Also undo the dithering in the other gravity scheme's io

src/gravity/Default/gravity_io.h

@@ -24,10 +24,11 @@
 INLINE static void convert_gpart_pos(const struct engine* e,
                                      const struct gpart* gp, double* ret) {
 
-  if (e->s->periodic) {
-    ret[0] = box_wrap(gp->x[0], 0.0, e->s->dim[0]);
-    ret[1] = box_wrap(gp->x[1], 0.0, e->s->dim[1]);
-    ret[2] = box_wrap(gp->x[2], 0.0, e->s->dim[2]);
+  const struct space* s = e->s;
+  if (s->periodic) {
+    ret[0] = box_wrap(gp->x[0] - s->pos_dithering[0], 0.0, s->dim[0]);
+    ret[1] = box_wrap(gp->x[1] - s->pos_dithering[1], 0.0, s->dim[1]);
+    ret[2] = box_wrap(gp->x[2] - s->pos_dithering[2], 0.0, s->dim[2]);
   } else {
     ret[0] = gp->x[0];
     ret[1] = gp->x[1];

src/gravity/Potential/gravity_io.h

@@ -23,11 +23,11 @@
 
 INLINE static void convert_gpart_pos(const struct engine* e,
                                      const struct gpart* gp, double* ret) {
-
-  if (e->s->periodic) {
-    ret[0] = box_wrap(gp->x[0], 0.0, e->s->dim[0]);
-    ret[1] = box_wrap(gp->x[1], 0.0, e->s->dim[1]);
-    ret[2] = box_wrap(gp->x[2], 0.0, e->s->dim[2]);
+  const struct space* s = e->s;
+  if (s->periodic) {
+    ret[0] = box_wrap(gp->x[0] - s->pos_dithering[0], 0.0, s->dim[0]);
+    ret[1] = box_wrap(gp->x[1] - s->pos_dithering[1], 0.0, s->dim[1]);
+    ret[2] = box_wrap(gp->x[2] - s->pos_dithering[2], 0.0, s->dim[2]);
   } else {
     ret[0] = gp->x[0];
     ret[1] = gp->x[1];