diff --git a/hyper.h b/hyper.h
index 15d64bb9..bc11d600 100644
--- a/hyper.h
+++ b/hyper.h
@@ -4317,5 +4317,9 @@ extern int cells_drawn;
 void menuitem_sightrange(char c = 'r');
 
 bool in_smart_range(const transmatrix& T);
+
+void curvepoint(const hyperpoint& H1);
+dqi_poly& queuecurve(color_t linecol, color_t fillcol, PPR prio);
+
 }
 
diff --git a/rogueviz-fundamental.cpp b/rogueviz-fundamental.cpp
new file mode 100644
index 00000000..9d33292c
--- /dev/null
+++ b/rogueviz-fundamental.cpp
@@ -0,0 +1,229 @@
+// show the fundamental domain for quotient spaces
+// Copyright (C) 2018 Zeno and Tehora Rogue, see 'hyper.cpp' for details
+
+namespace hr {
+
+namespace fundamental {
+
+color_t color1, color2;
+
+map<cell*, int> same;
+map<cell*, transmatrix> gm;
+
+bool is_connected(cellwalker cw) {
+  return same[cw.at] & (1<<cw.spin);
+  }
+
+void be_connected(cellwalker cw) {
+  // transmatrix T = gm[cw.at];
+  same[cw.at] |= (1<<cw.spin);
+  cw += wstep;
+  same[cw.at] |= (1<<cw.spin);
+  /* printf("%s", display(T * C0)); 
+  printf(" %s\n", display(gm[cw.at] * C0)); */
+  // queueline(T * C0, gm[cw.at] * C0, 0xFF0000FF, 3);
+  }
+
+int funmode = 0;
+
+hyperpoint corner(cellwalker cw) {
+  transmatrix T = gm[cw.at];
+  if(funmode == 2) {
+    while(cw.at->type != S7) { 
+      cw++; 
+      T = T * calc_relative_matrix(cw.peek(), cw.at, cw.spin);
+      cw += wstep; 
+      }
+    return T * C0;
+    }
+  return gm[cw.at] * get_corner_position(cw.at, cw.spin+(cw.mirrored?0:1), 3);
+  }
+
+transmatrix rel(cellwalker cw) {
+  return calc_relative_matrix(cw.cpeek(), cw.at, cw.spin);
+  }
+
+transmatrix labelpos(hyperpoint h1, hyperpoint h2) {
+  hyperpoint h = mid(h1, h2);
+  transmatrix T = rgpushxto0(h);
+  hyperpoint hx = inverse(T) * h2;
+  ld alpha = atan2(-hx[1], hx[0]);
+  return T * xspinpush(alpha + M_PI/2, .3);
+  }
+ 
+void fundamental_marker() {
+  if(!funmode || !quotient) return;
+  same.clear();
+  gm.clear();
+  
+  same[cwt.at] = 0;
+  gm[cwt.at] = ggmatrix(cwt.at);
+  
+  vector<cell*> cells;
+  cells.push_back(cwt.at);
+  
+  int tree_edges = 0;
+  int face_edges = 0;
+  
+  for(int k=0; k<isize(cells); k++) {
+    cell *c = cells[k];
+    for(int i=0; i<c->type; i++) {
+      cellwalker cw(c, i);
+      cell *c2 = cw.cpeek();
+      if(gm.count(c2)) continue;
+      gm[c2] = gm[c] * rel(cw);
+      // queueline(gm[c2] * C0, gm[c2] * xspinpush0(ticks, 0.2), 0xFFFFFFFF, 3);
+      be_connected(cw);
+      tree_edges++;
+      cells.push_back(c2);
+      }
+    }
+  
+  while(true) {
+    int f = face_edges;
+    for(int k=0; k<isize(cells); k++) {
+      cell *c = cells[k];
+      for(int i=0; i<c->type; i++) {
+        cellwalker cw(c, i);
+        if(is_connected(cw) && is_connected(cw+1) && !is_connected(cw+wstep-1)) {
+          face_edges++;
+          be_connected(cw+wstep-1);
+          }
+        }
+      }
+    if(f == face_edges) break;
+    }
+  
+  cellwalker cw;
+  
+  int corners = 0;
+
+  for(int k=0; k<isize(cells); k++) {
+    cell *c = cells[k];
+    for(int i=0; i<c->type; i++) {
+      cellwalker cw0(c, i);
+      if(!is_connected(cw0) && !is_connected(cw0+1) && !is_connected(cw0+wstep-1))
+        corners++, cw = cw0;
+      }
+    }
+  
+  // printf("tree edges = %d, face edges = %d, corners = %d\n", tree_edges, face_edges, corners);
+  
+  map<cellwalker, cellwalker> next_corner;
+  map<cellwalker, cellwalker> prev_corner;
+  
+  for(int ci=0; ci<corners; ci++) {
+    cellwalker cw0 = cw;
+        
+    while(true) {
+      cw++;
+      if(is_connected(cw)) {
+        cw += wstep;
+        cw++;
+        }
+      if(!is_connected(cw+1) && !is_connected(cw+wstep-1))
+        break;
+      }
+    
+    next_corner[cw0] = cw;
+    prev_corner[cw] = cw0;
+    }
+
+  vector<transmatrix> nearm;
+
+  for(int ci=0; ci<corners; ci++) {
+    for(int u=0; u<1; u++) {
+      cellwalker cw1 = cw+u+wstep+(u-1);
+      /* printf("%p/%d %p/%d ", cw.at, cw.spin, cw1.at, cw1.spin);
+      printf("[%d %d %d] ", is_connected(cw), is_connected(cw+1), is_connected(cw+wstep-1));
+      printf("[%d %d %d] ", is_connected(cw1), is_connected(cw1+1), is_connected(cw1+wstep-1));
+      printf("%d %d;\n", !!next_corner.count(cw1), !!next_corner.count(cw1+wmirror-1)); */
+      transmatrix T_here = gm[cw.at] * rel(cw+u);
+      transmatrix T_there = gm[cw1.at];
+      nearm.push_back(T_here * inverse(T_there));
+      }
+    cw = next_corner[cw];
+    }
+  
+  vid.linewidth *= 5;
+
+  for(int ci=0; ci<corners; ci++) {
+
+    hyperpoint h = corner(cw);
+    cw = next_corner[cw];
+    hyperpoint h2 = corner(cw);
+    
+    for(auto& T: nearm) queueline(T * h, T * h2, color1, 3);
+    }
+    
+  for(int ci=0; ci<corners; ci++) {
+
+    hyperpoint h = corner(cw);
+    cw = next_corner[cw];
+    hyperpoint h2 = corner(cw);
+    
+    queueline(h, h2, color2, 3);
+    }
+  
+  if(0) for(int k=0; k<isize(cells); k++) {
+    cell *c = cells[k];
+    for(int i=0; i<c->type; i++) {
+      cellwalker cw0(c, i);
+      if(!is_connected(cw0)) continue;
+      int v = 0;
+      for(auto& n: nearm) {
+        queueline(n * gm[cw0.at] * xspinpush0(v, .05), n * gm[cw0.cpeek()] * xspinpush0(v, .05), 0xFF8000FF, 0);
+        v++;
+        }
+      queueline(gm[cw0.at] * C0, gm[cw0.cpeek()] * C0, 0xFF0000FF, 0);
+      }
+    }
+
+  set<cellwalker> visited;
+  
+  int id = 0;
+  
+  for(int ci=0; ci<corners; ci++) {
+    
+    cellwalker cw1 = (cw+1+wstep);
+    bool mirrored = false;
+    if(!next_corner.count(cw1)) cw1 = cw1 + wmirror - 1, mirrored = true;
+
+    // visited.insert(next_corner[cw]);
+    // cellwalker cw2 = next_corner[cw];
+    if(next_corner[cw] < (mirrored ? next_corner[cw1] : cw1)) {
+    
+      int mc = (mirrored ? color1 : color2) >> 8;
+      if(hdist(corner(cw), corner(next_corner[cw])) > 1e-3) {
+        queuestr(labelpos(corner(cw), corner(next_corner[cw])), 1/scalefactor, its(id), mc);
+        if(mirrored)
+          queuestr(labelpos(corner(cw1), corner(next_corner[cw1])), 1/scalefactor, its(id), mc);
+        else
+          queuestr(labelpos(corner(prev_corner[cw1]), corner(cw1)), 1/scalefactor, its(id), mc);
+        id++;
+        }      
+      }
+    cw = next_corner[cw];
+    }
+
+  vid.linewidth /= 5;
+  }
+
+int readArgs() {
+  using namespace arg;
+           
+  if(0) ;
+  else if(argis("-fundamental")) {
+    shift(); funmode = argi();
+    shift(); color1 = arghex();
+    shift(); color2 = arghex();
+    }
+  else return 1;
+  return 0;
+  }
+
+auto fundamentalhook = addHook(hooks_args, 100, readArgs) + addHook(hooks_frame, 100, fundamental_marker);
+
+}
+
+}
\ No newline at end of file
diff --git a/rogueviz.cpp b/rogueviz.cpp
index 3a4298d4..a97a4199 100644
--- a/rogueviz.cpp
+++ b/rogueviz.cpp
@@ -2277,3 +2277,4 @@ auto hooks  =
 #include "rogueviz-video.cpp"
 #include "rogueviz-pentagonal.cpp"
 #include "rogueviz-graph.cpp"
+#include "rogueviz-fundamental.cpp"