PICTORIAL DRAWING

3.1 Introduction

When you look at a picture of any object such as a plane, a ship or a mountain, it shows that you are looking at the real representation of the object even if you have not seen, touched or used it before. A pictorial drawing shows a picture in three dimensions. It may be a dimensional drawing or a sketch. You can use sketches of pictorial drawings to express ideas to solutions when you are designing articles.

In this chapter, you will represent objects in three dimensions (3D).

3.2 Principles used in Pictorial Drawing

Principles of pictorial drawing are guidelines you can use when making a 3D drawing.

Activity 3.1

Exploring principles used in pictorial drawing

What you need: Your school or home environment, exercise book, pen or

pencil

What to do: In pairs, carry out this activity

1. Select some objects from your environment such as matchbox, a metallic box, a box of tea leaves, etc

3.3 Isometric Projections

You can use the same principles used in the previous activity to draw object in isometric projections.

Activity 3.2

Applying principles of pictorial drawing to draw blocks in isometric projections

What you need: Pictures of blocks, (full, cut, curved and circular), 2H pencil, ruler, pair of compasses, dividers, eraser, T-square, board and clips

What to do: In pairs, carry out this activity.

1. Draw blocks in isometric projection, starting with full blocks (Figure 3.3).

3.4 Drawing cut Blocks in Isometric Projection

You can still apply the principles of pictorial

Present your work to the teacher for marking.

Below are the steps of how you come up with the isometric cut block (Figure 3.9).

Steps (Figure 3.10)

▸ Draw the isometric box using overall dimensions.

▸ Fill in the shape of the block using the given dimensions.

▸ The inclined side will be included in the box last.

3.4 Drawing Curved and Circular Blocks in Isometric Projection

You can continue to use the same principle of pictorial drawing. To drow curved or circular surfaces, you need to first learn how to draw isometric circles.

Activity 3.3 Drawing blocks with isometric curves and circles

What you need: 2H pencil, ruler, pair of compasses, dividers, eraser,

T-square, board and clips

What to do: Individually, carry out this activity.

1. Using the ordinate method, draw the following curved blocks in isometric projection as shown in Figure 3.20 to Figure 3.22.

3.5 Making Sketches of Simple Objects

Making sketches of objects is important. Sketching helps you to make accurate three-dimensional drawings of objects. The following are examples of objects that can be sketched.

Activity 3.4 Sketching of three-dimensional objects to demonstrate application of three dimensionality

What you need: A pencil HB or H for sketching, objects in your environment and book or drawing paper. What to do: In pairs, carry out this activity.

1. Using the sketching techniques you have learnt, sketch the objects used in your environment such as a flask, a box, a tin of paint, a pot, a cup, a fridge, etc.

2. Share your work with the class.

3.6 Modelling Three-dimensional Objects

You can model three-dimensional objects using locally available materials.

Activity 3.5

Modelling three-dimensional objects using locally available materials

What you need: Locally available materials such as clay, wires, wood, cardboard, manila paper and sketches of models

What to do: Individually, carry out this activity.

1. Select suitable modelling materials.
2. 2. Choose models you can make easily and are common or used in you environment such as a phone, radio or a bar of soap, etc.

3. Before making the model, make sketches to guide you.

4. Share your work with the class.

3.7 Oblique Projection

Oblique projection is similar to isometric projection. With oblique projection you only change the angles of the three axes and halve the length.

Example:

3.7 Drawing Circles in Oblique Projection

The drawings below demonstrate construction of circles in oblique projection. The method is the same as isometric projection except that measurements for one side, preferably the length will be reduced by 1/2 or 3/4 depending on the type of oblique projection used.