What should be the orientation of a horizontal reference line in isometric drawings?

In isometric drawings, the orientation of a horizontal reference line should be horizontal to maintain clarity and proper representation of three-dimensional objects on a two-dimensional plane. This horizontal line serves as a baseline from which other elements are measured and drawn, allowing for accurate proportions and angles in the isometric view.

By keeping the reference line horizontal, it aligns with how the isometric projection represents the three axes of space: the horizontal axis (X), the vertical axis (Y), and the depth axis (Z). The three axes in isometric drawings are typically at an angle of 30 degrees from the horizontal, which creates the illusion of depth and dimension. Therefore, a horizontal reference line is essential for achieving the correct aspect and perspective in isometric visuals.

Having this reference line set horizontally establishes a clear and consistent point of alignment that aids in the accurate depiction of height, length, and depth, enabling viewers and designers to better understand and visualize the object being represented.