Animator now can apply transforms using the timer alpha which mostly works.

animate2.cpp

@@ -71,9 +71,8 @@ namespace animate2 {
     update_frame();
   }
 
-  void Animate2::motion(sf::Vector2f& pos, sf::Vector2f& scale) {
-    $transform.twitching($sequence);
-    $transform.lerp($sequence, pos, scale);
+  void Animate2::motion(sf::Vector2f& pos, sf::Vector2f& scale, float alpha) {
+    $transform.lerp($sequence, pos, scale, alpha);
   }
 
   void Timer::start() {
@@ -106,25 +105,25 @@ namespace animate2 {
     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);
+    double tick_count = floor(accumulator / DELTA);
 
     // reduce accumulator by the number of DELTAS
     accumulator -= tick_count * DELTA;
     // that leaves the remaining errors for next loop
 
+    // alpha is then what we lerp...but WHY?!
+    alpha = accumulator / DELTA;
+
     // return the number of even DELTA ticks and the alpha
     return {int(tick_count), alpha};
   }
 
-  float Transform::twitching(Sequence& seq) {
-    float tick = 1 - std::powf(ease_rate, seq.subframe + 0.0001);
-    return easing(tick);
+  float Transform::twitching(Sequence& seq, float alpha) {
+    return easing(alpha);
   }
 
-  void Transform::lerp(Sequence& seq, sf::Vector2f& pos_out, sf::Vector2f& scale_out) {
-    float tick = std::abs(twitching(seq));
+  void Transform::lerp(Sequence& seq, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float alpha) {
+    float tick = std::abs(twitching(seq, alpha));
     return motion(*this, pos_out, scale_out, tick);
   }
 }

animate2.hpp

@@ -64,8 +64,8 @@ namespace animate2 {
     ease2::EaseFunc easing = ease2::in_out_back;
     ease2::MoveFunc motion = ease2::move_rush;
 
-    float twitching(Sequence& seq);
-    void lerp(Sequence& seq, sf::Vector2f& pos_out, sf::Vector2f& scale_out);
+    float twitching(Sequence& seq, float alph);
+    void lerp(Sequence& seq, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float alpha);
   };
 
   /* Gets the number of times it looped, and returns if it should stop. */
@@ -94,7 +94,7 @@ namespace animate2 {
       void apply(sf::Sprite& sprite);
       void update_frame();
       void update();
-      void motion(sf::Vector2f& pos_out, sf::Vector2f& scale_out);
+      void motion(sf::Vector2f& pos_out, sf::Vector2f& scale_out, float alpha);
   };
 
 }

tests/animate2.cpp

@@ -180,7 +180,7 @@ TEST_CASE("confirm transition changes work", "[animation-new]") {
     start = clock.getElapsedTime();
 
     anim.update();
-    anim.motion(pos, scale);
+    anim.motion(pos, scale, 0.8f);
     std::this_thread::sleep_for(10ms);
     fmt::println("POSITION: {},{}; SCALE: {},{}; current: {}; subframe: {}",
         pos.x, pos.y, scale.x, scale.y, anim.$sequence.current, anim.$sequence.subframe);

tools/animator.cpp

@@ -161,10 +161,10 @@ animate2::Sequence sequence{
 };
 
 animate2::Transform transform{
-  .min_x{-40.0f},
-    .min_y{-40.0f},
-    .max_x{40.0f},
-    .max_y{40.0f},
+  .min_x{-20.0f},
+    .min_y{-20.0f},
+    .max_x{20.0f},
+    .max_y{20.0f},
     .simple{false},
     .flipped{false},
     .ease_rate{0.5f},
@@ -173,7 +173,7 @@ animate2::Transform transform{
     .stationary{true},
     .toggled{false},
     .looped{true},
-    .easing = ease2::out_circle,
+    .easing = ease2::out_bounce,
     .motion = ease2::move_bounce,
 };
 
@@ -204,16 +204,6 @@ int main(int argc, char* argv[]) {
   sf::Vector2f scale = sprite->getScale();
 
   while(main.active()) {
-    anim.apply(*sprite);
-
-    sf::Vector2f new_pos = pos;
-    sf::Vector2f new_scale = scale;
-    anim.motion(new_pos, new_scale);
-    sprite->setPosition(new_pos);
-    sprite->setScale(new_scale);
-
-    main.render();
-
     auto [ticks, alpha] = timer.commit();
     fmt::println("TICK: {}, alpha: {}", ticks, alpha);
 
@@ -222,8 +212,17 @@ int main(int argc, char* argv[]) {
       anim.update();
     }
 
-    // do something with alpha....
+    anim.apply(*sprite);
 
+    sf::Vector2f new_pos = pos;
+    sf::Vector2f new_scale = scale;
+    anim.motion(new_pos, new_scale, alpha);
+    sprite->setPosition(new_pos);
+    sprite->setScale(new_scale);
+
+    main.render();
+
+    // do something with alpha....
     main.handle_keyboard_mouse();
   }