Add illustration of inhomogeneity from absorption

docs/user-guide/dream/dream-instrument-view.ipynb

@@ -229,6 +229,65 @@
    "source": [
     "dream.instrument_view(dg[\"endcap_backward\"][\"module\", 0].hist(tof=1))"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "15",
+   "metadata": {},
+   "source": [
+    "## Display inhomogeneity from absorption\n",
+    "\n",
+    "If the sample absorbs or scatters a large fraction of the incoming neutrons the intensity in the detector will vary even if the scattering is inhomogeneous.\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "16",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import scipp as sc\n",
+    "\n",
+    "from scippneutron.absorption import compute_transmission_map\n",
+    "from scippneutron.absorption.cylinder import Cylinder\n",
+    "from scippneutron.absorption.material import Material\n",
+    "from scippneutron.atoms import ScatteringParams\n",
+    "\n",
+    "\n",
+    "material =  Material(\n",
+    "    scattering_params=ScatteringParams.for_isotope('V'),\n",
+    "    effective_sample_number_density=sc.scalar(0.07192, unit='1/angstrom**3')\n",
+    ")\n",
+    "sample_shape = Cylinder(\n",
+    "    symmetry_line=sc.vector([0, 1, 0]),\n",
+    "    center_of_base=sc.vector([0, -.5, 0], unit='cm'),\n",
+    "    radius=sc.scalar(1, unit='cm'),\n",
+    "    height=sc.scalar(5., unit='cm')\n",
+    ")\n",
+    "\n",
+    "transmission_fraction = compute_transmission_map(\n",
+    "    sample_shape,\n",
+    "    material,\n",
+    "    beam_direction=sc.vector([0, 0, 1]),\n",
+    "    wavelength=sc.linspace('wavelength', 4, 8, 20, unit='angstrom'),\n",
+    "    detector_position=dg['mantle'].coords['position']['strip', ::4]['wire', ::2].copy(),\n",
+    "    quadrature_kind='cheap',\n",
+    ")\n",
+    "\n",
+    "transmission_fraction.coords['position'] = transmission_fraction.coords.pop('detector_position')\n",
+    "dream.instrument_view(transmission_fraction.transpose((*set(transmission_fraction.dims) - {'wavelength'}, 'wavelength')), dim='wavelength')"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "17",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "transmission_fraction"
+   ]
   }
  ],
  "metadata": {