DIAGONAL POINT METHOD
Diagonal Points
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• If we draw a45° linefrom the st ationpoint (SP) in a
plan view of t he perspectivesetup, it will in ersect t he
t
picture plane(PP) at t hevanishingpoint for that
diagonal and all lines parallel to it. We call this
vanishing point adiagonal point (DP).
• There is oneDP for horizontal diagonal lines recedingt o
the left (D and another for horizontal diagonal lines
PL),
recedingto theright (D
PR).
• Both diagonal points lie ont hehorizonline (HL),
equidistant from the center of vision (C). F the
rom
geom of the 45° right triangle, we know that the
etry
distance fromeachDP to Cis equal to the distance
from SP to Cin the plan set up.
• Notethat if we m eachDP t owa rd C this is
ove
.
equivalent to theobserver m
ovingcloser t o P If we
P
shift each DP farther away from C theobserver also
,
moves farther away from P
P
---.... AlongHL we est ablish DPL. R
,
emember t hat the
dist ance fromDPLt oCis equal to thedistance of SP
to Cin the plan setup. N that bothD Land DPR
ote
P
would serve the same purpose.
F D we draw aline throughthe left endpoint of
rom PL.
the measurements along GL.
W t his diagonal crosses the lines ont hefloor or
here
ground planet hat converge at C. w drawhorizonta l
e
lines. The result is aperspect ive grid of one-foot
squares on the floor or groundplane (GP).
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'
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For depths beyond PP, we draw another diagonal to the
other end of GLand follow asim procedure.
ilar
W cantransfer these depth m asurem and
e
e
ents
est ablish a sim grid along one or both receding
ilar
sidewalls, as well as onaceilingor overhead plane.
• Afractional distance point m be used if the drawing
ay
surface is too sm to accommodate the normal
all
distance point. Ahalf-distance point w cut off twoill
foot increm s indepth for every one-foot increm
ent
ent
1 DP = 1 (SP - C) in plan.
in widt h: /2
/2
PERS CTIVE DRAW INGS / 103
PE