Using Geometry Tests in Bogus
Algorithm
Built into BgsApp (BgsFwkModule V00-03-18 or greater) is code designed to
test for geometry errors. It is based on generic geant4 testing code
in BgsG4Extension (V00-00-22 or greater) that uses the intersection of
solids with linear trajectories to uncover problems. For example,
consider the following:
Here we have a line intersecting some physical volume (large, black rectangle).
Belonging to the volume are four daughters: A, B, C, and D.
Indicated by the dots are the intersections of the line with the
mother volume and the four daughters.
This example has two geometry errors. First, volume A sticks outside its
mother volume (this practice, sometimes used in geant3, is not supported
in geant4). This can be noticed because the intersection point (leftmost
magenta dot) lies outside the mother volume, as defined by the space
between the two black dots.
The second error is that daughter volumes A and B overlap. This is noticable
because one of the intersections with A (rightmost magenta dot) is
inside the volume B, as defined as the space between the red dots.
Alternatively, one of the intersections with B (leftmost red dot) is
inside the volume A, as defined as the space between the magenta dots.
Each of these two types of errors is represented by a line segment,
which has a start point, an end point, and, alternately, a length.
Depending on the type of error, the points are most clearly recognized in
either the coordinate system of the volume, the global (BaBar) coordinate
system, or the coordinate system of the daughters involved.
Also notice that certain errors will be missed unless a line
is supplied in precisely the correct path. Unfortunately, it is hard to
predict which lines are best at uncovering potential geometry errors.
Instead, the geometry testing code uses a grid of lines, in the hope of
at least uncovering gross geometry errors.
More subtle errors could easily be missed.
Another difficult issue is roundoff error. For example, daughters C and D
lie precisely next to each other. It is possible, due to roundoff,
that one of the intersections points will lie just slightly inside the
space of the other. In addition, a volume that lies tightly up against
the outside of its mother may have an intersection point that just slightly
lies outside the mother.
To avoid spurious errors caused by roundoff, a rather generous tolerance
of 0.1 micron is used. At the moment, this tolerance is fixed, but if
you believe that some adjustment would be useful, let me know, and it can
be added.
Finally, notice that I made no mention of the possible daughter volumes
of A, B, C, and D. To keep the code simple, only the immediate daughters
of a volume are checked at one pass. To test these "granddaughter" volumes,
the daughters A, B, C, and D each have to be tested themselves in turn.
To make this more automatic, the geometry testing code has a recursive
algorithm that firsts test a target volume, and then loops over all
daughter volumes and calls itself.
For a complex geometry, checking the entire volume heirachy can be
extremely time consuming. You have been warned!
Usage
The geometry checking code in BgsG4Extension is implemented in class
BfmGeomTest belonging to package BgsFwkModule. To control testing, the following
tcl parameters have been added to the Bogus module in BgsApp:
- geomTestMother: (boolean) If "true",
the immediate daughter volumes of the BaBar mother volume are checked.
These are the daughter volumes that are commonly refered to as the
"subsystem mother" volumes.
- geomTestAll: (boolean) If "true", a recursive
check of all volumes in the entire detector are checked. Very time
consuming.
- geomTestMesh: (int) The size of the mesh of lines
used in the recursive test of volumes. To make sure that the recursive
test would not take hours, the default value is 20. For a more exhaustive
test, increase this value. Be careful, though: the CPU time will go as
the square of this value.
- geomTestSubject: (string list) Set this tcl parameter
to the name of any physical volume you wished checked. Make sure you use the
(case sensitive)
name of the physical volume (and not the name of the logical volume).
This tcl parameter may be set any number of times to check multiple volumes.
- geomTestAllSubject (string list) As in the above,
except each volume specified is tested recursively. The size of the mesh
used is controlled by the geomTestMesh parameter.
Here is an example:
module talk Bogus
#
# Test all subsystem mother volumes for problems
#
geomTestMother set true
#
# Test some specific volumes for problems with their
# immediate daughters
#
geomTestSubject set Dch
geomTestSubject set EMCA
geomTestSubject set DCO5_phys
#
# Test the SVT recursively, using a fine mesh
# Be prepared to wait!
#
geomTestMesh set 100
geomTestAllSubject set Svt
exit
The tests are run after the first event. If no problems are found,
there will be no output. Otherwise, you will get something
like the following for each error:
GeomTest Error: Overshooting daughter volume
The volume DCO5_phys[0] appears to extend outside the mother volume DCHO_phys[0]
at the following points in global coordinates: (list truncated)
length (cm) ---------- start position (cm) ----------- ----------- end position (cm) ------------
0.014002 -57.7882 -56.63 -124.38 -57.7742 -56.63 -124.38
0.0124996 -64.7325 -48.54 27.64 -64.72 -48.54 27.64
0.0109108 74.1461 -32.36 -110.56 74.157 -32.36 -110.56
0.0109108 74.1461 -32.36 96.74 74.157 -32.36 96.74
0.0102062 -79.2757 -16.18 -41.46 -79.2655 -16.18 -41.46
0.0100504 -80.5045 -8.09 110.56 -80.4945 -8.09 110.56
0.0100504 -80.5045 8.09 5.68434e-15 -80.4945 8.09 5.68434e-15
0.0115468 -70.073 40.45 -110.56 -70.0615 40.45 -110.56
0.014002 -57.7882 56.63 41.46 -57.7742 56.63 41.46
0.0115468 -40.45 -70.073 -124.38 -40.45 -70.0615 -124.38
0.0229355 72.81 -35.2864 -110.56 72.81 -35.2635 -110.56
0.0102062 16.18 -79.2757 -82.92 16.18 -79.2655 -82.92
0.0115468 -40.45 -70.073 -55.28 -40.45 -70.0615 -55.28
0.0229355 72.81 -35.2864 -41.46 72.81 -35.2635 -41.46
0.0102062 16.18 -79.2757 -13.82 16.18 -79.2655 -13.82
0.0115468 -40.45 -70.073 13.82 -40.45 -70.0615 13.82
0.0229355 72.81 -35.2864 27.64 72.81 -35.2635 27.64
0.0102062 16.18 -79.2757 55.28 16.18 -79.2655 55.28
0.0115468 -40.45 -70.073 82.92 -40.45 -70.0615 82.92
0.0229355 72.81 -35.2864 96.74 72.81 -35.2635 96.74
Which in the mother coordinate system are:
length (cm) ---------- start position (cm) ----------- ----------- end position (cm) ------------
0.014002 -57.7882 -56.63 -124.38 -57.7742 -56.63 -124.38
0.0124996 -64.7325 -48.54 27.64 -64.72 -48.54 27.64
0.0109108 74.1461 -32.36 -110.56 74.157 -32.36 -110.56
0.0109108 74.1461 -32.36 96.74 74.157 -32.36 96.74
0.0102062 -79.2757 -16.18 -41.46 -79.2655 -16.18 -41.46
0.0100504 -80.5045 -8.09 110.56 -80.4945 -8.09 110.56
0.0100504 -80.5045 8.09 5.68434e-15 -80.4945 8.09 5.68434e-15
0.0115468 -70.073 40.45 -110.56 -70.0615 40.45 -110.56
0.014002 -57.7882 56.63 41.46 -57.7742 56.63 41.46
0.0115468 -40.45 -70.073 -124.38 -40.45 -70.0615 -124.38
0.0229355 72.81 -35.2864 -110.56 72.81 -35.2635 -110.56
0.0102062 16.18 -79.2757 -82.92 16.18 -79.2655 -82.92
0.0115468 -40.45 -70.073 -55.28 -40.45 -70.0615 -55.28
0.0229355 72.81 -35.2864 -41.46 72.81 -35.2635 -41.46
0.0102062 16.18 -79.2757 -13.82 16.18 -79.2655 -13.82
0.0115468 -40.45 -70.073 13.82 -40.45 -70.0615 13.82
0.0229355 72.81 -35.2864 27.64 72.81 -35.2635 27.64
0.0102062 16.18 -79.2757 55.28 16.18 -79.2655 55.28
0.0115468 -40.45 -70.073 82.92 -40.45 -70.0615 82.92
0.0229355 72.81 -35.2864 96.74 72.81 -35.2635 96.74
Which in the coordinate system of DCO5_phys[0] are:
length (cm) ---------- start position (cm) ----------- ----------- end position (cm) ------------
0.014002 -57.7882 -56.63 -124.38 -57.7742 -56.63 -124.38
0.0124996 -64.7325 -48.54 27.64 -64.72 -48.54 27.64
0.0109108 74.1461 -32.36 -110.56 74.157 -32.36 -110.56
0.0109108 74.1461 -32.36 96.74 74.157 -32.36 96.74
0.0102062 -79.2757 -16.18 -41.46 -79.2655 -16.18 -41.46
0.0100504 -80.5045 -8.09 110.56 -80.4945 -8.09 110.56
0.0100504 -80.5045 8.09 5.68434e-15 -80.4945 8.09 5.68434e-15
0.0115468 -70.073 40.45 -110.56 -70.0615 40.45 -110.56
0.014002 -57.7882 56.63 41.46 -57.7742 56.63 41.46
0.0115468 -40.45 -70.073 -124.38 -40.45 -70.0615 -124.38
0.0229355 72.81 -35.2864 -110.56 72.81 -35.2635 -110.56
0.0102062 16.18 -79.2757 -82.92 16.18 -79.2655 -82.92
0.0115468 -40.45 -70.073 -55.28 -40.45 -70.0615 -55.28
0.0229355 72.81 -35.2864 -41.46 72.81 -35.2635 -41.46
0.0102062 16.18 -79.2757 -13.82 16.18 -79.2655 -13.82
0.0115468 -40.45 -70.073 13.82 -40.45 -70.0615 13.82
0.0229355 72.81 -35.2864 27.64 72.81 -35.2635 27.64
0.0102062 16.18 -79.2757 55.28 16.18 -79.2655 55.28
0.0115468 -40.45 -70.073 82.92 -40.45 -70.0615 82.92
0.0229355 72.81 -35.2864 96.74 72.81 -35.2635 96.74
Page author:
David C. Williams
| Last significant update: Jan-04-2001 |
$Id: GeomTest.html,v 1.1 2001/01/04 22:00:52 davidw Exp $ |
|
