Synced animations looks good.

src/AnimNodes/AnimSamplerNode.h

@@ -10,26 +10,47 @@
 struct AnimSamplerNode : public AnimNode {
   AnimSamplerNode(AnimationController* animation_controller)
       : AnimNode(animation_controller),
-        m_anim_ratio(0.f),
-        m_override_ratio(false){};
+        m_override_ratio(false),
+        m_anim_ratio(0.f) {
+    assert(m_current_time < 100.0f);
+    m_anim_node_type = AnimNodeType::AnimSampler;
+  };
   virtual ~AnimSamplerNode() {}
 
   ozz::animation::Animation* m_animation;
 
-  float m_anim_ratio;
   bool m_override_ratio;
+  float m_anim_ratio;
 
   ozz::animation::SamplingCache m_sampling_cache;
 
   void SetAnimation(ozz::animation::Animation* animation);
 
-  virtual void Update(float dt) override {
+  virtual void UpdateIsSynced(bool is_synced) override {
+    m_is_time_synced = is_synced;
+  }
+
+  virtual void EvalAnimDuration() override {
+    m_anim_duration = m_animation->duration();
+  }
+
+  virtual void UpdateTime(float dt) override {
     m_current_time += dt;
     if (!m_override_ratio) {
-      const float duration = m_animation->duration();
-      m_anim_ratio = fmodf((float)m_current_time / duration, 1.0f);
+      if (m_is_time_synced) {
+        m_anim_ratio = fmodf((float)m_current_time, 1.0f);
+        m_current_time = m_anim_ratio;
+      } else {
+        const float duration = m_animation->duration();
+        m_anim_ratio = fmodf((float)m_current_time / duration, 1.0f);
+      }
+    }
+
+    if (m_anim_ratio < 0.f) {
+      m_anim_ratio += 1.0f;
     }
   }
+
   virtual void Evaluate(
       ozz::vector<ozz::math::SoaTransform>* local_matrices) override;
 

src/AnimNodes/BlendNode.cc

@@ -13,7 +13,9 @@ BlendNode::BlendNode(AnimationController* animation_controller)
     : AnimNode(animation_controller),
       m_input_A(nullptr),
       m_input_B(nullptr),
-      m_weight(0.f) {
+      m_weight(0.f),
+      m_sync_inputs(false) {
+  m_anim_node_type = AnimNodeType::Blend;
   const SkinnedMesh* skinned_mesh = m_animation_controller->m_skinned_mesh;
   const int num_soa_joints = skinned_mesh->m_skeleton.num_soa_joints();
   const int num_joints = skinned_mesh->m_skeleton.num_joints();
@@ -54,6 +56,7 @@ void BlendNode::DrawDebugUi() {
     ImGui::Text("Input B:");
     m_input_B->DrawDebugUi();
     ImGui::SliderFloat("Weight", &m_weight, 0.f, 1.f);
+    ImGui::Checkbox("Sync Inputs", &m_sync_inputs);
     ImGui::TreePop();
   }
 }

src/AnimNodes/BlendNode.h

@@ -9,11 +9,13 @@
 
 struct BlendNode : public AnimNode {
   BlendNode(AnimationController* animation_controller);
+
   virtual ~BlendNode() {}
 
   AnimNode* m_input_A;
   AnimNode* m_input_B;
   float m_weight;
+  bool m_sync_inputs;
 
   ozz::vector<ozz::math::SoaTransform> m_local_matrices_A;
   ozz::vector<ozz::math::SoaTransform> m_local_matrices_B;
@@ -22,9 +24,37 @@ struct BlendNode : public AnimNode {
     m_current_time = 0.f;
   }
 
-  virtual void Update(float dt) {
-    m_input_A->Update(dt);
-    m_input_B->Update(dt);
+  virtual void UpdateIsSynced(bool is_synced) override {
+    m_is_time_synced = is_synced;
+
+    if (m_sync_inputs) {
+      m_is_time_synced = true;
+    }
+
+    m_input_B->UpdateIsSynced(m_is_time_synced);
+    m_input_A->UpdateIsSynced(m_is_time_synced);
+  }
+
+  virtual void EvalAnimDuration() override {
+    if (m_is_time_synced) {
+      m_anim_duration = (1.0f - m_weight) * m_input_A->m_anim_duration + m_weight * m_input_B->m_anim_duration;
+    } else {
+      assert (false);
+    }
+  }
+
+  virtual void UpdateTime(float dt) {
+    if (m_is_time_synced) {
+      float current_time_absolute = m_current_time * m_anim_duration + dt;
+      m_current_time = fmodf(current_time_absolute / m_anim_duration, 1.0);
+
+      m_input_A->UpdateTime(m_current_time - m_input_A->m_current_time);
+      m_input_B->UpdateTime(m_current_time - m_input_B->m_current_time);
+    } else {
+      m_current_time += dt;
+      m_input_A->UpdateTime(dt);
+      m_input_B->UpdateTime(dt);
+    }
   }
 
   virtual void Evaluate(

src/AnimNodes/SpeedScaleNode.cc

@@ -9,7 +9,16 @@
 void SpeedScaleNode::DrawDebugUi() {
   std::string node_name = "SpeedScaleNode: " + m_name;
   if (ImGui::TreeNode(node_name.c_str())) {
-    ImGui::SliderFloat("Time Scale", &m_time_scale, -5.f, 5.f);
+    bool is_negative = m_time_scale < 0.f;
+    if (ImGui::Checkbox("Reverse Time", &is_negative)) {
+      m_time_scale = m_time_scale * -1.f;
+    }
+
+    // ensure m_time_scale is positive
+    m_time_scale = m_time_scale * (is_negative ? -1.f : 1.f);
+    ImGui::SliderFloat("Time Scale", &m_time_scale, 0.01f, 5.f);
+    // and back to the original negative or positive sign
+    m_time_scale = m_time_scale * (is_negative ? -1.f : 1.f);
 
     m_input_node->DrawDebugUi();
 

src/AnimNodes/SpeedScaleNode.h

@@ -8,25 +8,43 @@
 #include "../AnimNode.h"
 
 struct SpeedScaleNode : public AnimNode {
-  SpeedScaleNode(AnimationController* animation_controller): AnimNode (animation_controller), m_time_scale(1.f) {}
+  SpeedScaleNode(AnimationController* animation_controller)
+      : AnimNode(animation_controller), m_time_scale(1.f) {
+    m_anim_node_type = AnimNodeType::SpeedScale;
+  }
 
   float m_time_scale;
   AnimNode* m_input_node;
 
-  virtual void Reset() {
-    m_current_time = 0.f;
+  virtual void Reset() { m_current_time = 0.f; }
+
+  virtual void UpdateIsSynced(bool is_synced) override {
+    m_is_time_synced = is_synced;
+    m_input_node->UpdateIsSynced(is_synced);
   }
 
-  virtual void Update(float dt) {
-    m_current_time += dt * m_time_scale;
-    m_input_node->Update(dt * m_time_scale);
+  virtual void EvalAnimDuration() override {
+    assert(fabs(m_time_scale) >= 0.01f);
+    m_anim_duration = fabsf(m_input_node->m_anim_duration / m_time_scale);
   }
 
-  virtual void Evaluate(ozz::vector<ozz::math::SoaTransform>* local_matrices) override {
+  virtual void UpdateTime(float dt) {
+    if (!m_is_time_synced) {
+      m_current_time += dt * m_time_scale;
+      m_input_node->UpdateTime(dt * m_time_scale);
+    } else {
+      m_current_time += dt;
+      m_input_node->UpdateTime(dt);
+    }
+  }
+
+  virtual void Evaluate(
+      ozz::vector<ozz::math::SoaTransform>* local_matrices) override {
     m_input_node->Evaluate(local_matrices);
   };
 
-  virtual void CollectNodeOrdering (std::vector<AnimNode*>& anim_nodes) override {
+  virtual void CollectNodeOrdering(
+      std::vector<AnimNode*>& anim_nodes) override {
     anim_nodes.push_back(this);
     m_input_node->CollectNodeOrdering(anim_nodes);
   }