Ellipses:

An ellipse is a circle viewed from an angle. Looking across the face of a circle, it is foreshortened, and we see an ellipse. The axis of the ellipse is constant, and it is represented as a straight centreline through the longest part of the ellipse. The height is constant to the circle. See the image below to show how a circle is viewed as an ellipse and finally one can draw a wrist watch from an angular position known as perspective.

Fig.52: A circle easily can be transformed into a product.

Casting Shadows:

When there is only one light source (such as the sun), all the shadows in the picture are cast by that single source. All the shadows read from the same vanishing point. This point is placed directly under the light source, whether on the horizon line or more forward in the picture plane. The shadows follow the plane on which the object is sitting. Shadows also follow the contour of the plane on which they are incident.

Light rays travel in straight lines. When they strike an object, the object blocks the rays from continuing and creates a shadow relating to the shape of the blocking object. Given below is a simple example of the way to plot the correct shape and length of a shadow for the shape and the height of the light.

If the light is raised, lowered, or moved to the side, the shape of the shadow will change accordingly.

Fig.53. Casting shadows considering only one point of source of light.