Oldal 103 [103]
REFLEXIONS IN RIPPLED WATER :7
for any given receding line is the point where the line from
the eye parallel to it meets the picture plane. It will be
found that the projections on to the picture plane of lines in
the ground plane radiating from a point vertically below
the eye are vertical lines. This is illustrated in Fig. 19.
The spectator is here supposed to be stationed above the
water and to be looking directly at the bridge to the right
of the diagram. E marks the position of his eye or “sta¬
tion point,” A B C D represents his “ picture plane,” with
the projection of the bridge as it appears to him, o being
the " centre of vision,” Eo the “direction of vision,” and
H the horizon line. EX is a perpendicular drawn from E
to meet the “ground plane” (surface of the water) in X.
L,, L,, etc. are lamps on the near side of the bridge, and
F,, F,, etc., are points on the surface of the water vertically
beneath these lamps. The streaks of light on the surface
of the water caused by these lamps will appear to one
looking from E to lie along the straight lines X F,, X F,, etc.,
which radiate from the point X immediately beneath his eye.
But the projection of these radiating lines on to his picture
plane will be vertical, and therefore parallel, lines. Let the
lines XF,, XF,, etc., cut the base of the picture plane (or
“sround line”) in the points g;, g, etc. From these points
draw perpendiculars g, 4,, g2 Aa, etc., to meet the horizon line
of the picture in 4,, A, etc. Then the lines EX and 4,3;,
being vertical, are parallel to each other; and since the plane
containing E and the horizon is parallel to the ground plane,
these lines, EX and 4,g,, are also equal. Therefore EX, is
parallel to Xg,; and therefore, by the well-known law of
perspective, 4, is the vanishing point for the line XF,. Simi¬
larly it can be shown that 4, is the vanishing point for XF,,
ha for XF,, and so on. Thus in the picture the streaks of
light are represented by the vertical lines /, £1, /2 £a/s 23 etc.
In “Modern Painters”* Ruskin makes reference to a
picture by Claude, in which the artist has fallen into an error
‘ Vol. I, Part II, Sec. V, Chap. I, § 17.