FreeCAD Python GDML Workbench

FreeCAD's python Importer & Exporter for GDML files.

A GDML new structure workbench is available as https://github.com/KeithSloan/GDML and is installable via FreeCAD's AddonManager.

Found it difficult to keep two repositories upto date.

So people are advised to switch to the new repository.

https://github.com/KeithSloan/GDML

To upgrade to new structure workbench you will need to either do a fresh install of FreeCAD or delete the /Mod/GDML directory of your current installation.

Note: Sister project development https://github.com/KeithSloan/FreeCAD_Geant4

Prerequisites

• FreeCAD >= v0.18.3 (build that supports Python3)
• Python 3
• python3-lxml package
• git

Note: As I had to make a lot of changes to get things working with Python3 the development branch <workbench> has now been merged with the master branch

Installation

Linux and MacOS

As stated above, this WB requires python3-lxml
For example on Ubuntu or Debian derivatives you can install via:

apt-get install python3-lxml

• Invoke the following in the CLI

git clone https://github.com/KeithSloan/FreeCAD_Python_GDML.git
cd FreeCAD_Python_GDML
chmod +x softLinks

• Open softLinks in your text editor and check that the paths are correct.
• Run softLink script to soft link the module into FreeCAD and FreeCAD-daily systems

sudo ./softLinks

• Start or Restart FreeCAD

Windows

• Contents of Mod directory should be copied to a sub directory named GDML in the windows FreeCAD Mod directory this should include the sub directory Resources

• To instal lxml under Windows

  • Install pip
  • From the FreeCAD bin directory i.e. C:\Program Files\FreeCAD 0.18\bin
  • Run the command pip install lxml --user [username]
  • Start or Restart FreeCAD

Details of GDML

For more information on GDML see

GDML User Guide

GDML Solids

Usage

GDML Solids

GDML Solids are implemented as FreeCAD Python Objects and have the same properties as defined by GDML. By selecting an Object the properties can be changed via the FreeCAD properties windows and the resulting changes displayed.

Create a new GDML design

1. Start FreeCAD
2. Select the GDML workbench from the workbench dropdown menu.
3. Select File > New
   Result: This will load the default GDML File with materials and creates a World Volume.
4. Create 1-n Volumes in the World Volume by
   • Click on the Part icon (image: yellow blockish icon)
   • Drag the created Part to the World Volume in the Tree window
   • Part maybe renamed via right click context menu
5. Create GDML Solids by:
   • Clicking on the corresponding icon of the workbench.
   • Drag the GDML object to the appropriate Part again via the Tree window
   • You can then change the attributes by selecting the GDMLObject in the Tree window then changing the properties in the Property View

So a valid structure for a GDML file is:

• Single World Volume (Part)
• A number of Volumes (Parts) under the World Volume
• A number of GDML Objects can exist in one Part ( GDML Logical Volume)

6. To Export to GDML
   1. Select the 'World' Volume ( Default Name WorldVol )
   2. File export
   3. Select filetype as GDML ( Bottom Box of Export file window)
   4. Select Destination and file name with GDML as file extension

Important Notes:

• Opening a new file when the GDML workbench is active will load a Default file.
• The Default file is defined in GDML/Mod/Resources/Default.gdml.
• New GDML objects have the material set to SSteel0x56070ee87d10 i.e. the first material in the Default file.
• Other materials can be set by editing the material property via the FreeCAD parameters View of the Object after creation.

GDML Object Creation

Upon switching to the GDML workbench, one will notice a number of icons that become available on the Workbench bar.

• Clicking on one the icons will create a GDML object with default values.
• It should then be dragged to the appropriate Part (GDML Logical Volume)
• In neccessary, once can then edit the properties via the properties window. The parameters should be the same as in the GDML user guide.
• If the Object is part of a Boolean you will have to use the recompute facility of FreeCAD to see the change to the Boolean. This can be achieved through the right clicking on the context menu or clicking the Recompute icon in the toolbar.

GDML Objects Currently Supported

GDMLBox

Short decription

GDMLCone

Short decription

GDMLElTube

Short decription

GDMLEllipsoid

Short decription

GDMLSphere

Short decription

GDMLTrap

Short decription

GDMLTube

Short decription

GDML Import

On import or open of a GDML file a Dialog box will open with two options

• Import
• Scan Vol

Import will do a straight import of GDML Objects etc.

Scan Vol is for large files like Alice.GDML that take far too long to process.

Volumes are only processed to a limit depth i.e. volume names are determined but not processed For unprocessed volume the names are preceded by NOT_Expanded so an example volume name would be: NOT_Expanded_<VolumeName>

Expansion of Scanned Volume

Unexpanded Volumes can be expanded by:

1. Switching to the GDML workbench.
2. Selecting a volume in the labels & attributes window
3. Clicking on the experimental Expand Volume icon 'E'

On opening of a GDML file the appropriate FreeCAD implemented python Object is created for each solid

Viewing Volumes

The first icon on the workbench bar is different. If you select a object by one of the following methods

1. A volume via the Combo view - Model - Labels & Attributes.

   Then click on the icon it will cycle the display mode of the selected Volume and all its children. The cycle is Solid -> WireFrame -> Not Displayed -> Solid

2. In the main display - select a face by

   Then click on the icon it will cycle the display mode of the selected object

SampleFiles

SampleFiles directory contains some sample gdml files.

One in particular is lhcbvelo.gdml. This file takes a LONG LONG time to import/open, over a minute on my system, but does eventually load. On my system I have to okay one wait. When it finally does display you will want to zoom in.

If when it is displayed you go down the Volumes tree to VelovVelo under the World volume then click on the toggle icon ( 1st GDML icon in the workbench) Again wait patiently and the display will change to wireframe. You can then decend further down the Volumes tree, select one and again use the toggle icon and that volume and children will change to Solid. In this way various parts in different volumes can be examined.

GDML Objects Exporter

To export to GDML

1. Select the 'world' Volume, should be first Part in Design
2. File export
3. Select GDML as filetype
4. Make sure file has GDML as file extension

GDML Objects

GDMLObjects are output as straight GDML solids

FreeCAD Objects

The following FreeCAD objects are output as GDML equivalents

FreeCAD	GDML
Cube	Box
Cone	Cone
Cylinder	Tube
Sphere	Sphere

If not handled as above then objects shapes are checked to see if planar, if yes converts to Tessellated Solid with 3 or 4 vertex as appropriate. If not creates a mesh and then a Tessellated solid with 3 vertex.

Constants / Isotopes / Elements / Materials

Importing a GDML will create FreeCAD objects for the above and export should create the same GDML definitions as imported.

The Ability to change to change these maybe implemented in the future.

Preferences

There is now an option to toggle Printverbose flag to reduce printing to the python console.

New facility compound

Use of compound to facilitate preperation for FEM analysis

Usage

• Select a volume/Part i.e. the first Part which is the GDML world volume and click on the compound icon 'C'

  1. Create an object named Compound under the selected Volume
  2. Create an FEM Analysis Object.
  3. All the materials of the objects in the Volume/Part/Compound are added to the Analysis Object.

• You can then switch to the FEM Workbench (Finite Element Analysis) and proceed with an analysis which would include:

  1. Double click on each of the materials to edit their properties
  2. From the FEM workbench select the Compound Object and click on the icon to create a Mesh.
  3. Rest would depend on what analysis and what solver it is intended to use.

  Also as an experiment: thermal parameters have been added to the GDMLmaterial object so these could be changed before creating a compound. One option to be would be to add elements to GDML files to enable loading and exporting, but then they would NOT be standard GDML files (maybe a different file extension?)

Roadmap

• Handle different Positioning between GDML & FreeCAD
• Add support for quantity
• Add further GDML Objects
• Add facility to add Volume
• Add facility to edit Materials
• Add facility to edit Isotopes
• Add facility to edit Elements
• Tidy up softLink script
• Documentation
• Investigate handling of Materials
• Need to sort out AIR definition

Workbench

• Workbench Dialog for initial GDML Object values(?)
• Analyze FreeCAD file for direct conversion of object to GDML solid
• Display mesh for objects that will not directly convert
• Provide options to control meshing objects that will be Tessellated
• Icons to Analize and Export
• Make GDML an installable workbench

Note: For NIST Materials database see http://physics.nist.gov/PhysRefData

Acknowledgements

Graphic Icons

• GDML Shapes designed by Jim Austin (jmaustpc)
• Cycle icon by Flaticon see www.flaticon.com

Thank you also to:

• Wouter Deconnick

• Hilden Timo

• Agata Walukiewicz

• Elena Volkova

• FreeCAD forum members:

  • wmayer
  • Joel_graff
  • chrisb
  • DeepSOIC
  • ickby
  • looooo
  • easyw-fc
  • bernd

• OpenCascade Forum members:

  • Sergey Slyadnev

Future Development Road Map

• Workbench Dialog for initial GDML Object values(?)

• Handle different Positioning between GDML & FreeCAD

• Add support for quantity

• Add further GDML Objects

• Add facility to add Volume

• Add facility to edit Materials

• Add facility to edit Isotopes

• Add facility to edit Elements

• Workbench

  • Analize FreeCAD file for direct conversion of object to GDML solid
  • Display mesh for objects that will not directly convert
  • Provide options to control meshing objects that will be Tessellated
  • Icons to Analize and Export

• Tidy softLink script

• Make FreeCAD an installable workbench

• Documentation

• Investigate handling of Materials

For NIST Materials database see http://physics.nist.gov/PhysRefData

Need to sort out AIR definition

Graphic Icons

GDML Shapes designed by Jim Austin jmaustpc Cycle icon by Flaticon see www.flaticon.com

Thanks to

• Wouter Deconnick
• Hilden Timo

and the following FreeCAD forum members

• wmayer
• Joel_graff
• chrisb
• DeepSOIC
• ickby
• looooo
• easyw-fc
• bernd

OpenCascade Forum members

• Sergey Slyadnev

Feedback

Please report bugs by opening a ticket in the FreeCAD_Python_GDML issue queue

Note: I am always on the look out for test gdml files (small to medium size)XXXX# FreeCAD_Python_GDML

To contact the author via email: keith[at]sloan-home[dot]co[dot]uk