PERSPECTIVE MEASUREMENTS
Measuring Depth
Measuringperspective depth is m difficult than
ore
gauging heights and widths in linear perspective. Various
methods of perspective construction establish depth in
different ways. Once we establish an initial depth
judgment, however, we can make succeedingdepth
judgments in proportion to thefirst .
Subdividing Depth Measurements
There are two methods for subdividing depth
measurements in linear perspective: the method of
diagonals and the method of triangles.
Method of Diagonals
In any projection system, we can subdivide a rectangle
into four equal parts by drawing two diagonals.
• For example, if we draw two diagonals across a
rectangular plane in perspective, they will intersect at
the geometric center of the plane. Lines drawn through
this midpoint, parallel to the edges of t heplane, will
subdivide the rectangle and its receding sides int o
equal parts. We can repeat this procedure t osubdivide
a rectangleinto any even number of parts.
To subdivide a rectangle into an odd number of equal
parts, or to subdivide its receding edges into a series of
unequal segments, its forward edge must be parallel to
the picture plane(PP) so that it can be used as a
measuringline (ML).
• O t h forward edge of the rectangle, we mark off the
n e
sameproportional subdivisionsto be made in the
depth of the perspective.
• Fromeach of the m
arked points, we draw parallel lines
that converge at t hesame point as t herecedingedges
of the plane.
• Then we draw a single diagonal.
• At each point where this diagonal crosses the series of
receding lines, we draw lines parallel to the forward
e These mark off the desired spaces, w
dge.
hich
diminish asthey recede in perspective.
• If the rectangle is a square, then t hesubdivisions are
equal; otherwise, the segmen G2&R&