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Experimental setups, as complex as the LEP
detectors, can be described
rather accurately through the definition of a set of volumes.
Each volume is given a name and is characterised by:
- a shape identifier, specifying one of the basic
geometrical shapes available [GEOM050];
- the shape parameters, giving the dimensions of the volume;
- a local reference system, with origin and axes defined
for the each shape;
- the physical properties, given by a set of constants describing the
homogeneous material which fills the volume ( [CONS]);
- additional properties, known as tracking medium parameters,
which depend on the characteristics of the volume itself (the
material identifier is one of the constants) and on its geometrical and
physical environment (properties of the neighbouring volumes, magnetic field,
etc.) [CONS, TRAK];
- a set of attributes, in connection with the drawing package
and the detector response package [DRAW, HITS].
Until it is positioned in a given reference frame,
a volume is an entity which has no spatial relation with the other volumes.
By convention, a unique initial volume has to be defined first
which will contain
all the other volumes. The reference frame intrinsic
to this volume is considered to be the master reference frame.
There are sixteen basic shapes in GEANT, which are described in
[GEOM050].
Janne Saarela
Mon Apr 3 12:46:29 METDST 1995