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inking, it will be well to
ings also. This, of course, is not a necessity in the making of good drawings, at the same time it is of much value. A knowledge of the subject should be possessed by one who takes up drawing, and having it in his possession, he can use it or not, according as he deems best.
Shading is used to set off a drawing, and to make it clearer than can be done with the plain work such as we have used up to this point. It gives character to the drawing, and makes it more attractive. From the manner in which the shading appears, it can be told at once whether a certain part of the drawing represents a projection or a hole in the object illustrated. Thus in Fig. 58, the shading of No. 1 shows that it is a solid piece, a rectangular block for instance. Now, referring to No. 3 of the same sketch, Q, R, S, T represents a rectangular figure of the same size and shape as No. 1, but shaded in a different manner. This shading shows us at once that Q, R, S, T is
R a rectangular hole cut in the block M, N, O, P, the latter being of course shaded in the same manner as No. 1.
Exactly in the same way, No. 2, shows by its shading a tee-shaped figure, and No. 4, by its different shading, shows a hole cut in the shape of a tee in the block U, V, W, X.
Also, in Fig. 59, No. 2 shows the end of a solid cylinder, and No. 3, by the difference from No. 2 in shading represents a cylindrical hole bored into the end of the block R, S, T, U.
Light and shade is naturally dependent upon the manner in which the rays of
light fall upon an object, and in order to make the shading of drawings consistent and systematic, the rays of light must always be considered as coming from a given direction, and after determining upon the direction in which they are to come, it should not be changed.
On this work, light may be assumed to come from the upper left hand corner of the drawing board, parallel with the sur. face of the board, and at an angle of 45 degrees with the horizontal and vertical lines of the drawing.
These rays of light are represented by the arrowheads of Nos. 1 and 2 in Figs. 58 and 59.
Any surface which these 45-degree lines strike is a light surface, and one which they do not strike is a dark surface. The line of intersection of two light surfaces is a light line, and not shaded, but the line of intersection of a light and a dark surface, or of two dark surfaces should be shaded.
Lines in the drawing which are drawn at 45 degrees and parallel with the rays of light are never shaded.
Referring again to No. 1, of Fig. 58, it will be seen that light strikes the lines A B and AC, which are therefore light lines, but because the object itself presents an obstacle to the further passage of light, the lines B D and C D are dark, and therefore shaded. In the same way we can account for the light and heavy lines in No. 2. In No. 2 it will be observed that the arrowhead passing through the corner G would strike the line H K at Y. It will be asked why H K is not shaded above Y, as the lines of light do not strike it. According to what we have said on the subject, this should follow, but it will be seen that a line partly heavy and partly light would not look well, and, therefore, for the sake of preserving the system, a line of this kind and in such location is made light.
Another contradiction arises of a simi. lar nature, in connection with Nos. 3 and 4.
It would rightly be argued that owing to the wall or shell surrounding the hol no light would strike the lines representing the rectangular hole, and therefore all four of those lines should be dark.
1 of Fig. 59, the same difficulties or apparent contradictions arise that we have already mentioned. In such a case as this, in order to preserve the uniformity of the system, each branch must be considered entirely by itself, and then there will be no trouble.
In this figure, the lines AO, BO, CO, and D O, also the four lines, EO, FO, GO and H O are drawn at 45 degrees. The first four are drawn parallel to the direction of the rays of light, and are therefore not shaded, but in the case of the latter four, although drawn at 45 degrees, they are not parallel to the rays of light, and should therefore be treated as any other lines would.
In the case of the shading of circles, the reasoning is no different from that followed in the shading of straight lines. Those rays that strike the circle on a tangent determine the points at which the shading should begin. In shading a circle, draw in the light circle first, then with the same radius take a new center at an angle, of 15 degrees from the first center, the distance between the two centers determining the width of the shade line at its widest point.
In No. 2, the second center is taken above, and in No. 3 below the first center. In putting in the second circle, use the same size of line as in the first, and fill in the space between them. In Fig. 60 we give exercises in shading, which will serve to show how the principles which we have discussed above, are applied on the shading of plumbing drawings.
In putting in the shade lines, they are usually drawn heavy at the outset, but it may possibly be easier for beginners to ink their drawings in the usual way, and then go over the lines to be shaded afterward, making them several times heavier than the light lines. If those who do not take up the inking care to do so they may shade their pencil drawings by using on the heavy lines a very soft pencil.
In inking shaded drawings it is custa mary to put in the light horizontal lines first, then the heavy lines, and so with the vertical lines. This method will save the trouble of changing the adjustment on the pen so frequently, and will result in more even work.
method followed in Nos. 3 and 4. Comparing Nos. 1 and 3, it will be seen that lines shaded in the one are light in the other, also in the case of Nos. 3 and 4. In No.
It will be found that very often a drawing will look better if the finer work, such as the supply pipes, etc., are not shaded, only the fixtures and larger conDections being thus treated.
In Fig. 61 we give the elevation of the
plumbing system for a cottage house, the work being shaded. This is the first complete elevation that we have given as an elevation, but we believe that those who have followed foregoing instructions will have no difficulty in making this drawing.