Drawing Practices (Pictorial Drawing) – Isometric Drawing

Subject: Basic Technology
Class: JSS 3
Term: First Term
Week: 9
Age: 12-15 years
Topic: Drawing Practices (Pictorial Drawing) – Isometric Drawing
Sub-topic: Definition and Construction of Simple Objects
Duration: 60 minutes

Behavioural Objectives

By the end of the lesson, students should be able to:

1. Define isometric drawing.
2. Identify key features of isometric drawing.
3. Draw simple objects in isometric projection.
4. Differentiate between isometric and orthographic projections.

Keywords

• Isometric Drawing
• Pictorial Drawing
• Orthographic Projection
• Isometric Axis
• Isometric Plane
• 30-degree Angle

Set Induction

The teacher displays an isometric sketch of a cube and asks students to describe what they observe. The teacher emphasizes how the object appears three-dimensional on a flat surface.

Entry Behaviour

Students have basic knowledge of two-dimensional drawings from previous lessons.

Learning Resources and Materials

• Isometric graph paper
• Pencils, rulers, and erasers
• 3D models of simple objects (e.g., cubes, pyramids)
• Whiteboard for demonstration

Building Background/Connection to Prior Knowledge

In earlier lessons, students explored orthographic drawings, which show objects from specific views (front, top, and side). Now, they will learn how to represent objects pictorially to show all dimensions at once using isometric drawing.

Embedded Core Skills

• Visual representation
• Analytical thinking
• Fine motor skills (for drawing)

Learning Materials

• Isometric graph sheets
• Models of 3D objects
• Diagrams of isometric and orthographic drawings

Reference Books

• Lagos State Scheme of Work
• Basic Technology Textbook for Junior Secondary Schools
• Engineering Drawing by R.K. Dhawan

Instructional Materials

• Rulers, pencils, erasers, and compasses
• Physical 3D objects like boxes or cubes
• Isometric drawing examples on posters

Content

I. Definition of Isometric Drawing

• Isometric Drawing is a type of pictorial drawing that shows a three-dimensional object on a two-dimensional surface, where the height, width, and depth of the object are represented at equal angles (usually 30 degrees).
• It is called “isometric” because the dimensions along the three axes are measured equally, without distortion.

II. Features of Isometric Drawing

1. All axes (width, height, and depth) are inclined at 30 degrees to the horizontal.
2. Lines parallel to the isometric axis are drawn to scale.
3. Vertical lines remain vertical, while horizontal lines are drawn at 30 degrees to the base.
4. Circles appear as ellipses in isometric projection.

III. Construction of Simple Objects in Isometric Drawing

Steps to Draw a Simple Cube in Isometric Projection

1. Step 1: Draw a light vertical line for the height of the cube.
2. Step 2: From the bottom of the vertical line, draw two lines at 30 degrees to the horizontal on both sides to represent the width and depth.
3. Step 3: Complete the top face by drawing parallel lines to the initial 30-degree lines.
4. Step 4: Join all corners to form a cube.

Example of Simple Objects to Draw

1. Cube
2. Cuboid
3. Cylinder
4. Triangular prism
5. Pyramid

Evaluation (Fill-in-the-Blank Questions)

1. __________ drawing shows a 3D object on a 2D surface.
   (a) Isometric (b) Orthographic (c) Freehand (d) Linear
2. Isometric drawings use lines inclined at __________ degrees to the horizontal.
   (a) 60 (b) 30 (c) 45 (d) 90
3. __________ lines remain vertical in isometric drawings.
   (a) Horizontal (b) Oblique (c) Vertical (d) Inclined
4. A __________ in isometric view looks like an ellipse.
   (a) Triangle (b) Circle (c) Rectangle (d) Square
5. The term “isometric” means __________.
   (a) equal measurement (b) straight view (c) 3D view (d) drawing without angles
6. In isometric drawing, the height is represented along the __________ axis.
   (a) vertical (b) horizontal (c) depth (d) oblique
7. Isometric drawings are useful because they show __________ dimensions at once.
   (a) one (b) two (c) three (d) four
8. An orthographic drawing shows an object from __________ views.
   (a) 1 (b) 2 (c) 3 (d) 4
9. The angle used to draw the isometric axis is __________ degrees.
   (a) 30 (b) 60 (c) 45 (d) 90
10. An isometric projection gives the impression of a __________ object.
    (a) flat (b) curved (c) 2D (d) 3D

Class Activity Discussion (FAQs)

1. What is isometric drawing?
   Isometric drawing shows a 3D object on a flat surface with equal measurements on all axes.
2. What makes isometric drawings different from orthographic drawings?
   Isometric drawings show all dimensions at once, while orthographic drawings show only one view at a time (front, top, or side).
3. Why are isometric drawings important?
   They help visualize 3D objects easily on paper, useful in technical and engineering drawings.
4. What angle is used for isometric axes?
   Each axis is inclined at 30 degrees from the horizontal.
5. Why do circles appear as ellipses in isometric drawings?
   Because the circular shape is distorted when drawn at an angle.
6. What materials are required for isometric drawing?
   Pencils, rulers, isometric paper, and erasers.
7. How do you draw a cube in isometric view?
   Draw vertical and 30-degree lines to form the three visible faces of the cube.
8. Can isometric drawings represent curved objects?
   Yes, but circles appear as ellipses.
9. What is the purpose of using isometric graph paper?
   It makes it easier to draw objects with accurate angles and measurements.
10. How can isometric drawings be applied in real life?
    They are used in architecture, engineering, and product design to represent 3D objects.

Teacher’s Activities

1. Demonstrate how to draw a simple cube using isometric projection.
2. Display various examples of isometric and orthographic drawings.
3. Guide students as they practice drawing simple objects.

Learners’ Activities

1. Practice drawing a cube and other simple objects on isometric graph paper.
2. Compare isometric and orthographic drawings.
3. Participate actively in class discussions.

Evaluation Questions

1. Define isometric drawing.
2. What is the importance of isometric drawing?
3. Describe the steps for drawing a cube in isometric view.
4. List three objects that can be drawn in isometric projection.
5. What is the difference between isometric and orthographic projections?
6. Why are isometric axes inclined at 30 degrees?
7. How does a circle appear in isometric projection?
8. What materials are needed for isometric drawing?
9. Explain the role of isometric paper in technical drawing.
10. What fields make use of isometric drawings?

Conclusion

The teacher reviews students’ drawings and provides corrections where necessary. Feedback is given on their understanding of isometric drawing.