New slicing backend (nearest neighbors interpolation) for use with moving mesh

docs/source/visualisation/slice.rst

@@ -5,7 +5,7 @@ The :mod:`swiftsimio.visualisation.slice` sub-module provides an interface
 to render SWIFT data onto a slice. This takes your 3D data and finds the 3D
 density at fixed z-position, slicing through the box.
 
-This effectively solves the equation:
+The default :code:`"sph"` backend effectively solves the equation:
 
 :math:`\tilde{A}_i = \sum_j A_j W_{ij, 3D}`
 
@@ -14,6 +14,10 @@ with :math:`\tilde{A}_i` the smoothed quantity in pixel :math:`i`, and
 Here we use the Wendland-C2 kernel. Note that here we take the kernel
 at a fixed z-position.
 
+There is also an alternative :code:`"nearest_neighbours"` backend, which uses
+nearest-neighbour interpolation to compute the densities at each pixel.
+This backend is more suited for use with moving-mesh hydrodynamics schemes.
+
 The primary function here is
 :meth:`swiftsimio.visualisation.slice.slice_gas`, which allows you to
 create a gas slice of any field. See the example below.

pyproject.toml

@@ -3,7 +3,7 @@ requires = ["setuptools>=61.0"]
 build-backend = "setuptools.build_meta"
 
 [tool.setuptools]
-packages = ["swiftsimio", "swiftsimio.initial_conditions", "swiftsimio.metadata", "swiftsimio.metadata.cosmology", "swiftsimio.metadata.metadata", "swiftsimio.metadata.particle", "swiftsimio.metadata.unit", "swiftsimio.metadata.writer", "swiftsimio.visualisation", "swiftsimio.visualisation.projection_backends", "swiftsimio.visualisation.tools"]
+packages = ["swiftsimio", "swiftsimio.initial_conditions", "swiftsimio.metadata", "swiftsimio.metadata.cosmology", "swiftsimio.metadata.metadata", "swiftsimio.metadata.particle", "swiftsimio.metadata.unit", "swiftsimio.metadata.writer", "swiftsimio.visualisation", "swiftsimio.visualisation.projection_backends", "swiftsimio.visualisation.slice_backends", "swiftsimio.visualisation.tools"]
 
 [project]
 name = "swiftsimio"

swiftsimio/objects.py

@@ -41,6 +41,7 @@
     expm1,
     log1p,
     sqrt,
+    # cbrt,  # TODO: Needs upstream (unyt) support first
     square,
     reciprocal,
     sin,
@@ -220,6 +221,10 @@ def _square_cosmo_factor(ca_cf, **kwargs):
     return _power_cosmo_factor(ca_cf, (False, None), power=2)
 
 
+def _cbrt_cosmo_factor(ca_cf, **kwargs):
+    return _power_cosmo_factor(ca_cf, (False, None), power=1.0 / 3.0)
+
+
 def _divide_cosmo_factor(ca_cf1, ca_cf2, **kwargs):
     ca1, cf1 = ca_cf1
     ca2, cf2 = ca_cf2
@@ -640,6 +645,7 @@ class cosmo_array(unyt_array):
         log1p: _return_without_cosmo_factor,
         sqrt: _sqrt_cosmo_factor,
         square: _square_cosmo_factor,
+        # cbrt: _cbrt_cosmo_factor,  # TODO: Needs upstream (unyt) support first
         reciprocal: _reciprocal_cosmo_factor,
         sin: _return_without_cosmo_factor,
         cos: _return_without_cosmo_factor,

swiftsimio/visualisation/__init__.py

@@ -5,4 +5,4 @@
 from .projection import scatter, project_gas, project_gas_pixel_grid
 from .slice import slice_scatter as slice
 from .slice import slice_gas, slice_gas_pixel_grid
-from .smoothing_length_generation import generate_smoothing_lengths
+from .smoothing_length import generate_smoothing_lengths