Orthographic projection

Orthographic Projection: The Superpower of Seeing All Sides at Once!

Haya basi, student! Welcome to one of the most important topics in Technical Drawing. Ever looked at a building plan or a picture of a machine part and wondered how a flat piece of paper can show every single detail of a 3D object? It’s not magic, it’s a powerful technique called Orthographic Projection. Think of it as a special kind of superpower that lets you see an object from the front, the top, and the side, all at the same time on one sheet of paper! By the end of this lesson, you'll be able to unlock this superpower too. Twende kazi!

What Exactly is Orthographic Projection?

Let's break down the name. "Ortho" comes from a Greek word meaning 'right' or 'straight'. "Graphic" means drawing or picture. So, Orthographic Projection is simply a way of drawing an object from different right-angle views. The goal is to represent a three-dimensional (3D) object in two dimensions (2D) without any distortion of its shape or size.

The easiest way to understand this is with the "Glass Box" method. Imagine you have an object, let's say a charcoal jiko. Now, picture placing this jiko inside a transparent glass box.

Image Suggestion: A realistic 3D render of a simple, classic Kenyan charcoal jiko. The jiko is suspended inside a transparent, glowing glass cube. Dotted lines are projected from the corners and edges of the jiko straight outwards to the inner surfaces of the glass box, illustrating the concept of projection. The style should be clean and educational.

      +---------------------+
     /|                    /|
    / |       TOP         / |
   +---------------------+  |
   |  |                  |  |
   |  |   (Jiko inside)  |  |  SIDE
   |  +------------------+  |
   | /       FRONT      | /
   |/                    |/
   +---------------------+

If you look at the box straight from the front, you see the front view. If you look straight down from the top, you see the top view. And from the side, you see the side view. Now, imagine you carefully unfold this glass box. What you get is the orthographic projection!

The Principal Views: Your Drawing's Best Friends

In orthographic drawing, we usually focus on three main views. These are called the Principal Views.

• Front View (or Front Elevation): This is the main view. You should choose the side of the object that shows the most detail or its most characteristic shape. For example, the front of a matatu would be the side with the grille and headlights.
• Top View (or Plan): This is what you see looking directly down on the object. It shows the length and width. Think of how a bird would see a building from the sky.
• Side View (or End Elevation): This shows what the object looks like from the side (usually the left or right). It shows the depth and height.

First Angle vs. Third Angle: The Two Systems

Now, this is very important! How we arrange these views on paper depends on the system we use. There are two main systems in the world: First Angle and Third Angle Projection.

In Kenya, we follow the British Standard, so we almost always use First Angle Projection. It's crucial to know the difference.

1. First Angle Projection (This is our system!)

In First Angle, the object is placed between the observer and the projection plane (the glass). You 'project' the view through the object onto the plane behind it.

• The Top View (Plan) is drawn BELOW the Front View.
• The Right-Side View is drawn on the LEFT of the Front View.
• The Left-Side View is drawn on the RIGHT of the Front View.

Here is the international symbol for First Angle Projection. You will see this on many technical drawings.

    Symbol for First Angle Projection:

      -----         -------
     /     \       |       |
    |-------| -----|-------|
     \     /       |       |
      -----         -------

2. Third Angle Projection

In Third Angle, the projection plane is between the observer and the object. It's like you are looking through the transparent glass at the object.

• The Top View (Plan) is drawn ABOVE the Front View.
• The Right-Side View is drawn on the RIGHT of the Front View.

While you need to know it exists (it's used mainly in the USA), always remember to use First Angle for your work here in Kenya unless you are told otherwise. Sawa?

Let's Draw! Step-by-Step in First Angle

Let's draw a simple object: a wooden block with a step cut out of it. We will draw the Front, Top, and Right-Side views.

Image Suggestion: A simple, textured wooden block sitting on a white surface. A large step is cut out of its top-right corner. Arrows labelled "Front View," "Top View," and "Right-Side View" point at the corresponding faces of the block. The lighting is bright and clear, highlighting the object's geometry.

Here is how we arrange the final drawing:

      (Vertical Plane)
            ^
            |
            |
            |   FRONT VIEW
            |
   -----------------------------> (Horizontal Plane - XY Line)
            |
            |
            |   TOP VIEW (PLAN)
            |
            v

And here is the full layout with the side view included:

  +--------------------------------+--------------------------+
  |                                |                          |
  |      SIDE VIEW                 |      FRONT VIEW          |
  |      (End Elevation)           |      (Elevation)         |
  |                                |                          |
  |                                |                          |
  +--------------------------------+--------------------------+
  |       (45-degree line here)    |      TOP VIEW            |
  |        to project points       |      (Plan)              |
  |                                |                          |
  +--------------------------------+--------------------------+

The Process:

1. Establish your XY Line: Draw a horizontal line across your paper. This separates the plane for the Front View from the plane for the Top View.
2. Draw the Front View: Look at the object from the front and draw what you see above the XY line.
3. Project Down for the Top View: From every corner of your Front View, draw very light, thin vertical lines (projection lines) downwards. Now, draw the Top View below the XY line, using these projection lines to get the width perfectly correct.
4. Project for the Side View: Draw a vertical line to separate the Front and Side views. Now, draw a 45° line from the corner where your main horizontal and vertical lines meet. Project horizontal lines from your Top View to this 45° line, and then project them vertically upwards.
5. Complete the Side View: Project horizontal lines across from your Front View. Where these lines intersect with the ones you brought up from the Top View, you will have the exact shape of your Side View!
6. Finish Up: Go over the final outlines of your three views with a darker, thicker line. Leave the projection lines light and thin. Add dimensions, and you are done! Vizuri sana!

A Real-World Kenyan Example

Think about a fundi (artisan) in a workshop in Gikomba or Kamukunji who needs to make a window frame. The customer gives him a technical drawing.

• The Front View shows the overall height and width of the frame, and the pattern of the window panes.
• The Top View shows how thick the frame is from front to back.
• The Side View shows the profile of the frame, including any special grooves for the glass.

Without this orthographic drawing, the fundi would just be guessing. With it, he can make a perfect window frame that fits exactly, with no wasted wood or metal. This is why technical drawing is the language of making things!

Summary: Key Takeaways

Let's wrap it up! Here are the most important points to remember:

• Orthographic Projection is a method to draw a 3D object in 2D using a series of "flat" views.
• The three main views are the Front View, Top View (Plan), and Side View.
• The "Glass Box" is a great way to visualize how the views are projected.
• In Kenya, we use the First Angle Projection system. This means the Top View goes below the Front View.
• Always use light construction/projection lines and dark, clear object lines. Precision is key!

Now it's your turn. Grab a simple object around you – a book, a sufuria, your phone – and try to sketch its three principal views in First Angle. Practice is the only way to become an expert. Good luck!