From a180da1dd5962055ef47332ef750b59aadb47a42 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Tcho=C5=84?= <dantch@onet.eu>
Date: Wed, 15 Apr 2026 17:41:00 +0200
Subject: [PATCH] Fix diffraction (#1)

* Simple but slow fix to allow observing diffraction mode again

* Tried to introduce some optimizations but couldn't, current version is good-enough
---
 .../simulation/crystal.py                     | 33 ++++++++++++-------
 .../simulation/stage.py                       |  2 +-
 2 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/src/instamatic-tem-emulator/simulation/crystal.py b/src/instamatic-tem-emulator/simulation/crystal.py
index 64f5c56..0fc052e 100644
--- a/src/instamatic-tem-emulator/simulation/crystal.py
+++ b/src/instamatic-tem-emulator/simulation/crystal.py
@@ -4,7 +4,6 @@
 
 import numpy as np
 from diffpy import structure as diffpy
-from diffsims.crystallography._diffracting_vector import DiffractingVector
 from diffsims.generators.simulation_generator import Simulation2D, SimulationGenerator
 from orix.crystal_map import Phase
 from orix.quaternion import Rotation
@@ -65,11 +64,6 @@ def __init__(
             lattice=self.lattice,
         )
         self.phase = Phase(space_group=space_group, structure=self.structure)
-        # self.recip = DiffractingVector.from_min_dspacing(
-        #     self.phase,
-        #     min_dspacing=1,
-        #     include_zero_vector=False,
-        # )  raises exception to use ReciprocalLatticeVector instead - version 0.7.0 issue?
         self.recip = Vector3D.from_min_dspacing(
             self.phase,
             min_dspacing=1,
@@ -161,7 +155,7 @@ def reciprocal_space_lattice(self, d_min: float) -> np.ndarray:
         vecs = self.lattice.reciprocal().cartesian(hkls)
         return vecs
 
-    def diffraction_pattern_mask(
+    def diffraction_pattern(
         self,
         shape: tuple[int, int],
         d_min: float,
@@ -201,10 +195,27 @@ def diffraction_pattern_mask(
         max_excitation_error = excitation_error
 
         rotation = Rotation.from_matrix(rotation_matrix)
-        from diffsims.generators.simulation_generator import (
-            Vector3d,
-            get_intersection_with_ewalds_sphere,
-        )
+        try:
+            from diffsims.generators.simulation_generator import (
+                Vector3d,
+                get_intersection_with_ewalds_sphere,
+            )
+        except ImportError:
+            sim = gen.calculate_diffraction2d(
+                phase=self.phase,
+                rotation=rotation,
+                reciprocal_radius=1 / d_min,
+                with_direct_beam=False,
+                max_excitation_error=max_excitation_error,
+            )
+            pattern = sim.get_diffraction_pattern(
+                shape=shape,
+                sigma=1,
+                calibration=1 / d_min / (shape[0] / 2),
+            )
+            return pattern * intensity_scale
+
+        # code below only works with https://github.com/pyxem/diffsims/pull/232
         optical_axis = rotation * Vector3d.zvector()
 
         # Calculate the reciprocal lattice vectors that intersect the Ewald sphere.
diff --git a/src/instamatic-tem-emulator/simulation/stage.py b/src/instamatic-tem-emulator/simulation/stage.py
index 9a9bd73..b8aa2eb 100644
--- a/src/instamatic-tem-emulator/simulation/stage.py
+++ b/src/instamatic-tem-emulator/simulation/stage.py
@@ -270,7 +270,7 @@ def get_diffraction_pattern(
                 # Crystal is completely on the grid
                 continue
 
-            reflections += self.crystals[sample.crystal_index].diffraction_pattern_mask(
+            reflections += self.crystals[sample.crystal_index].diffraction_pattern(
                 shape,
                 d_min=d_min,
                 rotation_matrix=self.rotation_matrix @ sample.rotation_matrix,