Curving a surface
Cross section can be drawn on a surface toexplain or emphasize its curvature. They play a major role in determining how a shape is perceived. One can deaw lestimations of curved cross sections, or using a more precise approach, strat with a flat surface and partly elevate it or push it down. When the cross sections of the flat surface remain visible, the final curvature of the plane can be perceived in relation to these.