Boolean Solids Example

This example demonstrates GEMC boolean solid operations. It builds three placed solids from unplaced component volumes: a plate with a subtracted hole, a cross made from a union, and a lens made from the intersection of two spheres.

Quickstart

Copy the example to your current directory. To create the geometry and run 10 events:

cp -r $GEMC_HOME/examples/basic/boolean_solids .
cd boolean_solids
./boolean_solids.py
gemc boolean_solids.yaml -n=10

Geometry

The geometry is defined in boolean_solids.py.

The world (a box named root) contains three visible boolean volumes:

The component volumes use the special material Component. They define the operands of the boolean expression but are not placed as visible detector volumes. The resulting boolean volumes are placed like any other GVolume, with their own material, color, position, and rotation.

Interactive viewer:

Boolean Expressions

A boolean solid is selected by assigning solidsOpr:

plate.solidsOpr = 'plate_box - plate_hole'
cross.solidsOpr = 'bar + bar_rotated'
lens.solidsOpr = 'sphere_one * sphere_two'

The first operand is evaluated at its own origin. The second operand uses its own position and rotation relative to the first operand. For example, plate_hole is shifted by 30 mm before it is subtracted from plate_box, so the hole is off center.

Generator

The particle kinematics are defined in the YAML file:

gparticle:
  - name: e-
    p: 500*MeV
    theta: 90*deg
    vx: -40*cm
    delta_vx: 12*cm
    randomVertexModel: uniform

See also the Internal Generator Documentation for more information.

Usage

Building the detector

Use the Python script boolean_solids.py to build the detector. By default, the setup is stored in a SQLite file named gemc.db.

./boolean_solids.py

See also the Building Geometry for more information.

Running GEMC

The file boolean_solids.yaml can be used to run the setup. Add -gui to run interactively:

gemc boolean_solids.yaml -gui

Running Events