Orthographic Projection
Orthographic projection is the core of the paper: converting a described or sketched object into aligned front, top and side views in first angle.
First-angle projection is the Indian standard
The object is placed between the observer and the plane. The front view (elevation) is projected on the vertical plane, the top view (plan) on the horizontal plane, and the side view on the profile plane. In first angle the plan is below the elevation, the left-side view is placed on the right, and the right-side view is placed on the left. Views line up: the plan shares width with the elevation; the side view shares height.
Drawing rules
Visible edges: continuous thick. Hidden edges: dashed. Centre lines: chain thin. Choose the front view to show the characteristic shape and the fewest hidden features. Two well-chosen views usually define the object; add a third only when it removes doubt.
Worked example
An L-shaped block stands on its longer leg. The front view shows the L; the top view is a rectangle with a hidden line for the vertical step; the side view is a rectangle showing the step height. Reasoning: the front view captures the profile, the top view gives depth and width, and the side view confirms the step. Align the step across all views before darkening lines.
Traps
Drawing the plan above the elevation (third angle); putting a left-side view on the left; omitting hidden lines that explain a bore; using a centre line as an outline; drawing views at different scales; darkening construction lines.