light and shadow are sharply defined and positive. Oil sphere B, the modeling is very gradual with no sharp definition. The lighting on A is characteristic of sunlight or direct artificial lights that on B of light from the sky without direct sunlight on the object, or of the popular indirect or diffused lighting.
The difference in these effects must be taken into consideration by the artist. The whole pic-tine should have the effect of one or the other. If one thing casts a shadow, all things must cast shadows, ff one shadow is soft and diffused, all other shadows must receive the same treatment Otherwise consistency is lost, When the eifeel of a drawing is bad this may be the reason.
Figure I on pagr? 82 shows the ellipses of the form shadow and the cast shadow on the ground plane. Note the central ray through the middle of the ball to the middle of the cast shadow The ellipses are drawn in perspective. Figure 2 shows how a shadow may be projected to the ground plane when a sphere is in midair.
Cast shadows of course require perspective, which many artists fail to state correctly. With any east shadow we have tluee tilings to consider: first, the position of the light source; second, the angle of light; undf third, the vanishing point of the shadow on the horizon. If the light source is behind us, we get the angle of light from a point placed below the horizon on a perpendicular line dropped down through the vanishing point of the shadows. From this point we bring lines up through the ground plane to the object, The shadow is then located on the ground plane by drawing lines from the object to the vanishing point of the shadows. (Sec Fig. 4, page 84.) When the light source is in front of the object (Fig. 5, page 84), we establish a position of the light source, and, on the horizon directly beneath, a vanishing point for the shadows. We then draw lines from the light source down through the top comers of the cube. Then from the vanishing point of the shadows wo draw lines through the bottom corners of the Cube. The crossing of these two sets of lines in dicates the limits of the shadow on the ground plane, (See also page 85).
The shadow from a cone is simple to execute. Draw the line of the direction of the light through the center of this base Then divide the ellipse of the base accordingly. From the apex of the cone draw the angle of light to the ground plane. The point at which it meets the line of the direction of light is the point of the shadow. Connect this to the base of I he conc at the halfway points of the ellipse (see Fig, 1, page 84). Figures 2 and 3 show the lighting worked out with a different direction shown in Fig. 3.
Tlu? effect of looking into the light source with these planes worked out is shown on page 86. Page 87 shows the opposite effect — shadows receding, with the light source at the artist's back. The effect of a suspended artificial light is shown on page fi8. Hero the perspective principle is reversed, sincc the shadows vanish at a point on the ground plane dircctly under the light source. Theoretically they spread out to infinity and have liltle to do with the picture horizon. This is really a radiating point to give direction to the shadow contours. However, we still have the three necessary points of the triangle formed by the fight source, the angle of light, and the direction of the light.
Remember: when y On ttte looking into the light-
The angle of light is [he nearest point of the three and is located On the ground plane.
The vanishing point of shadows is on the hori-sion, directly under the light source. when the light behind yoit—
The angle of light is located below the horizon directly beneath the vanishing point of shadows.
The direction of light is the line from the vanishing point of the shadows to die object. Tin: sourcc, not being visible, is not shown, but the ¿ingle is used to point backward to the object, and not beyond it.
All points aroiind a contour register as a cast shadow, and you draw those contours on the ground pïane within a rectangle (see pagcS/).
light r ^office
Note that all shadows recede to the same vanishing point. The vanishing point of shadows falls on the .horizon directly below the light
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