diff --git a/ag.cc b/ag.cc
index 2728ed2..3f6f7b0 100644
--- a/ag.cc
+++ b/ag.cc
@@ -24,10 +24,6 @@ namespace ag
             { "println", println },
             { "loadModel", loadModel },
             { "loadStaticModel", loadStaticModel },
-#if 0
-            { "videoStart", videoStart },
-            { "videoStop", videoStop },
-#endif
             { "sleep", sleep },
             { "startFrame", startFrame },
             { "endFrame", endFrame },
@@ -163,20 +159,6 @@ namespace ag
         loadModelSpecify(L, true);
     }
 
-#if 0
-    int videoStart(lua_State * L)
-    {
-        g_engine->getVideo()->start();
-        return 0;
-    }
-
-    int videoStop(lua_State * L)
-    {
-        g_engine->getVideo()->stop();
-        return 0;
-    }
-#endif
-
     int sleep(lua_State * L)
     {
         int argc = lua_gettop(L);
@@ -218,6 +200,12 @@ namespace ag
         return 1;
     }
 
+    int doPhysics(lua_State * L)
+    {
+        g_engine->doPhysics();
+        return 0;
+    }
+
     namespace object
     {
         static Engine::Object * getObject(lua_State * L, int index)
diff --git a/ag.h b/ag.h
index a3b9de7..a779a2a 100644
--- a/ag.h
+++ b/ag.h
@@ -11,13 +11,12 @@ namespace ag
     int println(lua_State * L);
     int loadModel(lua_State * L);
     int loadStaticModel(lua_State * L);
-    int videoStart(lua_State * L);
-    int videoStop(lua_State * L);
     int sleep(lua_State * L);
     int startFrame(lua_State * L);
     int endFrame(lua_State * L);
     int setCamera(lua_State * L);
     int elapsedTime(lua_State * L);
+    int doPhysics(lua_State * L);
 
     namespace object
     {
diff --git a/anaglym.cc b/anaglym.cc
index 6a7aeac..4da1353 100644
--- a/anaglym.cc
+++ b/anaglym.cc
@@ -267,7 +267,7 @@ Uint32 Engine::updateCallback(Uint32 interval)
 void Engine::run()
 {
     /* register a screen redrawing SDL event */
-    SDL_AddTimer(20, &updateCallback, this);
+    SDL_AddTimer(25, &updateCallback, this);
 
     SDL_Event event;
     while (SDL_WaitEvent(&event))
@@ -333,3 +333,16 @@ void Engine::Object::getPosition(double * x, double * y, double * z)
         *z = pos[2];
     }
 }
+
+void Engine::doPhysics()
+{
+    static Uint32 last_updated = 0;
+    Uint32 current_ticks = SDL_GetTicks();
+    if (last_updated > 0)
+    {
+        Uint32 msec_steps = current_ticks - last_updated;
+        for (int i = 0; i < msec_steps; i++)
+            m_world.step();
+    }
+    last_updated = current_ticks;
+}
diff --git a/anaglym.h b/anaglym.h
index fcd5ed3..7809c5e 100644
--- a/anaglym.h
+++ b/anaglym.h
@@ -41,6 +41,7 @@ class Engine
         OdeWorld & getWorld() { return m_world; }
         int addObject(WFObj * obj);
         Object * getObject(int id);
+        void doPhysics();
 
         /* lua services */
         int startFrame(lua_State * L);