Procedural surface

In computer_graphics, a procedural surface is a representation of a surface as a mathematics implicit equation rather than one which satisfies an explicit representation. An explicit representation is one which describes a line as the straight segment going through two given points. A procedural surface is one which is defined as a procedure. For example, in CAD/CAM milling applications, an offset surface is an procedural representation because it is defined as the surface which is a fixed distance from another surfaces. Another well known procedural edge on a 3D body is the silhouette edge. This edge is defined as the collection of points on a surface whose outwares surface normal is perpendicular to the view vector.

Another example is a blob as used in movies like The Abysis. The surface is defined as a surface which exists when two or more control points are oriented in such a way as to make the contribution potential exceed a certain threashold. This approach is commonly used by structural chemists and was defined by Van-der-Vaals when defining a region of space where the electric charge equipotential surface had a distinct value.