Quick Notes

The flat surface of an object.

• Horizontal plane
• Vertical plane
• Inclined plane

A straight line that is perpendicular or that forms a right angle to any line on the plane.

Images formed on a plane when the projected line from an object is perpendicular to the plane.

The diagram above shows the projection of an object on a vertical plane.

The resulting projection is an orthogonal projection because the line projected from an object to the plane is normal.

1. Identify the type of plane and the direction in which the object should be projected.
2. Draw normal lines from all vertices of the object to the plane. Make sure all the normal lines are straight and upright so that the length of projected sides and the length of sides of the object are the same.
3. Connect the points of intersection of the normal to the plane to draw the shape of orthogonal projection.
4. Redraw the orthogonal projection with actual measurements. Label all vertices and side lengths.

The following diagram shows a cylindrical object on a horizontal plane.

Given that the diameter of the cylinder is \(4 \text{ cm}\) and its height is \(6 \text{ cm}\).

a) Draw the orthogonal projection of the cylindrical object on a horizontal plane as viewed from \(Z\).