Quadrilateral Perspective

(continued 5)

Figure nº 29:

For better understanding of the raising of the spiral staircase steps, examine the process used to raise steps 1 and 3. Considering that step 1 is frontal, it was raised on the box front wall. Step 3 was constructed on the lateral wall.

See in Figure nº 27 the raising of all staircase steps.


Figure nº 30 shows the construction of a door ajar.


See how it was constructed:


1 —

Calculate the door width on the width measurement line; transfer this width to the place of its construction by the vanishing point.


2 —

The same measurement is found at the side of the door opening.


3 —

Prolong line a, b, that goes from the door post up to the vanishing point and find point c. The distance between points c and e has the same dimension of the door opening.


4 —

Construct the angle of the door opening.


5 —

Select any point of this angle. See point d. From there to point e, sketch a straight line. Prolong this straight line up to the horizon and locate the vanishing point f.


6 —

Sketch a line from point g to point f. Prolong this line until crossing with the vertical line referring to the door height.


7 —

Calculate the door thickness and sketch a line parallel to the door vertical line.



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