The Elements of Perspective

PROBLEM I.

Reading edition

PROBLEM I.

TO FIX THE POSITION OF A GIVEN POINT.[Footnote 8]

Let P, Fig. 4., be the given point.

Fig. 4.

Let its direct distance be D T; its lateral distance to the left, D C; and vertical distance beneath the eye of the observer, C P.

It is required to fix on the plane of the picture the position of the point P.

Join C T, cutting G H in Q.

From Q let fall the vertical line Q P′.

Join P T, cutting Q P in P′.

P′ is the point required.

If the point P is above the eye of the observer instead of below it, C P is to be measured upwards from C, and Q P′ drawn upwards from Q. The construction will be as in Fig. 5.

Fig. 5.

And if the point P is to the right instead of the left of the observer, D C is to be measured to the right instead of the left.

The figures 4. and 5., looked at in a mirror, will show the construction of each, on that supposition.

Now read very carefully the examples and notes to this problem in Appendix I. (page 69). I have put them in the Appendix in order to keep the sequence of following problems more clearly traceable here in the text; but you must read the first Appendix before going on.

Notes in this chapter

Note 1 · : More accurately, “To fix on the plane of the picture the apparent position of a point given in actual position.” In the headings of all th Note 2 · : The sentence within brackets will not be repeated in succeeding statements of problems. It is always to be understood.] Return to text Note 3 · : In order to be able to do this, you must assume the distances to be small; as in the case of some object on the table: how large distances Note 4 · [Let G H be the Sight-line, S the Sight-point, and T the Station-point.][Footnote 9]Note 5 · Arrange the three distances of the object on your paper, as in Fig. 4.[Footnote 10]