theories.

These advancements in our understanding of how to depict perspective and the

artistic representation of space and depth have made possible our modern
conception of how to accurately depict conical perspective.

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Applied Interior Design
One-point perspective
When using one-point perspective, there are two types of horizontal lines:
orthogonal and transversal.

We’ve already encountered orthogonal lines—another term for vanishing lines. In

a perspective drawing, these lines are not parallel, but form an oblique angle to
the horizon line.

Lines parallel to the horizon line are called transversal. Of course, this means that
transversal lines are also parallel to each other. These lines do not converge at a
certain point, but they are affected by foreshortening. Transversal lines that are
further away from the picture plane will be smaller and closer together due to
foreshortening. For example, in this photo of a railroad track, notice how the
horizontal railroad ties become smaller and appear closer together as they
recede into the distance.

Two-point perspective
When using two-point perspective, the vanishing lines in a scene converge at one
of two points on the horizon line. If the viewer is facing the edge or corner of a
volume in the scene, the volume must be drawn at an oblique angle. The lines of
the volume therefore move apart toward two different points on the horizon line.

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Applied Interior Design

If you look at a bookshelf head on, the shelves will all appear parallel. To draw
them from this point of view, you only need to use one vanishing point. From this
perspective, the viewer will be able to see the top of the shelves below the
horizon line, and the bottom of the shelves above the horizon line. This creates
an impression of three-dimensionality.

If you turn or shift your position to see the shelves from the side, you’ll notice that
the long sides of each shelf converge toward one point, and the short sides
toward another. You’ll need two vanishing points to draw this perspective.

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It’s possible to combine one-point and two-point perspective. For example, even
if a room has only one vanishing point, if it contains items of furniture arranged at
different angles, they may have additional vanishing lines.

Make sure you’ve mastered the concepts of one-point and two-point perspective
before attempting to use three-point perspective, curvilinear perspective or any of
the other more complicated types of linear perspective.

Use of one-point and two-point perspective in interior

design
So, how are these different kinds of perspective used in interior design drawings?

One-point perspective for capturing frontal views

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Applied Interior Design
One-point perspective is commonly used for interiors with a clear frontal view, such as
looking directly down a hallway. It simplifies the representation of the interior space.

One-point perspective for capturing the space

One-point perspective is also commonly used to illustrate public spaces like restaurants,
cafes, hotel lobbies and spacious residential areas. It is useful for showing the maximum
amount of a given space—though to fully capture the space and all the relevant angles, you
may need more than one image. For example, to represent a rectangular-shaped
restaurant, you can use two one-point perspective views: one from the entrance and one
from the rear of the restaurant.

One-point perspective for emphasis or balance

One-point perspective gives the artist the flexibility to position the vanishing point along the
horizon line, which can allow for dynamic and asymmetrical compositions. Designers can
use it to emphasize specific walls while maintaining balance. On the other hand, when the
single vanishing point is centred in the image, this creates a more balanced composition.

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Applied Interior Design
There are nine principles for using one-point perspective in interior design
drawings:

o All the lines in your drawing are either horizontal or vertical, or

receding to the vanishing point.
o All horizontal lines are parallel to each other.
o All vertical lines are parallel to each other.
o The horizon line is at eye level, which is usually 57 to 63 inches high
when measured from the ground line.
o All horizontal lines are parallel to the horizon line, and all vertical lines
are perpendicular to the horizon line.
o All diagonal lines recede to the vanishing point; these are the
vanishing lines.
o The closer the objects are to the viewer, the more detail they can
see.
o All objects get smaller the further they are from the viewer.
o All objects along the vanishing lines become foreshortened.

Two-point perspective for illustrating dynamic views

Two-point perspective is useful for illustrating interiors with more dynamic views. It adds
complexity by accommodating scenes with varying orientations. This perspective is ideal
when you want to show a space with a dominant object—for instance, showcasing a bed in
a bedroom, a desk in an office or a crib in a nursery.

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Applied Interior Design
Two-point perspective for depicting detailed views

Two-point perspective is particularly advantageous for depicting detailed views of specific

corners of an interior, making it ideal for smaller spaces. Also, the oblique view makes it
possible to show furnishings and other distinct objects and is a valuable tool for specifying
details like upholstery choices.

Here are six principles to keep in mind when using two-point perspective in
interior design sketches:

o All the diagonals in your drawing recede to either one of the

vanishing points.
o All vertical lines are perpendicular to the horizon line.
o There are no horizontal lines except for the horizon line and the lines
of the objects that are precisely at its height.
o The closer the pieces of furniture or decor are to the viewer, the more
detail they can see.
o All objects decrease in size as they recede into the distance.
o All furniture and other interior design elements along the vanishing
lines become foreshortened.

What is perspective centre?

• In geometry, the centre of an element is the point where the mass or weight
of a shape is concentrated. Informally, the centre of an element can be
understood as the point at which a cutout of the shape (with uniformly
distributed mass) could be perfectly balanced on the tip of a pin.

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• In two-dimensional drawing, for simple and symmetrical shapes, like a
circle or a rectangle, the centre is located at the geometric centre.

• For example, the centre of a circle is the point equidistant from the points
along the edge, or circumference.

The centre of a square, rectangle or parallelogram is where the diagonals

intersect

The centre of a triangle is the intersection of the three medians of the triangle
(each median connecting a vertex with the midpoint of the opposite side).

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Applied Interior Design
When two-dimensional shapes are drawn in a three-dimensional perspective,
they retain their individual perspective centres. However, in a perspective image,
shapes undergo foreshortening and the dimensions that recede are distorted.
This means we can’t use a ruler to determine the perspective centre of a three-
dimensional drawing of an object—we have to use other method.

For example, check out this illustration of a square. When we rotate the square
as though it were the face of a cube in a three-dimensional perspective drawing,
the face of the square is distorted by foreshortening. In the drawing where we see
the face of the square head on, the centre of the square is aligned with a vertical
line that intersects the upper and lower edges of the square at their midpoint.
When we rotate the square into the three-dimensional space, the vertical line no
longer cuts the upper and lower edges into two equal segments because of the
distortion caused by foreshortening.

Throughout the rest of this module, we will explore methods for accurately
representing the proportions of three-dimensional objects in a two-dimensional
space and gain a deeper understanding of the perspective centre.

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