. Free-hand drawing : a manual for teachers and students. Fig. 20. Perspective of a Sphere and Cube. ellipse will appear a circle, and the representation of the cubewill cause the same image in the eye that the cube does. Figs. 18and 20 are distorted because they are made on a vertical pictureplane through which the visual rays pass obliquely. Fig. 21 is a side view representing the sphere situated as in with a picture plane touching the sphere, and so inclined 86 FREE-HAND Fig. 21. A Side View. as to be perpendicular to a line from the spectators eye to the centreof the spher
. Free-hand drawing : a manual for teachers and students. Fig. 20. Perspective of a Sphere and Cube. ellipse will appear a circle, and the representation of the cubewill cause the same image in the eye that the cube does. Figs. 18and 20 are distorted because they are made on a vertical pictureplane through which the visual rays pass obliquely. Fig. 21 is a side view representing the sphere situated as in with a picture plane touching the sphere, and so inclined 86 FREE-HAND Fig. 21. A Side View. as to be perpendicular to a line from the spectators eye to the centreof the sphere. This line is the central visual ray and the axis of thecircular cone formed by the visual rays. Since this cone is inter-sected by a picture plane which is perpendicular to its axis, thesection of the cone—that is, the perspective or picture of thesphere — is a true picture of the object and is similar in its form tothe picture formed by the sphere in the eye. The picture of Fig. 21 is a circle, and differs from that of Fig. 18in a very important point ; for when Fig. 18 is correctly seen the eye must be at one fixed thus seen it createsin the eye a circular image,but the picture of Fig. 21may be seen from anypoint situated in a perpen-dicular to the pictureerected at its centre, andthe image produced in theeye will be a circle, without regard to the distance of the eye fromthe paper. We must decide that the drawing. Fig. 21, which represents thesphere by a circle
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Keywords: ., bookauthorcr, bookcentury1800, bookdecade1890, booksubjectdrawing
