Question

A non-isometric line is drawn by

• A. using angle of inclination.
• B. using co-ordinate method.
• C. using a line parallel to $45^{\circ}$ to horizontal.
• D. using a line perpendicular to horizontal.

Hint:

Never measure lengths directly along a non-isometric line! Always construct an isometric “box” around the shape, find the coordinates of the endpoints along the edges of the box, and connect them.

Answer 1

The Correct Option is B

Step 1: Definition of Isometric and Non-Isometric Lines:
In isometric projection, any line that is parallel to one of the three principal isometric axes (which are inclined at $30^{\circ}$, $90^{\circ}$, or $150^{\circ}$ to the horizontal reference line) is called an isometric line. These lines are foreshortened uniformly and can be measured directly using an isometric scale. Any line that is not parallel to any of these three axes is called a non-isometric line.

Step 2: Drawing Non-Isometric Lines:
Because non-isometric lines are not parallel to the isometric axes, they do not undergo the same uniform foreshortening. Consequently, their lengths cannot be measured directly along isometric lines.

Step 3: Evaluating the Co-ordinate (Box) Method:
To draw a non-isometric line, we must locate its endpoints first. This is achieved by measuring the perpendicular co-ordinates (or distances) of these endpoints along isometric directions (using the box method or coordinate method) and then joining the two points with a straight line. Therefore, option (B) is the correct choice.