Most of the transforms kind of work now need to hook in the new timer.

animate2.cpp

@@ -78,6 +78,7 @@ namespace animate2 {
 
   void Timer::start() {
     clock.start();
+    prev_time = clock.getElapsedTime().asSeconds();
   }
 
   void Timer::reset() {
@@ -86,25 +87,34 @@ namespace animate2 {
 
   void Timer::restart() {
     clock.restart();
+    prev_time = clock.getElapsedTime().asSeconds();
   }
 
   sf::Time Timer::getElapsedTime() {
     return clock.getElapsedTime();
   }
 
-  void Timer::begin() {
-    prev_time = clock.getElapsedTime().asSeconds();
-  }
-
   std::pair<int, double> Timer::commit() {
+    // determine frame duration based on previous time
     current_time = clock.getElapsedTime().asSeconds();
     frame_duration = current_time - prev_time;
+
+    // update prev_time for the next call
+    prev_time = current_time;
+
+    // update accumulator, retaining previous errors
     accumulator += frame_duration;
 
+    // find the tick count based on DELTA
     double tick_count = accumulator / DELTA;
+    // alpha is then the remainder/fractional part
     double alpha = modf(tick_count, &tick_count);
-    accumulator -= tick_count * DELTA;
 
+    // reduce accumulator by the number of DELTAS
+    accumulator -= tick_count * DELTA;
+    // that leaves the remaining errors for next loop
+
+    // return the number of even DELTA ticks and the alpha
     return {int(tick_count), alpha};
   }