Added comments and minor refactor.

src/AnimNode.h

@@ -9,11 +9,7 @@
 
 #include "AnimationController.h"
 
-enum class AnimNodeType {
-  Blend,
-  SpeedScale,
-  AnimSampler
-};
+enum class AnimNodeType { Blend, SpeedScale, AnimSampler };
 
 struct AnimNode {
   AnimNode(AnimationController* animation_controller)
@@ -25,24 +21,31 @@ struct AnimNode {
 
   AnimNodeType m_anim_node_type;
   std::string m_name;
-  float m_current_time;
-  bool m_is_time_synced;
-  float m_anim_duration;
   AnimationController* m_animation_controller;
-  ozz::vector<ozz::math::SoaTransform> m_local_matrices;
+
+  // When synced then current time is relative to the node's anim duration.:w
+  bool m_is_time_synced;
+  float m_current_time;
+  float m_anim_duration;
 
   virtual void Reset() { m_current_time = 0.f; }
 
+  // Mark current node according to is_synced and propagate flag to animation inputs.
   virtual void UpdateIsSynced(bool is_synced) = 0;
 
+  // Evaluate the animation duration of this node. All input nodes must have already evaluated
+  // their anim durations.
   virtual void EvalAnimDuration() = 0;
 
-  virtual void UpdateTime(float dt) { m_current_time += dt; }
+  // Evaluate current time and propagate time step to inputs.
+  virtual void UpdateTime(float dt) = 0;
 
+  // Evaluate the current node and write output to local_matrices.
   virtual void Evaluate(
       ozz::vector<ozz::math::SoaTransform>* local_matrices) = 0;
 
-  virtual void CollectNodeOrdering(std::vector<AnimNode*>& anim_nodes) = 0;
+  // Returns a list of animation nodes that provide input for this node.
+  virtual void GetInputNodes(std::vector<AnimNode*>& input_nodes) const = 0 ;
 
   virtual void DrawDebugUi(){};
 };

src/AnimNodes/AnimSamplerNode.h

@@ -22,6 +22,7 @@ struct AnimSamplerNode : public AnimNode {
   bool m_override_ratio;
   float m_anim_ratio;
 
+  ozz::vector<ozz::math::SoaTransform> m_local_matrices;
   ozz::animation::SamplingCache m_sampling_cache;
 
   void SetAnimation(ozz::animation::Animation* animation);
@@ -54,10 +55,7 @@ struct AnimSamplerNode : public AnimNode {
   virtual void Evaluate(
       ozz::vector<ozz::math::SoaTransform>* local_matrices) override;
 
-  virtual void CollectNodeOrdering(
-      std::vector<AnimNode*>& anim_nodes) override {
-    anim_nodes.push_back(this);
-  };
+  virtual void GetInputNodes(std::vector<AnimNode*>& input_nodes) const override{};
 
   virtual void DrawDebugUi();
 };

src/AnimNodes/BlendNode.h

@@ -60,11 +60,10 @@ struct BlendNode : public AnimNode {
   virtual void Evaluate(
       ozz::vector<ozz::math::SoaTransform>* local_matrices) override;
 
-  virtual void CollectNodeOrdering (std::vector<AnimNode*>& anim_nodes) override {
-    anim_nodes.push_back(this);
-    m_input_A->CollectNodeOrdering(anim_nodes);
-    m_input_B->CollectNodeOrdering(anim_nodes);
-  }
+  virtual void GetInputNodes(std::vector<AnimNode*>& input_nodes) const override {
+    input_nodes.push_back(m_input_A);
+    input_nodes.push_back(m_input_B);
+  };
 
   virtual void DrawDebugUi();
 };

src/AnimNodes/SpeedScaleNode.h

@@ -43,11 +43,9 @@ struct SpeedScaleNode : public AnimNode {
     m_input_node->Evaluate(local_matrices);
   };
 
-  virtual void CollectNodeOrdering(
-      std::vector<AnimNode*>& anim_nodes) override {
-    anim_nodes.push_back(this);
-    m_input_node->CollectNodeOrdering(anim_nodes);
-  }
+  virtual void GetInputNodes(std::vector<AnimNode*>& input_nodes) const override {
+      input_nodes.push_back(m_input_node);
+  };
 
   virtual void DrawDebugUi() override;
 };

src/AnimationController.cc

@@ -9,6 +9,8 @@
 #include <ozz/animation/runtime/local_to_model_job.h>
 #include <ozz/animation/runtime/sampling_job.h>
 
+#include <queue>
+
 #include "AnimNodes/AnimSamplerNode.h"
 #include "AnimNodes/BlendNode.h"
 #include "AnimNodes/SpeedScaleNode.h"
@@ -23,8 +25,6 @@ AnimationController::AnimationController(SkinnedMesh* skinned_mesh)
 
   m_local_matrices.resize(num_soa_joints);
 
-  assert(skinned_mesh->m_animations.size() > 1);
-  SetBlendAnims(skinned_mesh->m_animations[1], skinned_mesh->m_animations[0]);
   ResetAnims();
 
   AnimSamplerNode* sampler_node0 = new AnimSamplerNode(this);
@@ -56,7 +56,7 @@ AnimationController::AnimationController(SkinnedMesh* skinned_mesh)
 
   m_output_node = speed_node1;
 
-  m_output_node->CollectNodeOrdering(m_ordered_nodes);
+  UpdateOrderedNodes();
 
   m_output_node->Reset();
 }
@@ -78,13 +78,34 @@ void AnimationController::ResetAnims() {
   }
 }
 
+void AnimationController::UpdateOrderedNodes() {
+  std::vector<AnimNode*> node_stack;
+  node_stack.push_back(m_output_node);
+
+  m_ordered_nodes.clear();
+
+  while (node_stack.size() > 0) {
+    AnimNode* node = node_stack.back();
+    m_ordered_nodes.push_back(node);
+    node_stack.pop_back();
+
+    std::vector<AnimNode*> node_inputs;
+    node->GetInputNodes(node_inputs);
+    for (int i = node_inputs.size() - 1; i >= 0; i--) {
+      node_stack.push_back(node_inputs[i]);
+    }
+  }
+}
+
 void AnimationController::Update(float dt) {
   if (m_output_node == nullptr) {
     return;
   }
 
+  // Mark all nodes that evaluate time using sync tracks.
   m_output_node->UpdateIsSynced(false);
 
+  // For all synced nodes calculate their current sync track durations
   for (int i = m_ordered_nodes.size() - 1; i >= 0; i--) {
     AnimNode* node = m_ordered_nodes[i];
     if (node->m_is_time_synced) {
@@ -92,6 +113,7 @@ void AnimationController::Update(float dt) {
     }
   }
 
+  // Update the time of all nodes.
   m_output_node->UpdateTime(dt);
 }
 

src/AnimationController.h

@@ -18,13 +18,15 @@ struct AnimationController {
   explicit AnimationController(SkinnedMesh* skinned_mesh);
   virtual ~AnimationController();
 
-  void SetBlendAnims(
-      ozz::animation::Animation* blend_anim_A,
-      ozz::animation::Animation* blend_anim_B) {
-  }
   void ResetAnims();
 
+  // Creates a list of nodes where for node at index i for all inputs holds index > i.
+  void UpdateOrderedNodes();
+
+  // Updates all nodes.
   void Update(float dt);
+
+  // Recursively evaluates all nodes.
   void Evaluate();
 
   void DrawDebugUi();