8

Hedra Extended Primitive 183
Inter face
Fam ily group
Usethisgrouptoselectthetypeofpolyhedronto
create.
Tetra—Creates a tetrahedron.
Cube/Octa—Creates a cubic or octahedral
polyhedron (depending on parameter settings).
Dodec/Icos—Creates a dodecahedron or
icosahedron (depending on parameter settings).
Star1/Star2—Creates two different star-like
polyhedra.
Tip: You can animate between Hedra types.
TurnontheAutoKeybutton,gotoanyframe,
and change the Family check box. There is no
interpolation between types; the model simply
jumps from a star to a cube or tetrahedron, and
so on.
Family paramete rs group
P, Q—Interrelated parameters that provide a
two-way translation be tween the vertices and
facets of a polyhedron. They share the following:
• Rangeofpossiblevaluesis0.0through1.0.
• The combined total of the P and Q values can
be equal to or less than 1.0.
• Extremes o ccur if either P or Q is set to 1.0; the
other is automatically set to 0.0.
• Midpoint occurs when both P and Q are 0.
In the simplest terms, P and Q change the
geometry back and forth b etween vertices and
facets. At the extreme settings for P and Q,
one parameter represents all vertices, the other
represents all facets. Intermediate settings are
transition points, with the midpoint an even
balancebetweenthetwoparameters.
Axis Scaling group
Polyhedra can have as many as three kinds of
polygonal facets, such as triangle, s quare, or
pentagon. These facets can b e regular or irregular.
If a polyhedron has only one or two types of facet,
only one or two of the axis scaling parameters are
active. Inactive parameters have no effect.
P, Q , R —Controls the axis of reflection for one of
the facets of a polyhedron. In practice, these fields