Konstantin Klementiev

That example already has a [description](https://xrt.readthedocs.io/gallery3.html#defocusing-by-a-distorted-mirror). Which aspect you don't understand?

```b4c = rm.Material(('B', 'C'), quantities=(4, 1), rho=2.52)``` https://xrt.readthedocs.io/raycing.html#xrt.backends.raycing.materials.Material

You can use PolygonalAperture. It needs a sequence of (x, z) pairs that define the opening(s). I've added a test `tests/raycing/test_polygonal_aperture.py` where you can find an example of a grid...

For pure GUI users, I've now added GridAperture and SiemensStar (the latter was available before but was not exposed to xrtQook) to xrtQook and to the docs, see [here](https://xrt.readthedocs.io/raycing.html#xrt.backends.raycing.apertures.GridAperture). You...

Hi, Since you don't set surface limits, although you asked about it in #104, rays may find an imaginary second reflection point at the back continuation of the reflected ray...

Hi! In your `run_process()` you can set the `geom` field of your crystal to one option and propagate the incoming beam through the crystal. Then change `geom` to another value...

... and I am not sure how this will work in multiprocessing. So first start with one process.

Hi! Your question is probably about the mosaic case. Please see [here](https://xrt.readthedocs.io/raycing.html#xrt.backends.raycing.materials.Crystal.__init__), in the *mosaicity* entry. Otherwise, look a bit lower for reflectivity and transmissivity formulas for perfect crystals. Not...

Certainly, you may redefine everything. The modules xrt/backends/raycing/oes_base.py and xrt/backends/raycing/materials.py can be considered as examples. I doubt one can call them "simple".

Hi, Simply don't use `get_epsilon_h()`. I put it there to test the Shvydko's Eq(2.119). It does the same calculations as `get_Darwin_width()` apart from being squared and having |F_h|² instead of...