Get the correct conversion factors for volumes.

src/hydro/Gizmo/hydro_io.h

@@ -124,8 +124,8 @@ void hydro_write_particles(struct part* parts, struct io_props* list,
                                  UNIT_CONV_ACCELERATION, parts, a_hydro);
   list[7] = io_make_output_field("Density", FLOAT, 1, UNIT_CONV_DENSITY, parts,
                                  primitives.rho);
-  list[8] = io_make_output_field("Volume", FLOAT, 1, UNIT_CONV_VOLUME, parts,
-                                 geometry.volume);
+  list[8] = io_make_output_field("Volume", FLOAT, 1, UNIT_CONV_INV_VOLUME,
+                                 parts, geometry.volume);
   list[9] = io_make_output_field("GradDensity", FLOAT, 3, UNIT_CONV_DENSITY,
                                  parts, primitives.gradients.rho);
   list[10] = io_make_output_field_convert_part(

src/units.c

@@ -319,6 +319,9 @@ void units_get_base_unit_exponants_array(float baseUnitsExp[5],
       break;
 
     case UNIT_CONV_VOLUME:
+      baseUnitsExp[UNIT_LENGTH] = 3.f;
+
+    case UNIT_CONV_INV_VOLUME:
       baseUnitsExp[UNIT_LENGTH] = -3.f;
   }
 }

src/units.h

@@ -90,7 +90,8 @@ enum UnitConversionFactor {
   UNIT_CONV_MAGNETIC_FIELD,
   UNIT_CONV_MAGNETIC_INDUCTANCE,
   UNIT_CONV_TEMPERATURE,
-  UNIT_CONV_VOLUME
+  UNIT_CONV_VOLUME,
+  UNIT_CONV_INV_VOLUME
 };
 
 void units_init_cgs(struct UnitSystem*);