diff --git a/distrib/distrib.cc b/distrib/distrib.cc
index 5d9a8e9..c16571c 100644
--- a/distrib/distrib.cc
+++ b/distrib/distrib.cc
@@ -304,17 +304,18 @@ int distrib::send_data(int task, unsigned char * data, int num_bytes)
 
 int distrib::getTask()
 {
+    int task = -1;
     if (m_server)
     {
         pthread_mutex_lock(&m_task_mutex);
-        int task = -1;
         if (m_next_task < m_num_tasks)
         {
             task = m_next_task;
             m_next_task++;
         }
         pthread_mutex_unlock(&m_task_mutex);
-        return task;
+        if (task > -1)
+            recordTask(task);
     }
     else
     {
@@ -323,9 +324,22 @@ int distrib::getTask()
             return -1;
 
         /* wait for a message back */
-        int task = 0;
         if (read(m_client_socket, &task, sizeof(task)) < 0)
             return -1;
-        return task;
     }
+    return task;
+}
+
+void distrib::recordTask(int task)
+{
+    pthread_mutex_lock(&m_tasks_in_progress_mutex);
+    m_tasks_in_progress[task] = 1;
+    pthread_mutex_unlock(&m_tasks_in_progress_mutex);
+}
+
+void distrib::taskDone(int task)
+{
+    pthread_mutex_lock(&m_tasks_in_progress_mutex);
+    m_tasks_in_progress.erase(task);
+    pthread_mutex_unlock(&m_tasks_in_progress_mutex);
 }
diff --git a/distrib/distrib.h b/distrib/distrib.h
index dfa4820..eabf9c9 100644
--- a/distrib/distrib.h
+++ b/distrib/distrib.h
@@ -4,6 +4,7 @@
 
 #include <string>
 #include <vector>
+#include <map>
 #include <pthread.h>
 
 #define UNIT_TASK_SIZE 50
@@ -25,6 +26,7 @@ class distrib
         void set_num_tasks(int num_tasks) { m_num_tasks = num_tasks; }
         int getTask();
         int send_data(int task, unsigned char * data, int num_bytes);
+        int getNumTasksInProgress() { return m_tasks_in_progress.size(); }
 
         typedef struct
         {
@@ -38,6 +40,8 @@ class distrib
     protected:
         int clientConnect(const std::string & host,
                           const std::vector<std::string> & client_options);
+        void recordTask(int task);
+        void taskDone(int task);
 
         std::vector<std::string> m_hosts;
         std::vector<int> m_children;
@@ -54,6 +58,8 @@ class distrib
         int m_next_task;
         bool m_server;
         pthread_mutex_t m_task_mutex;
+        std::map<int, int> m_tasks_in_progress;
+        pthread_mutex_t m_tasks_in_progress_mutex;
 };
 
 #endif
diff --git a/main/Scene.cc b/main/Scene.cc
index b19cdf6..6f7b270 100644
--- a/main/Scene.cc
+++ b/main/Scene.cc
@@ -160,7 +160,13 @@ void Scene::render()
         {
             /* work on tasks in this thread until there are no more */
             taskLoop();
-            /* TODO: wait until all data has arrived */
+            /* TODO: change wait condition */
+            for (;;)
+            {
+                if (m_distrib.getNumTasksInProgress() == 0)
+                    break;
+                usleep(100000);
+            }
         }
 
         if (m_verbose)