# Constructive Quadric Geometry

From: Steven Morrow <morrow_at_dosisoft.com>
Date: Thu, 08 Dec 2005 12:04:11 +0100

Hello,

I have a general question regarding a visualisation of geometries which I would like to do with ROOT. (Please excuse the length of this mail.)

I am a user of a Monte Carlo simulation code called PENELOPE
(http://www.nea.fr/abs/html/nea-1525.html). The geometry package of this
code uses quadric surfaces for the construction of the 3D geometry. This is different from ROOT, or GEANT or other codes that I've known before, which use solid primitives such as cylinders or boxes and then a 'Constructive Solid Geometry' (CSG) to combine these primitives to make more complicated shapes (Phys.Med.Biol. 46 (2001) 1163-1186).

The implicit equation for a quadric is:

F(x,y,z) = A*x*x + B*x*y + C*x*z + D*y*y + E*y*z + F*z*z + G*x + H*y + I*z + J = 0

which allows to draw planes, pairs of planes, spheres, cylinders, cones, ellipsoids, paraboloids, hyperboloids, etc.

My problem is to be able to visualise in 3D the geometries created by PENELOPE. I would like to create a ROOT application for this. (The visualisation codes provided with PENELOPE are fairly primitive.) For this I need a library that will allow me to draw a quadric surface (from its equation above) and then combine these quadrics in a 'Constructive Quadric Geometry'. The only code I have found which allows this is POV-Ray, however this renders the image very slowly and doesn't allow interaction with the mouse.

I like very much the graphics possibilities provided by ROOT and I would like to use it for this task. However ROOT doesn't have the possibility to draw quadrics. I see that openGL classes are being added to ROOT, however openGL doesn't seem capable of an intrinsic quadric either.
(Only specific cases such as cylinders or spheres can be rendered .)

I would have liked to contribute to ROOT by adding a class to permit the use of quadrics, but my programming skills are not up to the job and I don't know the internal workings of ROOT well enough to manage this.

Might quadric geometries be added to ROOT at some time in the future? Does anyone have any experience of using quadric surfaces for this purpose? Or know of an existing code which can do what I need now?

Regards,

Steven Morrow

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Received on Thu Dec 08 2005 - 12:04:58 MET

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