# One Point Perspective Drawing

Subject : Basic Technology

Class : Basic 9 / JSS 3

Term : 1st Term / First Term

Week: 10

Topic:

One Point Perspective Drawing

Previous Knowledge : The pupils have been taught

Isometric Drawing

during their previous lesson or class

Behavioural Objectives : By the end of the lesson, learners will be able to

• define oblique drawing
• say the steps that are involved in oblique drawing

Content

1. Definition
2. Principles
3. Practise

Definition

One point perspective can be defined as:

“…a mathematical system for representing three-dimensional objects and space on a two-dimensional surface by means of intersecting lines that are drawn vertically and horizontally and that radiate from one point on a horizon line…”

Although this definition sounds complicated, the concept is relatively simple. One point perspective is a drawing method that shows how things appear to get smaller as they get further away, converging towards a single ‘vanishing point’ on the horizon line. It is a way of drawing objects upon a flat piece of paper (or other drawing surface) so that they look three-dimensional and realistic.

Drawing in one point perspective is usually appropriate when the subject is viewed ‘front-on’ (such as when looking directly at the face of a cube or the wall of building) or when looking directly down something long, like a road or railway track. It is popular drawing method with architects and illustrators, especially when drawing room interiors.

Principles

In one point perspective, surfaces that face the viewer appear as their true shape, without any distortion. They are drawn using primarily horizontal and vertical lines, as illustrated by the diagram below:

In this one point perspective photo, surfaces facing the viewer are distorted and show their true shape. For example, we see the side of the bath, window and facing surfaces as ordinary squares and rectangles. Their sides are parallel with the edges of the photograph.

Surfaces that travel away from the viewer, on the other hand, converge towards a single ‘vanishing point‘. This is a point that is located directly in front of the viewer’s eyes, on a ‘horizon line’ (also known as an ‘eye level line’), as illustrated in the photo below:

All receding edges of the buildings in this one point perspective photo angle towards the single vanishing point. The position of the vanishing point tells us that the photographer was crouching down, with his eye level lowered.

It is possible to draw over photographs to identify vanishing points, horizon lines and true shapes. Studying the work of famous artists can also help you gain an understanding of one point perspective, as shown in the example by Vincent van Gog below.

‘Bedroom in ares’ by Vincent van Gogh – identifying perspective lines

Key Points:

• Surfaces that face the viewer are drawn using their true shape
• Surfaces that travel away from the viewer converge towards a single vanishing point

Principal planes of projection

1. Vertical Plane: The views on the vertical plane are front elevation and end elevation (side elevation).
2. Horizontal plane: This shows the plan in the quadrants in the figure above. The quadrant 0-90o contains the first angle and quadrant 180o-270o contains the third angle. Since the second and fourth quadrants would combine the two systems, we do not use them.

Assesments

Briefly explain the the principal planes of projection

Week 2)

Processing of Materials (Wood) – contd.

Outline:

— Concepts of Wood processing – growth, felling

Wood processing is an engineering discipline comprising the production of forest products, such as pulp and paper, construction materials, and tall oil. Wood is obtained from trees that grow all around us. However, wood cannot be used to produce the materials needed domestically and industrially, if the wood does not pass through the necessary stages of being processed. Wood processing also produces additives for further processing of timber, wood chips, cellulose and other prefabricated material.

Wood/Timber growth:

Timber is a piece of wood used for various domestic and industrial woodwork. Timber is obtained from trees especially the trunk and branches. Trees that provide timber are usually trees with big trunk, these types of trees are grown in the Southern part of Nigeria in Rain Forest vegetation. These trees grow fast in the southern region of Nigeria because of the heavy rains and the long period of rain in that region annually. Common examples of such trees are mahogany, obeche, teak, oak, etc. The entire process of processing of timber can be summarized in the chart below:

Wood Conversion → Felling of trees → Wood seasoning → Wood preservation

Felling of Trees:

Felling is the process of downing individual trees, an element of the task of logging. The person cutting the trees is a feller. Felling of trees is done with the aid of chain saws as shown in the image below. The tree is then cut and arranged neatly.

Felling of a tree

Felling can be fell either by hand felling or by feller buncher. Hand felling processes is the using of an axe or saw, used to fell a tree. Feller buncher is a motorized vehicle with an attachment which rapidly cuts and gather several trees in the process of felling them.

Assessment

• Briefly explain the following terms; Wood processing, Timber, felling of trees.

## Week 4)

### Outline:

— Manufactured board – defects, preservations

Introduction:

Various abnormal conditions and features of wood which permanently reduce the economic value of wood are termed as defects. However, defect caused by fungal attack and decay in wood is known as Unsoundness. The term is generally applied to the discontinuity of tissues and abnormal fibre development in wood, and unsoundness to some form or stage of decay in wood. These defects and or unsoundness in wood may either just reduce its utility or render it entirely valueless.

Wood preservation is the process of adding chemical to wood so as to prevent termites, insects, weevils and fungi from attacking the wood. These chemicals are called preservatives, it can be applied to wood through spraying or brushing. Example of wood preservatives are creosote, coal-tar, solignum, chlorinatephenol, paints etc.

Defects in Wood

Defects are faults or irregularities in wood caused either naturally or during processing of the wood which reduces the value or quality of the timber.

• Natural defects: these are defects which occur during the growth of a tree, they include the following:
1. Heart shake: these are visible splits on the cross-section of the centre of the log extending along the rays
2. Star shake: this is similar to heart shake, but with more shakes are observed in the star formation
3. Cup shake: these are visible cracks that go part ways around the growth ring
4. Knot: this is a defect that occurs at the branch of a tree, it is enclosed within a growing tree and if it falls to the ground from the tree, it may leave a knot hole on the tree.
5. Cross-grain: this is the condition which occurs when the wood fibre is not aligned parallel to the axis of the piece of wood, it is caused by the manner the tree grew and it gives pant ow strength.

• Artificial Defects: this is also referred to as processing defects, they are caused by careless handling and faulty seasoning and preservation of wood. There are different types –
1. Cup: this is a concave curvature across the face of the timber. It is caused by bad stacking during drying. Plain sawn planks are more are more affected than quarter sawn.
2. Bow: this is either concave or convex curvature along the length of a plank
3. Twist: this is a spiral form of distortion along the length of a plank
4. Check: this is the separation of wood along the grain of a board
5. Insect attacks: These are visible minute holes seen on the surface of boards. The sapwood is more readily attacked than the heartwood. Dry planks are more readily attacked.

Assessment

• List five Natural and Artificial defects of wood

Presentation :

The Topic is presented step by step for easy assimilation by the learners.

Step 1 : The teacher revises the previous topics that had been taught during the precious lessons

Step 2 : The subject teacher introduces the new topic of the learners

Step 3 : He or she allows the students to give their own contributions and he corrects them when the needs arise

Evaluation

Briefly define the following terms :

• What do you understand by Oblique drawing
• Briefly explain the principal views of orthographic projection