1st Grade Revolutions

When we move from 2D Shapes to 3D shapes we "extrude a profile". This means that we take a 2D image and pull it into a 3D volumetric shape. A real world example of an extrusion machine are Playdough sets we grew up with where the clay was pushed though a hole to extrude a particular shape. This most often was extruding a cylinder from a circular hole. 

Another type of extrusion is the revolve. Think about the cross-section of a bicycle tire which is mostly circular, but it is extruded in a torus (donut) shape around an axis (axle). The image below shows the transition in 1st grade yesterday from hand drawn 2D profiles to 3D revolutions of those shapes. 

Student drawn 2D profiles revolved into 3D shapes

Student drawn 2D profiles revolved into 3D shapes