rulegen3:: faster get_parent_dir

rulegen.cpp

@@ -941,6 +941,16 @@ EX twalker get_parent_dir(twalker& cw) {
   
   be_solid(c);
 
+  if(WDIM == 3) {
+    for(int i=0; i<c->type; i++) {
+      tcell *c1 = c->cmove(i);
+      if(c1->dist < c->dist) {
+        c->parent_dir = i;
+        return twalker(c, i);
+        }
+      }
+    }
+
   auto oc = c;
 
   if(c->dist > 0) {