Call the gpart functions rather than reading directly their fields in the...

Call the gpart functions rather than reading directly their fields in the velociraptor interface. Temporary workaround for stars.

src/velociraptor_interface.c

@@ -207,11 +207,11 @@ void velociraptor_invoke(struct engine *e) {
       swift_parts[i].x[0] = gparts[i].x[0];
       swift_parts[i].x[1] = gparts[i].x[1];
       swift_parts[i].x[2] = gparts[i].x[2];
-      swift_parts[i].v[0] = gparts[i].v_full[0] / a2;
+      swift_parts[i].v[0] = gparts[i].v_full[0] / a2; //MATTHIEU: Check this a^2 !!
       swift_parts[i].v[1] = gparts[i].v_full[1] / a2;
       swift_parts[i].v[2] = gparts[i].v_full[2] / a2;
-      swift_parts[i].mass = gparts[i].mass;
-      swift_parts[i].potential = gparts[i].potential;
+      swift_parts[i].mass = gravity_get_mass(&gparts[i]);
+      swift_parts[i].potential = gravity_get_comoving_potential(&gparts[i]); //MATTHIEU: Need factors here?
       swift_parts[i].type = gparts[i].type;
       
       /* Set gas particle IDs from their hydro counterparts and set internal energies. */
@@ -219,11 +219,13 @@ void velociraptor_invoke(struct engine *e) {
         swift_parts[i].id = parts[-gparts[i].id_or_neg_offset].id;
         swift_parts[i].u = hydro_get_physical_internal_energy(&parts[-gparts[i].id_or_neg_offset], e->cosmology) * energy_scale;
       }
-      else {
+      else if (gparts[i].type == swift_type_dark_matter) {
         swift_parts[i].id = gparts[i].id_or_neg_offset;
         swift_parts[i].u = 0.f;
       }
-
+      else {
+	error("Particle type not handled by velociraptor (yet?) !");
+      }
     }
 
     /* Call VELOCIraptor. */