Computer representation of surfaces

The curves obtained by varying v while u is fixed are called the v flow lines.

Surfaces closed in one direction include a cylinder, cone, and hemisphere.

Moving in any direction on such surfaces will cause the observer to travel forever without hitting an edge.

Sheet metal surfaces which lack a flat pattern must be manufactured by stamping using 3D dies (sometimes requiring multiple dies with different draw depths and/or draw directions), which tend to be more expensive.

These surface patches are analogous to the multiple polynomial arcs used to build a spline.

To combine them back into a single entity, a skin or volume is created.

A skin is an open collection of faces and a volume is a closed set.

Skins and faces can also be offset to create solids of uniform thickness.

Sharp angles between faces built on different supports (planes or surfaces) are common.

In virtual reality and computer animation, an object may also be represented by a surface mesh of node points connected by triangles or quadrilaterals.

The triangles or quadrilaterals can each be shaded differently depending on their orientation toward the light sources and/or viewer.