Call a parameter by its name in the ZOS-API

  • 8 December 2021
  • 4 replies

Userlevel 6
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When dealing with non-Standard surface types, you typically have access to extra parameters that are specific to that surface. For example, the Coordinate Break surface provides inputs for Decenter X, Decenter Y, etc.


Coordinate Break surface type with the extra data parameters highlighted

To access these parameters in the API, our sample code offers two options:

  1. Access a parameter based on the parameter number. A typical command for this may look like the following: decenterX = TheSystem.LDE.GetSurfaceAt(1).GetSurfaceCell(ZOSAPI.Editors.LDE.SurfaceColumn.Par1).DoubleValue;
  2. Access a parameter based on its column number. A typical command for this may look like the following: decenterX = TheSystem.LDE.GetSurfaceAt(1).GetCellAt(12).DoubleValue;

In both of these cases, you will need to have prior knowledge of the location in the LDE of the parameters you want to change. Or you will need to query the “Header” of the column you’re working with to confirm the parameter is correct. 

There is a third surface-specific method for calling parameters by their title. This method utilizes the ISurface interface within the LDE namespace. The steps for accessing this are below:

  1. Access a surface with the GetSurfaceAt property
  2. Access the ISurface interface with the SurfaceData command
  3. If needed, cast to the ISurface interface with the interface of the surface type (required for C#, not required for Matlab or PythonNET)
  4. Call a parameter from this interface. This allows you to call with the name “Decenter_X” instead of with a column or parameter number.

The commands for surface-specific parameters are found in the corresponding ISurfaceXXX interface within the LDE Namespace:


Screenshot from the ZOS-API Syntax Guide LDE Namespace page directing to the ISurfaceCoordinateBreak section. 


Below, I am providing examples in some of our supported languages. 

Python .NET

surf1 = TheSystem.LDE.GetSurfaceAt(1)
surfData = surf1.SurfaceData
surfData.Decenter_X = 10



    surf1 = TheSystem.LDE.GetSurfaceAt(1);
    surfData = surf1.SurfaceData;
    surfData.Decenter_X = 20;



using System;
using ZOSAPI;
using ZOSAPI.Editors;
using ZOSAPI.Editors.LDE;



            ILensDataEditor TheLDE = TheSystem.LDE;
            ILDERow surf1 = TheLDE.GetSurfaceAt(1);
            ISurface surf1Data = surf1.SurfaceData;

            // We must cast to the specific surface interface from the ISurface interface
            var coordBreakParams = (ISurfaceCoordinateBreak)surf1Data;


            coordBreakParams.Decenter_X = 30;
            double decenterXVal = coordBreakParams.Decenter_X;




4 replies

Userlevel 7
Badge +2

Hi Allie,


This is excellent. I already love the third method, it’ll be so much more convenient to work with parameters now.

Thanks for sharing!

Take care,



Userlevel 7
Badge +2

Hi Allie,


I hope you are well.

I was just going to try your third method for the first time, and it seems it might require casting with Python on my end.

This piece of code (Python 3.8.15, Pythonnet 2.5.2):


Returns the Tilt About X of a Coordinate Break surface (at least it works for me). However, this other piece of code:


Returns an error:

AttributeError: 'ISurface' object has no attribute 'TiltAbout_X'

Am I doing something wrong? If not, does it mean one needs to cast ISurface to ISurfaceCoordinateBreak, and if so, how would you do it?

Thanks for your help and take care,



Userlevel 6
Badge +2

Hi David,

Apologies for the delayed response. I’m going through my email inbox and saw that I missed the notification for this post.

I tested your code in Python 3.8.10 with Pythonnet 2.5.2 and it worked fine, as shown below:



Have you re-tested since you first messaged? And can you confirm that surface 11 in your file is a Coordinate Break surface?

Userlevel 7
Badge +2

Hi Allie,


I’ve tried it again today, and it works! I’m fairly sure my Surface 11 was a coordinate break because the GetCellAt(14) method was returning the right value so I don’t know what I did wrong at the time, but thanks a lot for your help and take care,