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CAD to MCNP Conversion

The Visual Editor can read a 2D CAD dxf file or a 3D SAT file and convert them to an MCNP input file.


Use of this tool is taught as a special topic in several Visual Editor Classes:  Click Here

Current Status

Our final report on the CAD conversion work may be downloaded here. (vised_cad_mc2005.pdf File Size = 4.4 Meg): Click Here.

A paper was presented on this work at the Monte Carlo 2005 Topical Meeting, April 17-21 in Chattanooga, Tennessee.  Download the presentation here.

Sample Exercises

3D CAD Import of a Cube

Import an AutoCAD SAT file of a cube.

To download the instructions in a .pdf file, Click Here.

To download the SAT file, cube.sat Right Click Here and select Save Target As....


3D CAD Import of a More Complex File

Import an AutoCAD SAT file of a gazebo with a tree.

To download the instructions in a .pdf file, Click Here.

To download the SAT file, gazebo.sat Right Click Here and select Save Target As....


2D CAD Conversion

The 2D conversion works for most of the CAD geometric entities including, lines, polylines, multilines, circles, arcs and ellipses and also works for the insertion of blocks.  These geometric entities include most of the 2D geometries that can be created by CAD.  The Visual Editor will display these geometric entities and allow the user to select any of these items and remove them from the geometry (by scanning them and selecting the Delete button) before converting them to MCNP.   This can be done either before or after segmenting the surfaces.  The Visual Editor will also allow the insertion of an upper and lower surface to bound the 2D geometry in the axial direction.


This CAD conversion process has been tested on complex 2D CAD files.  The Figure below shows an example 2D CAD file that has been converted to MCNP.  The original CAD file is shown in the left plot window and displayed using the new Visual Editor CAD plotting capabilities.  The converted MCNP file is shown in the right plot window.  The original CAD file contains lines, polylines, polygons, multilines and circles.  The resulting MCNP geometry has 88 surfaces and 31 cells.  The first few lines of the resulting MCNP input file can be seen in the input window at the bottom of the figure.

CAD file, before and after

Click the image to open a larger picture.

3D CAD Conversion

The following SAT versions are supported: 4, 7, 8, 11, 14.


The 3D conversion has been broken down into two different types of conversions.  The first conversion algorithm handles solids that are entirely contained inside each other or sharing a common face.  This is the type of geometry that would be created if the CAD program is being used as a front end to generate the MCNP geometry.  The Visual Editor will then do the needed subtractions or unions in creating the MCNP geometry. 


The second conversion algorithm consists of a fully defined solid geometry model where all space is defined.  The CAD files of this type are often developed for manufacturing or simulation packages, without any consideration for the MCNP geometry constraints.

Prior to converting a CAD geometry, a 3D image of the geometry is displayed.  The user can move around the geometry using the mouse (rotate, pitch, yaw, roll) and can change the visibility of individual cells. 


This Figure shows an example of a CAD SAT file that has been read and is being displayed with some of the cells made transparent.  Details concerning the SAT file are shown in the right side of the Figure, where each body displayed is identified.  When the user clicks the mouse on a body in the plot window, the selected object will be identified in the panel on the right.


The user can rotate the 3D image and move around the object as desired.  In the Figure, the roof of the building has been made transparent to allow the user to see inside the building. 


Click the image to open a larger picture


For class dates and availability, see our training page.  This class will use CAD as a graphical interface for creating an MCNP geometry.  TurboCad will be provided for the class.  If you are skilled in using a different CAD package (e.g. AutoCAD, etc...) that is able to export .DXF and .SAT files and can bring a laptop with that software loaded, you may use your own CAD package.


The class will be taught with the latest beta version of the Visual Editor software.  Students will be provided with a copy of the beta version to take home if they bring proof that they own a valid copy of the current RSICC release.


The class is intended for MCNP users interested in using CAD as a front end for creating their geometry.  The first day will cover the basics of using the Visual Editor and creating some very simple CAD geometries that illustrate the conversion process.  The second day will deal with modifying existing CAD geometries so that they can be converted to MCNP.  Students should already have some familiarity with MCNP before taking this class.


The Figure below shows an example of a CAD geometry (shown in Turbocad) that is representative of the type of geometry we will be creating and converting to MCNP in the class.


 Click the image to open a larger picture


This Figure shows the resulting MCNP geometry after it has been converted to MCNP.  Included in this Figure is a 3D representation of the geometry generated by the Visual Editor.  Also shown in the Figure in the bottom right is a list of the CAD bodies that were imported and in the bottom left is the MCNP input file that is generated.

  Click the image to open a larger picture.

How You Can Help

We are looking for input files to test the conversion on.  If you have a 2D dxf or a 3D sat file that you would like to convert to MCNP, please contact me.  In order to successfully convert the CAD file, you might need to make some additional modifications to the CAD file to conform to the conversion limitations. 


If you are interested in funding this work to help meet you specific needs, please contact Randy Schwarz.