Rotations, Spirals, and divisions with ellipses (Concept drawing)

Rotations for hinges can be accurately drawn using the techniques in my last post with ellipses drawn on surfaces by drawing along ellipses. Drawing a shape on any of the axis's presented by the ellipse can represent a door at any angle of the swing as an example.

To subdivide an ellipse, draw a half circle parallel to the ellipse drawn on a surface. Divide this half circle into even “pie slices” with a protractor or just eyeball it. Then, draw parallel lines through the intersecting points of the circle over to the vertical line of the ellipse, and then connect them to the other end of the surface following the vanishing point. Mark the intersection of the ellipse and the lines previously drawn and connect them to the center for perfect divisions on the ellipse. According to Scott Robertson, “being able to subdivide am ellipse will help with drawing things like spiral staircases, equally spaced links on a tank tread, hour positions on a clock, or teeth around a gear” (Robertson 16). These techniques are shown in this drawing of a gear that I drew. 

Question: What careers go with the style of concept drawing and drafting?  

Ellipses and Circles (Concept Drawing)

Drawing circles in perspective:

                Ellipse anatomy- An ellipse has a minor and major axis, the minor axis cuts the ellipse in half across its narrowest section, and the major axis cuts it on the widest section. When it comes to drawing circles in perspective, which turn into ellipses, the major axis should be ignored since it would almost never cross the actual center of the circle. The minor axis on the ellipse will always point towards the vanishing point to make a circle. This makes the minor axis like the axis to a wheel.

                Placing ellipses on surfaces- according to Scott Robertson’s rules, to draw an ellipse on a surface, “the minor axis is always perpendicular to the surface on which the circle will be placed” (Robertson 73). To place the ellipse on a surface, first draw a minor axis perpendicular to the surface edge, then draw an ellipse around the minor axis, then draw a box around the shape and match the angle of the ellipse up to the angle of the box, which should match with the shape of the surface this is all on. 

Basic shapes using ellipses on surfaces

                Where are some examples of where you could use this technique in a drawing?