diff --git a/rogueviz/ads/display.cpp b/rogueviz/ads/display.cpp
index 14875d13..32d33fe6 100644
--- a/rogueviz/ads/display.cpp
+++ b/rogueviz/ads/display.cpp
@@ -135,11 +135,17 @@ void draw_game_cell(const cell_to_draw& cd) {
         rock.pts.push_back(f);
         });
       }
-    
+
     if(hv) {
-      ads_point M = current * (V * rock.at) * ads_matrix(Id, rock.pt_main.shift) * C0;
+      ld t = rock.life_start;
+      if(t < -100) t = 0;
+      ld shift = floor((rock.pt_main.shift - t) / spacetime_step) * spacetime_step + t;
+      ads_point M = current * (V * rock.at) * ads_matrix(Id, shift) * C0;
       optimize_shift(M);
-      for(ld z=-5; z<=5; z+=0.2) {
+      for(int z0=-spacetime_qty; z0<=spacetime_qty; z0++) {
+        ld z = z0 * spacetime_step;
+        if((shift+z) < rock.life_start) continue;
+        if((shift+z) > rock.life_end) continue;
         for(int i=0; i<isize(shape); i += 2) {
           auto h = rots::uxpush(shape[i] * ads_scale) * rots::uypush(shape[i+1] * ads_scale) * C0;
           curvepoint(h);
diff --git a/rogueviz/ads/ds-game.cpp b/rogueviz/ads/ds-game.cpp
index 18c67621..dc509828 100644
--- a/rogueviz/ads/ds-game.cpp
+++ b/rogueviz/ads/ds-game.cpp
@@ -501,10 +501,13 @@ void view_ds_game() {
 
       if(hv) {
         ld t = rock.at.shift;
-        if(rock.type == oMainRock) t = floor(10*t + .5) / 10;
+        if(rock.type == oMainRock) t = floor(t / spacetime_step + .5) * spacetime_step;
         transmatrix at = current.T * lorentz(2, 3, t - current.shift) * rock.at.T;
-        for(ld s=-3; s<=3; s+=0.1) {
-          transmatrix at1 = at * lorentz(2, 3, s);
+        for(int z0=-spacetime_qty; z0<=spacetime_qty; z0++) {
+          ld z = z0 * spacetime_step;
+          if(t-z < rock.life_start) continue;
+          if(t-z > rock.life_end) continue;
+          transmatrix at1 = at * lorentz(2, 3, z);
           if((at1 * pov) [2] < 0) continue;
 
           auto& sh = *rock.shape;
diff --git a/rogueviz/ads/globals.cpp b/rogueviz/ads/globals.cpp
index e015a03d..99aa833b 100644
--- a/rogueviz/ads/globals.cpp
+++ b/rogueviz/ads/globals.cpp
@@ -136,4 +136,6 @@ bool ads_draw_cell(cell *c, const shiftmatrix& V);
 extern transmatrix Duality;
 extern int use_duality;
 
+ld spacetime_step = 0.1;
+int spacetime_qty = 30;
 }}