Projections of points: a solved example
Draw the projections of the following points on a common reference line: A, 25 mm above HP and 35 mm in front of VP; B, 20 mm above HP and 40 mm behind VP; C, 30 mm below HP and 25 mm behind VP; D, 35 mm below HP and 30 mm in front of VP; E, in HP and 30 mm in front of VP.
Every line below was drawn and checked by Graspline's own geometry engine, by the textbook method, one step at a time with the reason for each.
The construction, step by step
Draw the reference line XY
XY is the line where HP and VP meet. Front views go above XY for points above HP and below XY for points below HP; top views go below XY for points in front of VP and above XY for points behind VP. A point in a plane has that view on XY itself.
Locate point A
A is 25 mm above HP and 35 mm in front of VP (first quadrant).
Draw a projector (vertical line). Mark the front view a′ 25 mm above XY and the top view a 35 mm below XY.
Locate point B
B is 20 mm above HP and 40 mm behind VP (second quadrant).
Draw a projector (vertical line). Mark the front view b′ 20 mm above XY and the top view b 40 mm above XY.
Locate point C
C is 30 mm below HP and 25 mm behind VP (third quadrant).
Draw a projector (vertical line). Mark the front view c′ 30 mm below XY and the top view c 25 mm above XY.
Locate point D
D is 35 mm below HP and 30 mm in front of VP (fourth quadrant).
Draw a projector (vertical line). Mark the front view d′ 35 mm below XY and the top view d 30 mm below XY.
Locate point E
E is in HP and 30 mm in front of VP (in HP).
Draw a projector (vertical line). Mark the front view e′ on XY and the top view e 30 mm below XY.
Result
All points are drawn on one reference line, 30 mm apart. Rule to remember: the front view records the distance from HP, the top view records the distance from VP.
✓ Verified: each view is on its projector at the stated distance.
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