Feedback from Thomas Braunroth

[KeithSloan]

Hi Keith,

thanks again for helping me out. I was able to use your addon all day long and would like to give you some feedback.

Just to give you some background: During the last years I was, amongst others, interested in using atmospheric muons for imaging purposes, mainly to evaluate if this method can (and to which extent) be used to inspect the inventory of dual storage casks (spent fuel assemblies from nuclear reactors). All simulations I've done so far were with GEANT4 but since we now want to use a broader code-basis I decided to use GDML so that it's easier to share/use the geometry with other codes such as FLUKA. Long story short: I spent the day with reproducing the geometry of a specif cask in FreeCAD/GDML. Based on this, here's my feedback

• I only found one thing that didn't appear right to me: The symbol for cone looks more like a polyhedra than a cone.

• If someone were to ask me which basic geometric shape I miss the most, it would be G4Polycone (arbitrary number of layers). In my experience this shape is super-helpful.

• For the modelling of a typical dual-purpose cask, boolean operations (especially for cutting purposes) are needed a lot. It'll be really helpful if there's a way to subtract multiple objects within one step. If I see it correctly, so far it's only possible to perform binary operations.

Your tool was very helpful so far, I really like that it's embedded in FreeCAD.

Kind regards,

Thomas

[KeithSloan]

Munther's Comments

For multiple subtractions I have two suggestions that may help for the time being: (1) FreeCAD offers, and we do implement, the construction of Sketch Extrusions. Inside curves, bounded by an outside curve get subtracted from the extrusion. So, for example, if you constructed in the Sketcher a rectangle inside of which were multiple circles/squares/whatever and extruded the sketch, you will build a box with the with cylinders/other boxes subtracted from it. (2) Obviously the above is not general enough. For more general multiple shape subtractions, you can make use of the fact that FreeCAD allows MULTIPLE entities to enter a union. So you can select all the shapes you want subtracted from another shape, put them in a single union and then subtract that union from the object you want the multiple from. That will achieve what you want, but with ONE extra step, the creation of the union. That would still be much faster than doing multiple subtractions.

Again, we appreciate the feedback.

Munther

[KeithSloan]

For G4polycone

As a possible interim I have created a new branch PolyCone ( icon currently is just an 'X' )

If you click on it it offers a dialog where you can enter

Number of Planes
Start and increment values for r and z

On Okay this will create a GDMLPolyCone with the required number of rzpoints with initial r and z values

You can then always go to an rzpoint and change the r and z values in the Property editor.

Keith

[KeithSloan]

As pointed out by Munther, it should be easier to create a polycone using a revolved Sketch. The Part Sketch and Revolve facility are made available in the GDML workbench tool bar. You could create a sketch in the x-z plane and revolve it around the z-axis. This would be especially helpful, if, for example, you wanted to revolve a smooth curve around the z-axis. The GDML workbench, in fact, exports the surface as a polycone, but you would not have to enter the potentially hundreds of z planes manually. Again, documentation and examples are shown on Workbench's GitHub Wiki pages https://github.com/KeithSloan/GDML/wiki#revolved-sketches

[KeithSloan]

"I only found one thing that didn't appear right to me: The symbol for cone looks more like a polyhedra than a cone."

The initial icons were created by Jim Austin and my guidance was to use the images of the solids in the Geant4 User Guide
so