Modifying RIS Element Spacing (In Proportion to the Wavelength λ) from Sionna Source Code
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This tutorial explains how to modify the RIS element spacing from the default value of λ/2 to a custom value proportional to the wavelength λ by directly editing the Sionna source code.

.. note::

   Sionna ray-tracing tool does not provide a direct way to modify the RIS element spacing via its standard interface.  
   However, it can be changed by manually editing the source code.

.. warning::

   Before making any changes, it's important to create a backup of the original `ris.py` file.  
   This allows you to easily restore it if needed.

1. **Locate the `ris.py` File**

   - Navigate to the following path where the Sionna ray-tracing source files are located:

   ``C:\Users\your_user_name\AppData\Local\Programs\Python\Python311\Lib\site-packages\sionna\rt``

   - Open the file `ris.py` for editing.

2. **Modify the RIS Element Spacing**

   Apply the following changes inside the `ris.py` file:

   - **Search for**:

      ``wavelength/tf.cast(2,``

      (You should find three matches.)

      **Replace all occurrences with**:

      ``wavelength/tf.cast(x,``

      where **x** is the new denominator so that the element spacing becomes **λ/x** instead of **λ/2**.

   - **Search for**:

      ``tf.cast(0.5, self._rdtype)``

      (You should find three matches.)

      **Replace all occurrences with**:

      ``tf.cast(1/x, self._rdtype)``

3. **Save and Restart**

   - Save the modified `ris.py` file.
   - Restart your Python environment to ensure that the changes take effect.