User Manual 3.4.1 Facets

Definition

A facet is a surface defined by its area and a normal vector, no supposition made of its exact shape.
From those information, it can compute its cross section seen from any incidental vector.
A facet is visibile only from one half-space : the cross section computed is not null only if the dot product with the incidental vector is negative.

It shall be used to describe a spacecraft geometry in cross section computations for force models.

Implementation

This class implements the CrossSectionProvider interface (org.apache.commons.math.geometry.euclidean.threed).
Please refer to the Javadoc for a complete list of public methods.

Instantiation

The Facet class is built from its area and normal vector :

Vector3D normalvector = new Vector3D(1.0, 5.6,-3.2);
CrossSectionProvider facet = new Facet(normalvector , 5.0);

Usage

The Facet class proposes basic methods to get its area and normal vector.

It also provides the method getCrossSection (CrossSectionProvider interface), that shall be used this way :

Vector3D incidentialBeam = new Vector3D(7.0,-2.0, 8.0);
double crossSection = facet.getCrossSection(incidentialBeam);

The result is not null only if "incidentialBeam " dot product with "normalvector " is negative.