Example of Alteration of Reference Line Method:

A right regular hexagonal pyramid 80 millimeter in height and side of base 35 millimeter, having an edge of the base in HP and the face having that edge is inclined at 47^o to HP. Sketch its projection.

Solution

(a)   Sketch the hexagonal plan 1, 2, 3, 4, 5, 6 along with side 35 millimeter and one side of base 1, 6 is perpendicular to VP.

(b)   Complete elevation along with base in HP and axis of such pyramid perpendicular to HP and parallel to VP.

(c)    To receive the final plan via alternation of reference line method Sketch another reference line X₁ Y₁ passing via point 1′ and 6′ at an angle of 47^o  along with 1′ O′ or like slant edge of pyramid.

Note:  X₁Y₁ is intersection of VP and auxiliary HP on that plan is to be drawn.

(d) Sketch projections from various points in elevation that are perpendicular lines to X₁ Y₁.

(e) Get the distance of points 1, 2, 3, 4, 5, 6 and O from XY and mark 1₁, 2₁, 3₁, 4₁, 5₁, 6₁ and O₁ on respective projectors that are perpendicular to X₁ Y₁ as an example to situate point 1₁, distance 1′ 11 is equal to 1′ 1.

(f) Sketch hexagonal base via joining 1₁ 2₁ 3₁ 4₁ 5₁ 6₁ is like visible and connect O₁1₁, O₁2₁, O₁6₁, O₁5₁ by dark line is like visible and O₁3₁ and O₁4₁ via dotted line is like not visible and complete the plan.