diff --git a/ag.cc b/ag.cc
index ecd0e38..6b1924d 100644
--- a/ag.cc
+++ b/ag.cc
@@ -31,6 +31,7 @@ namespace ag
             { "elapsedTime", elapsedTime },
             { "doPhysics", doPhysics },
             { "drawObjects", drawObjects },
+            { "setAutoPhysics", setAutoPhysics },
             { NULL, NULL }
         };
         luaL_register(L, "ag", functions);
@@ -225,6 +226,21 @@ namespace ag
         return 0;
     }
 
+    int setAutoPhysics(lua_State * L)
+    {
+        int argc = lua_gettop(L);
+
+        if (argc == 1)
+        {
+            if (lua_isboolean(L, 1))
+            {
+                g_engine->setAutoPhysics(lua_toboolean(L, 1));
+            }
+        }
+
+        return 0;
+    }
+
     namespace object
     {
         static Engine::Object * getObject(lua_State * L, int index)
diff --git a/ag.h b/ag.h
index add00f4..df4abe1 100644
--- a/ag.h
+++ b/ag.h
@@ -18,6 +18,7 @@ namespace ag
     int elapsedTime(lua_State * L);
     int doPhysics(lua_State * L);
     int drawObjects(lua_State * L);
+    int setAutoPhysics(lua_State * L);
 
     namespace object
     {
diff --git a/anaglym.cc b/anaglym.cc
index 18fc24c..4006e62 100644
--- a/anaglym.cc
+++ b/anaglym.cc
@@ -90,6 +90,7 @@ Engine::Engine()
     m_up[1] = 0;
     m_up[2] = 1;
     m_drawing = false;
+    m_autoPhysics = true;
 
     /* setup redraw SDL event structure */
     userEvent.type = SDL_USEREVENT;
@@ -334,6 +335,8 @@ RET:
 void Engine::update()
 {
     m_drawing = true;
+    if (m_autoPhysics)
+        doPhysics();
     lua_getfield(m_luaState, LUA_GLOBALSINDEX, "update");
     if (lua_type(m_luaState, -1) == LUA_TFUNCTION)
     {
diff --git a/anaglym.h b/anaglym.h
index ceb821c..8926254 100644
--- a/anaglym.h
+++ b/anaglym.h
@@ -60,6 +60,8 @@ class Engine
         Object * getObject(int id);
         void doPhysics();
         void drawObjects();
+        void setAutoPhysics(bool autoPhysics) { m_autoPhysics = autoPhysics; }
+        bool getAutoPhysics() { return m_autoPhysics; }
 
         /* lua services */
         int startFrame(lua_State * L);
@@ -89,6 +91,7 @@ class Engine
         GLdouble    m_center[3];
         GLdouble    m_up[3];
         bool        m_drawing;
+        bool        m_autoPhysics;
 };
 
 extern Engine * g_engine;
diff --git a/tests/ballstairs.lua b/tests/ballstairs.lua
index 1be70f3..56bf7ca 100755
--- a/tests/ballstairs.lua
+++ b/tests/ballstairs.lua
@@ -2,7 +2,6 @@
 function update()
     ballx, bally, ballz = ball:getPosition()
     ag.setCamera(7, -6, 15, ballx, bally, ballz, 0, 0, 1)
-    ag.doPhysics()
     ag.startFrame()
     ag.drawObjects()
     ag.endFrame()