Re: Problems with ARB geometry, will I use PLA !?

From: Alberto Fasso' <fasso_at_SLAC.Stanford.EDU>
Date: Thu, 24 Jun 2010 04:22:07 -0700 (PDT)

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Dear Antonello,

please keep the correspondence on the discussion list, don't send your
questions to me alone. I am forwarding your question with my answer to th=
e list.

My answer:

How can I tell you to describe the planes, if you don't provide the neces=
I told you that you need to input THE COORDINATES OF A POINT and the comp=
of a vector. You have given no information about a point, and an angle wh=
describes the inclination of the planes: with respect to which axis?

Anyway, assuming the axis is z, you will need to input:
0.7071067811865475 -0.7071067811865475 0.0 xxx yyy zzz

where xxx yyy zzz are the coordinates of a point on the plane
and 0.707.... are respectively sin(45) and cos(45)
Be careful, in the case of a 45 degree plane the sine and cosine of the v=
are also those of 45 degrees, but if the angle is different, you will nee=
to figure out the direction of the vector PERPENDICULAR to the plane.
This is just elementary trigonometry, nothing to do with FLUKA!

You can also choose the opposite vector:
-0.7071067811865475 0.7071067811865475 0.0 xxx yyy zzz

but then you need to change the + and - in the definition of the region.


On Wed, 23 Jun 2010, Antonello Carloni wrote:

> Dear alberto,
> the ARB in my geometry corresponds to a figure made out of two plane
> parallel to the coordinate axes and two planes which are at 45=B0 conn=
> the previous ones.
> Of course there is a top and a bottom plane.
> My question is: how to describe the planes that are at 45 in respct to=
> coordinate axes!?
> Thank you!
> On Mon, 21 Jun 2010, Antonello Carloni wrote:
>>> Dear ALL,
>>> hallo again,
>>> I am experiencing trouble with the implementation of the objects drw=
>>> an=3D
>>> d
>>> coloured in blac in the picture attache.
>>> They are what in the old Fulka were called"ARBS".
>>> But when using the ARB card Fluka does not draw them,
>> If you have followed the discussion I had on this discussion list wit=
h Joe
>> Confort:

>> and following,
>> you will know that I have strongly recommended to never use ARBs.
>> On the other hand, Joe has attached some drawings where ARBs were dra=
>> although there was a geometry error.
>>> So i decide to use Cards like PLA and XYP and YZP.
>> Good!
>>> No problems about the latter two ones but what about the definition =
>>> PL=3D
>>> A!?
>>> The manual just says:
>>> * 11. Generic infinite half-space. Code: PLA Each PLA is defined by=
>>> numbers: H_x, H_y, H_z (x, y and z components of a vector of arbitra=
>>> length perpendicular to the plane), V_x, V_y, V_z (coordinates of an=
>>> point lying on the plane). The half-space "inside the body" is that =
>>> which the vector is pointing (i.e., the vector points =3DF6utside").=
>>> definition extends over a single card in default fixed format, and o=
>>> two cards in high-accuracy body fixed format.
>> .........
>>> And so what do those vectors Hx Hy Hz when describing the plane?!
>> Those are not "vectors", but the components of ONE vector (i.e. the
>> projections
>> of a vector on the 3 coordinate axes.
>> One point and one vector define a generic plane without any ambiguity=
>> Notice that the magnitude, or length, of the vector is irrelevant. In=

>> general
>> I use a unit vector, so the H_x, H_y, H_z are just its direction cosi=
>> You can choose the direction of the vector as you like, but then you =
>> take it into account when you use the plane to "build" regions (you m=
>> decide which part of space you prefer to be "inside" the plane, and w=
>> "outside").
>>> For example , how to describe the 45=3DB0 XY Plane such as the A or =
B in
>>> the
>>> picture attached to this e mail!?
>>> Sorry to bother you all, i might be not so clever but the interpreta=
>>> is really arb ,-)
>>> Thank you!
>> I am sorry, your attachment was unreadable on my mailing system. But =
>> manual is extremely clear. You need to input 6 numbers: 3 coordinates=
>> a point on the plane (any point, provided it is on the plane!) and 3
>> components
>> of a vector perpendicular to the plane (any vector, provided it is
>> perpendicular to the plane!) What is "arb" in all this?
>> Kind regards,
>> Alberto

Alberto Fasso`
SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
Phone: (1 650) 926 4762 Fax: (1 650) 926 3569
Received on Thu Jun 24 2010 - 23:21:27 CEST

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