Example GeGeDe Application

This package provides an example illustrating how to use the GeGeDe package to author geometry description.

Setting up your package

To start off on the right foot, write your geometry description as a Python package. This section outlines how this very package is put together.

$ mkdir gegede-example
$ cd gegede-example
$ mkdir ggdex
$ emacs setup.py ggdex/__init__.py ggdex.cfg

This primes the package with:

setup.py

used to build a Python package from this source area

ggdex/__init__.py

initially empty, primes the package, will hold builders

ggdex.cfg

initially empty, will hold GGD configuration

Create a GeGeDe development environment and add your package in like so:

$ python setup.py develop
$ python -c 'import ggdex'
$ echo $?
0

That second command should quietly succeed. You are now setup so that any development on your code will be reflected “live” in your Python setup.

The builders

The example this package provides is very simple. Together they create a box-shaped world and inside that a 3x3x3 Rubik’s Cube. All builders live in ./ggdex/__init__.py. There are three builder classes:

WorldBuilder

This builder makes a cubic box. This can be used as a top-level “world” builder. It takes these configuration parameters:

material

the name for the material to use for the world

size

a (full) size for the world box

RubikBuilder

This builder is an example of a compound builder which builds some geometry directly and delegates more building to sub-builders. It does not directly create the sub-builders (although that is allowed) and instead relies on the user providing the configuration to give it the required sub-builders. Because of this indirection there is a contract made between this builder and any sub-builders w.r.t. what they provide. This particular builder expects three sub-builders, each returning one “type” of Rubik’s block in order: corner, edge and center.

Note, this is all contrived. It’s both more complex and to simplistic than required to describe an actual Rubik’s cube.

This builder takes these configuration parameters:

material

name of material to make the overall box from

gap

a buffer between blocks when placing them

RubikBlockBuilder

This builder makes one of the block 3x3x3-1 blocks that make up a Rubik’s cube. It allows satisfying the contract described above. It takes these configuration parameters:

location

a description of the block location taking values (corner, edge, center)

material

the material to use to make the block

size

the (full) size of the cube block

The configuration

A configuration which uses these builders is given in ./ggdex.cfg. There is one section for each instance of a builder. The world builder is first by convention (can be overridden) and sets a non-default value for material. It sets a sub-builder that of the overall Rubik’s cube. That builder then has three sub-builders each of which name on of three instances of the same builder type RubikBlockBuilder. The three instances are differentiated by their different location parameter. Care is taken in ordering these instances. See comments in the RubikBuilder.construct() method in ./ggdex/__init__.py.

Generating and exporting

The command line interface to GeGeDe can be used to generate geometry and to export it to some file.

$ gegede-cli -o ggdex.gdml ggdex.cfg

Another example: ggdex02

The ggdex02 directory and configuration file shows an alternate arrangement where each builder is placed in a separate module file. This example builds a simple layered scintillation detector, and includes examples for defining a wider range of elements, isotopic mixtures, and mixed materials. It also shows how to add parameters to logical volumes that will be used to fill

<auxilliary auxtype=key" auxvalue="value" />

in GDML. The ggdex02 example is run using

$ gegede-cli -o ggdex02.gdml ggdex02.cfg