surface_area - Function

Geometrical function


Description

Returns the area of a surface. Accuracy is controlled by an optional parameter.

Syntax

surface_area(surface, accuracy)

REF	surface;
FLOAT	accuracy;

Principal parameters

surface

- Identity of surface

Optional parameters

accuracy

- Maximum relative error. Default is 0.01 = 1 % , i.e.output error is less than 1 % of calculated area

Return value

A FLOAT value equal to the calculated area

Example

a:=surface_area(#4);

Calculates the area of a surface with ID = #4. Default numerical accuracy (1%) is used.

Comments

The area is computed by numerical integration. The number of calculations (iterations) is at least two. Smaller and smaller elements (triangles) are used in each iteration and the calculation is ended when the relative change of area between two consecutive iterations is less than the given accuracy, i.e. ( Change of area )/ ( Total area ) < accuracy. The maximum number of iterations is ten (10).