Added graph design ramblings.

3rdparty/ozz-animation/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required (VERSION 3.3)
+cmake_minimum_required (VERSION 3.20)
 
 # Defines the project's name
 project(ozz)

3rdparty/ozz-animation/include/ozz/base/containers/std_allocator.h

@@ -49,7 +49,7 @@ class StdAllocator {
   StdAllocator(const StdAllocator&) noexcept {}
 
   template <class _Other>
-  StdAllocator<value_type>(const StdAllocator<_Other>&) noexcept {}
+  StdAllocator(const StdAllocator<_Other>&) noexcept {}
 
   template <class _Other>
   struct rebind {

CMakeLists.txt

@@ -44,10 +44,13 @@ add_library(AnimTestbedCode OBJECT
         src/Camera.c
         src/SkinnedMesh.cc
         src/SkinnedMesh.h
+        src/SyncTrack.cc
+        src/SyncTrack.h
         src/AnimNode.cc
         src/AnimNodes/AnimSamplerNode.cc
         src/AnimNodes/SpeedScaleNode.cc
         src/AnimNodes/BlendNode.cc
+        src/AnimNodes/LockTranslationNode.cc
         src/AnimationController.cc
         3rdparty/imgui/imgui.cpp
         3rdparty/imgui/imgui_draw.cpp

doc/design.md

@@ -0,0 +1,35 @@
+## Graph
+
+### 1. Support of math nodes (or non-AnimNodes in general)
+
+* Enables animators to add custom math for blend inputs or to adjust other inputs (e.g. LookAt or IK
+  targets).
+
+**Open Issues**
+
+1. When to do the evaluation? Two types of subgraphs:
+   a) Instant inputs (needed for blend node inputs) that have to be evaluated before
+   UpdateConnections
+   b) Processing nodes, e.g. for extracted bones.
+
+### 2. Support of multiple output sockets
+
+* E.g. extract Bone transform
+
+* Increases Node complexity:
+    * AnimOutput
+    * AnimOutput + Data
+    * Data
+
+(Data = bool, float, vec3, quat, ...)
+
+**Open Issues**
+
+1. Unclear when this is actually needed. Using more specific nodes that perform the desired logic
+   may be better (
+   c.f. https://dev.epicgames.com/documentation/en-us/unreal-engine/animation-blueprint-bone-driven-controller-in-unreal-engine).
+   Likely this is not crucial so should be avoided for now.
+
+### 3. Multi-skeleton evaluation
+
+Use case: riding on a horse, interaction between two characters.

src/AnimNode.h

@@ -16,8 +16,7 @@ struct AnimNode {
   AnimNode(AnimationController* animation_controller)
       : m_animation_controller(animation_controller),
         m_current_time(0.f),
-        m_is_time_synced(false),
-        m_anim_duration(0.f) {}
+        m_is_time_synced(false) {}
   virtual ~AnimNode(){};
 
   AnimNodeType m_anim_node_type;
@@ -27,7 +26,6 @@ struct AnimNode {
   // 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;
   SyncTrack m_sync_track;
 
   virtual void Reset() { m_current_time = 0.f; }
@@ -37,7 +35,7 @@ struct AnimNode {
 
   // Evaluate the animation duration of this node. All input nodes must have already evaluated
   // their anim durations.
-  virtual void EvalAnimDuration() = 0;
+  virtual void UpdateSyncTrack() = 0;
 
   // Evaluate current time and propagate time step to inputs.
   virtual void UpdateTime(float dt) = 0;

src/AnimNodes/AnimSamplerNode.cc

@@ -8,7 +8,7 @@
 
 #include "../SkinnedMesh.h"
 
-void AnimSamplerNode::SetAnimation(ozz::animation::Animation* animation) {
+void AnimSamplerNode::SetAnimation(ozz::animation::Animation* animation, const SyncTrack& sync_track) {
   m_animation = animation;
 
   const SkinnedMesh* skinned_mesh = m_animation_controller->m_skinned_mesh;
@@ -16,11 +16,12 @@ void AnimSamplerNode::SetAnimation(ozz::animation::Animation* animation) {
   const int num_joints = skinned_mesh->m_skeleton.num_joints();
   m_local_matrices.resize(num_soa_joints);
   m_sampling_cache.Resize(num_joints);
+
+  m_sync_track = sync_track;
 }
 
-
-
-void AnimSamplerNode::Evaluate(ozz::vector<ozz::math::SoaTransform>* local_matrices) {
+void AnimSamplerNode::Evaluate(
+    ozz::vector<ozz::math::SoaTransform>* local_matrices) {
   ozz::animation::SamplingJob sampling_job;
   sampling_job.animation = m_animation;
   sampling_job.cache = &m_sampling_cache;
@@ -31,11 +32,7 @@ void AnimSamplerNode::Evaluate(ozz::vector<ozz::math::SoaTransform>* local_matri
   }
 }
 
-
-
 void AnimSamplerNode::DrawDebugUi() {
-  std::string node_name = "AnimSamplerNode: " + m_name;
-  if (ImGui::TreeNode(node_name.c_str())) {
   const SkinnedMesh* skinned_mesh = m_animation_controller->m_skinned_mesh;
   int anim_count = skinned_mesh->m_animation_names.size();
   const char* items[255] = {0};
@@ -49,11 +46,13 @@ void AnimSamplerNode::DrawDebugUi() {
 
   if (ImGui::Combo("Animation", &item_current, items, anim_count)) {
     m_animation = skinned_mesh->m_animations[item_current];
+    m_sync_track = skinned_mesh->m_animation_sync_track[item_current];
   }
+
   ImGui::Checkbox("Override", &m_override_ratio);
   ImGui::SameLine();
   ImGui::SliderFloat("Ratio", &m_anim_ratio, 0.f, 1.f);
 
-    ImGui::TreePop();
-  }
+  ImGui::Text("SyncTrack");
+  m_sync_track.DrawDebugUi();
 }

src/AnimNodes/AnimSamplerNode.h

@@ -25,25 +25,22 @@ struct AnimSamplerNode : public AnimNode {
   ozz::vector<ozz::math::SoaTransform> m_local_matrices;
   ozz::animation::SamplingCache m_sampling_cache;
 
-  void SetAnimation(ozz::animation::Animation* animation);
+  void SetAnimation(ozz::animation::Animation* animation, const SyncTrack& sync_track);
 
   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 UpdateSyncTrack() override {
   }
 
   virtual void UpdateTime(float dt) override {
     m_current_time += dt;
     if (!m_override_ratio) {
       if (m_is_time_synced) {
-        m_anim_ratio = fmodf((float)m_current_time, 1.0f);
-        m_current_time = m_anim_ratio;
+        m_anim_ratio = m_sync_track.CalcRatioFromSyncTime(m_current_time);
       } else {
-        const float duration = m_animation->duration();
-        m_anim_ratio = fmodf((float)m_current_time / duration, 1.0f);
+        m_anim_ratio = fmodf((float)m_current_time / m_animation->duration(), 1.0f);
       }
     }
 

src/AnimNodes/BlendNode.cc

@@ -49,14 +49,11 @@ void BlendNode::Evaluate(ozz::vector<ozz::math::SoaTransform>* local_matrices) {
 }
 
 void BlendNode::DrawDebugUi() {
-  std::string node_name = "BlendNode: " + m_name;
-  if (ImGui::TreeNode(node_name.c_str())) {
-    ImGui::Text("Input A:");
-    m_input_A->DrawDebugUi();
-    ImGui::Text("Input B:");
-    m_input_B->DrawDebugUi();
-    ImGui::SliderFloat("Weight", &m_weight, 0.f, 1.f);
+  if (ImGui::SliderFloat("Weight", &m_weight, 0.f, 1.f)) {
+    m_sync_track = SyncTrack::Blend(m_weight, m_input_A->m_sync_track, m_input_B->m_sync_track);
+  }
   ImGui::Checkbox("Sync Inputs", &m_sync_inputs);
-    ImGui::TreePop();
-  }
+
+  ImGui::Text("SyncTrack");
+  m_sync_track.DrawDebugUi();
 }

src/AnimNodes/BlendNode.h

@@ -35,9 +35,9 @@ struct BlendNode : public AnimNode {
     m_input_A->UpdateIsSynced(m_is_time_synced);
   }
 
-  virtual void EvalAnimDuration() override {
+  virtual void UpdateSyncTrack() 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;
+      m_sync_track = SyncTrack::Blend(m_weight, m_input_A->m_sync_track, m_input_B->m_sync_track);
     } else {
       assert (false);
     }
@@ -45,11 +45,11 @@ struct BlendNode : public AnimNode {
 
   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_current_time = fmodf(m_current_time + dt, m_sync_track.m_duration);
+      float current_sync_time = m_sync_track.CalcSyncFromAbsTime(m_current_time);
 
-      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);
+      m_input_A->UpdateTime(current_sync_time - m_input_A->m_current_time);
+      m_input_B->UpdateTime(current_sync_time - m_input_B->m_current_time);
     } else {
       m_current_time += dt;
       m_input_A->UpdateTime(dt);

src/AnimNodes/LockTranslationNode.cc

@@ -0,0 +1,59 @@
+//
+// Created by martin on 16.11.21.
+//
+
+#include "LockTranslationNode.h"
+
+#include <imgui.h>
+#include "ozz/base/maths/soa_transform.h"
+
+void LockTranslationNode::Evaluate(
+    ozz::vector<ozz::math::SoaTransform>* local_matrices) {
+  m_input->Evaluate(local_matrices);
+  ozz::math::SoaFloat3 translation = (*local_matrices)[m_locked_bone_index].translation;
+  float x[4];
+  float y[4];
+  float z[4];
+  _mm_store_ps(x, translation.x);
+  _mm_store_ps(y, translation.y);
+  _mm_store_ps(z, translation.z);
+
+  if (m_lock_x) {
+    x[0] = 0.f;
+  }
+
+  if (m_lock_y) {
+    y[0] = 0.f;
+  }
+
+  if (m_lock_z) {
+    z[0] = 0.f;
+  }
+
+  translation.x = _mm_load_ps(x);
+  translation.y = _mm_load_ps(y);
+  translation.z = _mm_load_ps(z);
+
+  //translation = ozz::math::SoaFloat3::zero();
+//  ozz::math::SetX(translation, 0.f);
+//  ozz::math::SetZ(translation, 0.f);
+   (*local_matrices)[m_locked_bone_index].translation = translation;
+}
+
+void LockTranslationNode::DrawDebugUi() {
+  const ozz::animation::Skeleton& skeleton = m_animation_controller->m_skinned_mesh->m_skeleton;
+  ozz::span<const char* const> joint_names = skeleton.joint_names();
+
+  const char* items[255] = {0};
+  int item_current = 0;
+  for (int i = 0; i < joint_names.size(); i++) {
+    items[i] = joint_names[i];
+  }
+
+  ImGui::Combo("Bone", &m_locked_bone_index, items, joint_names.size());
+  ImGui::Checkbox("Lock X", &m_lock_x);
+  ImGui::Checkbox("Lock Y", &m_lock_y);
+  ImGui::Checkbox("Lock Z", &m_lock_z);
+
+
+}

src/AnimNodes/LockTranslationNode.h

@@ -0,0 +1,52 @@
+//
+// Created by martin on 16.11.21.
+//
+
+#ifndef ANIMTESTBED_LOCKBONES_H
+#define ANIMTESTBED_LOCKBONES_H
+
+#include "../AnimNode.h"
+
+struct LockTranslationNode : public AnimNode {
+  LockTranslationNode(AnimationController* animation_controller)
+      : AnimNode(animation_controller),
+        m_input(nullptr),
+        m_locked_bone_index(0),
+        m_lock_x(false),
+        m_lock_y(false),
+        m_lock_z(false) {}
+
+  virtual ~LockTranslationNode() {}
+
+  AnimNode* m_input;
+  int m_locked_bone_index;
+  bool m_lock_x;
+  bool m_lock_y;
+  bool m_lock_z;
+
+  virtual void Reset() { m_current_time = 0.f; }
+
+  virtual void UpdateIsSynced(bool is_synced) override {
+    m_is_time_synced = is_synced;
+
+    m_input->UpdateIsSynced(m_is_time_synced);
+  }
+
+  virtual void UpdateSyncTrack() override {
+    m_sync_track = m_input->m_sync_track;
+  }
+
+  virtual void UpdateTime(float dt) { m_input->UpdateTime(dt); }
+
+  virtual void Evaluate(
+      ozz::vector<ozz::math::SoaTransform>* local_matrices) override;
+
+  virtual void GetInputNodes(
+      std::vector<AnimNode*>& input_nodes) const override {
+    input_nodes.push_back(m_input);
+  };
+
+  virtual void DrawDebugUi() override;
+};
+
+#endif  //ANIMTESTBED_LOCKBONES_H

src/AnimNodes/SpeedScaleNode.cc

@@ -7,8 +7,6 @@
 #include <imgui.h>
 
 void SpeedScaleNode::DrawDebugUi() {
-  std::string node_name = "SpeedScaleNode: " + m_name;
-  if (ImGui::TreeNode(node_name.c_str())) {
   bool is_negative = m_time_scale < 0.f;
   if (ImGui::Checkbox("Reverse Time", &is_negative)) {
     m_time_scale = m_time_scale * -1.f;
@@ -16,12 +14,11 @@ void SpeedScaleNode::DrawDebugUi() {
 
   // 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);
+  if (ImGui::SliderFloat("Time Scale", &m_time_scale, 0.01f, 2.f)) {
+    if (fabs(m_time_scale - 1.0) < 0.2) {
+      m_time_scale = 1.0;
+    }
+  }
   // 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();
-
-    ImGui::TreePop();
-  }
 }

src/AnimNodes/SpeedScaleNode.h

@@ -23,9 +23,10 @@ struct SpeedScaleNode : public AnimNode {
     m_input_node->UpdateIsSynced(is_synced);
   }
 
-  virtual void EvalAnimDuration() override {
+  virtual void UpdateSyncTrack() override {
     assert(fabs(m_time_scale) >= 0.01f);
-    m_anim_duration = fabsf(m_input_node->m_anim_duration / m_time_scale);
+    m_sync_track = m_input_node->m_sync_track;
+    m_sync_track.m_duration =fabsf(m_input_node->m_sync_track.m_duration / m_time_scale);
   }
 
   virtual void UpdateTime(float dt) {

src/AnimationController.cc

@@ -5,7 +5,6 @@
 #include "AnimationController.h"
 
 #include <imgui.h>
-#include <ozz/animation/runtime/blending_job.h>
 #include <ozz/animation/runtime/local_to_model_job.h>
 #include <ozz/animation/runtime/sampling_job.h>
 
@@ -13,28 +12,27 @@
 
 #include "AnimNodes/AnimSamplerNode.h"
 #include "AnimNodes/BlendNode.h"
+#include "AnimNodes/LockTranslationNode.h"
 #include "AnimNodes/SpeedScaleNode.h"
 #include "SkinnedMesh.h"
 
 AnimationController::AnimationController(SkinnedMesh* skinned_mesh)
-    : m_current_time(0.f), m_skinned_mesh(skinned_mesh) {
+    : m_current_time(0.f), m_paused(true), m_skinned_mesh(skinned_mesh) {
   const int num_soa_joints = skinned_mesh->m_skeleton.num_soa_joints();
   const int num_joints = skinned_mesh->m_skeleton.num_joints();
   skinned_mesh->m_local_matrices.resize(num_soa_joints);
   skinned_mesh->m_model_matrices.resize(num_joints);
 
-  m_local_matrices.resize(num_soa_joints);
-
   ResetAnims();
 
   AnimSamplerNode* sampler_node0 = new AnimSamplerNode(this);
   sampler_node0->m_name = "AnimSampler0";
-  sampler_node0->SetAnimation(skinned_mesh->m_animations[1]);
+  sampler_node0->SetAnimation(skinned_mesh->m_animations[1], skinned_mesh->m_animation_sync_track[1]);
   m_anim_nodes.push_back(sampler_node0);
 
   AnimSamplerNode* sampler_node1 = new AnimSamplerNode(this);
   sampler_node1->m_name = "AnimSampler1";
-  sampler_node1->SetAnimation(skinned_mesh->m_animations[2]);
+  sampler_node1->SetAnimation(skinned_mesh->m_animations[2], skinned_mesh->m_animation_sync_track[2]);
   m_anim_nodes.push_back(sampler_node1);
 
   SpeedScaleNode* speed_node = new SpeedScaleNode(this);
@@ -46,7 +44,7 @@ AnimationController::AnimationController(SkinnedMesh* skinned_mesh)
   blend_node->m_name = "Blend0";
   blend_node->m_input_A = speed_node;
   blend_node->m_input_B = sampler_node1;
-  blend_node->m_sync_inputs = false;
+  blend_node->m_sync_inputs = true;
   m_anim_nodes.push_back(blend_node);
 
   SpeedScaleNode* speed_node1 = new SpeedScaleNode(this);
@@ -54,15 +52,19 @@ AnimationController::AnimationController(SkinnedMesh* skinned_mesh)
   speed_node1->m_input_node = blend_node;
   m_anim_nodes.push_back(speed_node1);
 
-  m_output_node = speed_node1;
+  LockTranslationNode* lock_node = new LockTranslationNode(this);
+  lock_node->m_name = "LockNode0";
+  lock_node->m_locked_bone_index = 0;
+  lock_node->m_input = speed_node1;
+  m_anim_nodes.push_back(lock_node);
+
+  m_output_node = m_anim_nodes.back();
 
   UpdateOrderedNodes();
 
   m_output_node->Reset();
 }
 
-
-
 AnimationController::~AnimationController() {
   while (m_anim_nodes.size() > 0) {
     delete m_anim_nodes[m_anim_nodes.size() - 1];
@@ -97,12 +99,8 @@ void AnimationController::UpdateOrderedNodes() {
   }
 }
 
-void AnimationController::UpdateBlendLogic() {
-
-}
-
 void AnimationController::UpdateTime(float dt) {
-  if (m_output_node == nullptr) {
+  if (m_paused || m_output_node == nullptr) {
     return;
   }
 
@@ -113,7 +111,7 @@ void AnimationController::UpdateTime(float dt) {
   for (int i = m_ordered_nodes.size() - 1; i >= 0; i--) {
     AnimNode* node = m_ordered_nodes[i];
     if (node->m_is_time_synced) {
-      node->EvalAnimDuration();
+      node->UpdateSyncTrack();
     }
   }
 
@@ -121,24 +119,14 @@ void AnimationController::UpdateTime(float dt) {
   m_output_node->UpdateTime(dt);
 }
 
-
-
 void AnimationController::Evaluate() {
   if (m_output_node == nullptr) {
     return;
   }
-  m_output_node->Evaluate(&m_local_matrices);
 
-  // convert joint matrices from local to model space
-  ozz::animation::LocalToModelJob ltm_job;
-  ltm_job.skeleton = &m_skinned_mesh->m_skeleton;
-  ltm_job.input = make_span(m_local_matrices);
-  ltm_job.output = make_span(m_skinned_mesh->m_model_matrices);
-  ltm_job.Run();
+  m_output_node->Evaluate(&m_skinned_mesh->m_local_matrices);
 };
 
-
-
 void AnimationController::DrawDebugUi() {
   ImGui::SetNextWindowSize(ImVec2(500, 300), ImGuiCond_FirstUseEver);
   ImGui::Begin("AnimationController");
@@ -146,47 +134,80 @@ void AnimationController::DrawDebugUi() {
   if (ImGui::Button("Reset")) {
     ResetAnims();
   }
-
-  if (m_output_node && ImGui::TreeNode("Output")) {
-    m_output_node->DrawDebugUi();
-
-    ImGui::TreePop();
+  ImGui::SameLine();
+  if (m_paused) {
+    if (ImGui::Button("Play")) {
+      m_paused = false;
+    }
+  } else {
+    if (ImGui::Button("Pause")) {
+      m_paused = true;
+    }
+  }
+  ImGui::SameLine();
+  if (ImGui::Button("Step")) {
+    bool was_paused = m_paused;
+    m_paused = false;
+    UpdateTime(0.1);
+    Evaluate();
+    m_paused = was_paused;
   }
 
-  if (m_output_node && ImGui::TreeNode("Nodes")) {
-    ImGui::Columns(4, "NodeOverview"); // 4-ways, with border
+  ImVec2 node_size(200, 100);
+  for (int i = 0; i < m_ordered_nodes.size(); i++) {
+    AnimNode* node = m_ordered_nodes[i];
+
+    ImGui::SetNextWindowSize(node_size, ImGuiCond_FirstUseEver);
+    ImGui::SetNextWindowPos(
+        ImVec2((m_ordered_nodes.size() - 1 - i) * node_size.x - i * 10, 300),
+        ImGuiCond_FirstUseEver);
+    ImGui::Begin(node->m_name.c_str());
+    node->DrawDebugUi();
+    ImGui::End();
+  }
+
+  ImGui::Text ("Node States");
+
+  ImGui::Columns(4, "Node States");  // 4-ways, with border
   ImGui::Separator();
-    ImGui::Text("Name"); ImGui::NextColumn();
-    ImGui::Text("Synced"); ImGui::NextColumn();
-    ImGui::Text("Duration"); ImGui::NextColumn();
-    ImGui::Text("Time"); ImGui::NextColumn();
+  ImGui::Text("Name");
+  ImGui::NextColumn();
+  ImGui::Text("Synced");
+  ImGui::NextColumn();
+  ImGui::Text("Duration");
+  ImGui::NextColumn();
+  ImGui::Text("Time");
+  ImGui::NextColumn();
 
   ImGui::Separator();
   static int selected = -1;
 
   for (int i = 0; i < m_ordered_nodes.size(); i++) {
     AnimNode* node = m_ordered_nodes[i];
-      if (ImGui::Selectable(node->m_name.c_str(), selected == i, ImGuiSelectableFlags_SpanAllColumns))
+    if (ImGui::Selectable(
+            node->m_name.c_str(),
+            selected == i,
+            ImGuiSelectableFlags_SpanAllColumns))
       selected = i;
     bool hovered = ImGui::IsItemHovered();
     ImGui::NextColumn();
 
-      ImGui::Text(node->m_is_time_synced ? "X" : "-"); ImGui::NextColumn();
+    ImGui::Text(node->m_is_time_synced ? "X" : "-");
+    ImGui::NextColumn();
 
-      ImGui::PushID((void*)&node->m_anim_duration);
-      ImGui::Text("%2.3f", node->m_anim_duration);      ImGui::NextColumn();
+    ImGui::PushID((void*)&node->m_sync_track.m_duration);
+    ImGui::Text("%2.3f", node->m_sync_track.m_duration);
+    ImGui::NextColumn();
     ImGui::PopID();
 
     ImGui::PushID((void*)&node->m_current_time);
-      ImGui::Text("%2.3f", node->m_current_time);      ImGui::NextColumn();
+    ImGui::Text("%2.3f", node->m_current_time);
+    ImGui::NextColumn();
     ImGui::PopID();
   }
 
   ImGui::Columns(1);
   ImGui::Separator();
 
-    ImGui::TreePop();
-  }
-
   ImGui::End();
 }

src/AnimationController.h

@@ -23,8 +23,6 @@ struct AnimationController {
   // Creates a list of nodes where for node at index i for all inputs holds index > i.
   void UpdateOrderedNodes();
 
-  void UpdateBlendLogic();
-
   // Updates all nodes.
   void UpdateTime(float dt);
 
@@ -34,11 +32,7 @@ struct AnimationController {
   void DrawDebugUi();
 
   float m_current_time;
-
-  ozz::vector<ozz::math::SoaTransform> m_local_matrices;
-  ozz::vector<ozz::math::SoaTransform> m_local_matrices_blended;
-
-  ozz::animation::SamplingCache m_sampling_cache_A;
+  bool m_paused;
 
   SkinnedMesh* m_skinned_mesh = nullptr;
 

src/Camera.c

@@ -42,8 +42,8 @@ inline void Camera_Init(Camera* camera) {
   camera->pitch = 10 * M_PI / 180.0f;
 
   memcpy(&camera->mtxView, &mtx_identity, sizeof(camera->mtxView));
-  Camera_CalcToMatrix(camera, &camera->mtxView);
-  Camera_CalcFromMatrix(camera, &camera->mtxView);
+  Camera_CalcToMatrix(camera, &camera->mtxView[0]);
+  Camera_CalcFromMatrix(camera, &camera->mtxView[0]);
 }
 
 void Camera_CalcFromMatrix(Camera* camera, float* mat) {
@@ -153,6 +153,6 @@ inline void Camera_Update(
       camera->vel[i] = camera->vel[i] * 0.1;
     }
 
-    Camera_CalcToMatrix(camera, &camera->mtxView);
+    Camera_CalcToMatrix(camera, &camera->mtxView[0]);
   }
 }

src/SkinnedMesh.cc

@@ -7,7 +7,6 @@
 #include <HandmadeMath.h>
 #include <imgui.h>
 
-
 SkinnedMesh::~SkinnedMesh() {
   while (m_animations.size() > 0) {
     ozz::animation::Animation* animation_ptr =
@@ -76,6 +75,7 @@ bool SkinnedMesh::LoadAnimation(const char* filename) {
 
   m_animations.push_back(animation_ptr);
   m_animation_names.push_back(filename);
+  m_animation_sync_track.push_back(SyncTrack());
 
   return true;
 }
@@ -89,20 +89,7 @@ void SkinnedMesh::SetCurrentAnimation(int index) {
   m_current_animation = m_animations[index];
 }
 
-//bool LoadMesh (const char* filename);
-
-void SkinnedMesh::EvalAnimation(float in_time) {
-  const float anim_duration = m_current_animation->duration();
-  float anim_ratio = fmodf((float)in_time / anim_duration, 1.0f);
-
-  // sample animation
-  ozz::animation::SamplingJob sampling_job;
-  sampling_job.animation = m_current_animation;
-  sampling_job.cache = &m_cache;
-  sampling_job.ratio = anim_ratio;
-  sampling_job.output = make_span(m_local_matrices);
-  sampling_job.Run();
-
+void SkinnedMesh::CalcModelMatrices() {
   // convert joint matrices from local to model space
   ozz::animation::LocalToModelJob ltm_job;
   ltm_job.skeleton = &m_skeleton;
@@ -111,27 +98,40 @@ void SkinnedMesh::EvalAnimation(float in_time) {
   ltm_job.Run();
 }
 
-void SkinnedMesh::DrawSkeleton() {
-
-}
+void SkinnedMesh::DrawSkeleton() {}
 
 void SkinnedMesh::DrawDebugUi() {
   ImGui::Begin("SkinnedMesh");
 
-//  ImGui::Checkbox("Time override", &state.time.anim_ratio_ui_override);
+  ImGui::Text("Animations");
 
-  //  const float anim_duration = state.ozz->animation.duration();
-  //  if (!state.time.anim_ratio_ui_override) {
-  //    state.time.anim_ratio =
-  //        fmodf((float)state.time.absolute / anim_duration, 1.0f);
-  //  }
-  //  ImGui::SliderFloat("Time", &state.time.anim_ratio, 0.f, 1.f);
+  const char* items[255] = {0};
+  static int selected = -1;
+  for (int i = 0; i < m_animations.size(); i++) {
+    items[i] = m_animation_names[i].c_str();
+  }
 
-//  ImGui::Text(
-//      "Application average %.3f ms/frame (%.1f FPS)",
-//      1000.0f / ImGui::GetIO().Framerate,
-//      ImGui::GetIO().Framerate);
+  ImGui::Combo("Animation", &selected, items, m_animations.size());
+
+  ImGui::Text("Sync Track");
+  if (selected >= 0 && selected < m_animations.size()) {
+    m_animation_sync_track[selected].DrawDebugUi();
+    m_override_anim = selected;
+
+    ImGui::Checkbox("Override Animation", &m_sync_track_override);
+    if (m_sync_track_override) {
+      ImGui::SliderFloat("Ratio", &m_override_ratio, 0.f, 1.f);
+
+      ozz::animation::SamplingJob sampling_job;
+      sampling_job.animation = m_animations[selected];
+      sampling_job.cache = &m_cache;
+      sampling_job.ratio = m_override_ratio;
+      sampling_job.output = make_span(m_local_matrices);
+      if (!sampling_job.Run()) {
+        ozz::log::Err() << "Error sampling animation." << std::endl;
+      }
+    }
+  }
 
   ImGui::End();
-
 }

src/SkinnedMesh.h

@@ -9,6 +9,7 @@
 #include <cmath>   // fmodf
 #include <memory>  // std::unique_ptr, std::make_unique
 
+#include "SyncTrack.h"
 #include "ozz/animation/runtime/animation.h"
 #include "ozz/animation/runtime/local_to_model_job.h"
 #include "ozz/animation/runtime/sampling_job.h"
@@ -20,51 +21,23 @@
 #include "ozz/base/maths/soa_transform.h"
 #include "ozz/base/maths/vec_float.h"
 
-constexpr int cSyncTrackMaxIntervals = 8;
-
-struct SyncTrack {
-  float m_duration;
-  int m_num_intervals;
-  float m_interval_durations[cSyncTrackMaxIntervals];
-
-  float ConvertAbsTimeToSyncTime (float abs_time) {
-    float sync_time = fmodf (abs_time, m_duration) / m_duration;
-
-    int interval_index = 0;
-    while (sync_time < m_interval_durations[interval_index]) {
-      sync_time -= m_interval_durations[interval_index];
-      interval_index ++;
-    }
-  }
-
-  static SyncTrack Blend(float weight, const SyncTrack& track_A, const SyncTrack& track_B) {
-    SyncTrack result;
-
-    assert (track_A.m_num_intervals == track_B.m_num_intervals);
-    result.m_num_intervals = track_A.m_num_intervals;
-
-    result.m_duration = (1.0f - weight) * track_A.m_duration + weight * track_B.m_duration;
-
-    for (int i = 0; i < result.m_num_intervals; i++) {
-      result.m_interval_durations[i] = (1.0f - weight) * track_A.m_interval_durations[i] + weight * track_B.m_interval_durations[i];
-    }
-
-    return result;
-  }
-};
-
-
 struct SkinnedMesh {
+  SkinnedMesh() : m_sync_track_override(false), m_override_anim(0.f) {}
   virtual ~SkinnedMesh();
+
   bool LoadSkeleton(const char* filename);
   bool LoadAnimation(const char* filename);
   //bool LoadMesh (const char* filename);
 
   void SetCurrentAnimation(int index);
-  const ozz::animation::Animation* GetCurrentAnimation() {return m_current_animation; };
-  float GetCurrentAnimationDuration() {return m_current_animation->duration(); };
+  const ozz::animation::Animation* GetCurrentAnimation() {
+    return m_current_animation;
+  };
+  float GetCurrentAnimationDuration() {
+    return m_current_animation->duration();
+  };
 
-  void EvalAnimation(float in_time);
+  void CalcModelMatrices();
   void DrawSkeleton();
   void DrawJoint(int joint_index, int parent_joint_index);
 
@@ -79,6 +52,10 @@ struct SkinnedMesh {
   ozz::animation::SamplingCache m_cache;
   ozz::vector<ozz::math::SoaTransform> m_local_matrices;
   ozz::vector<ozz::math::Float4x4> m_model_matrices;
+
+  bool m_sync_track_override;
+  int m_override_anim;
+  float m_override_ratio;
 };
 
 #endif  //ANIMTESTBED_SKINNEDMESH_H

src/SyncTrack.cc

@@ -0,0 +1,46 @@
+//
+// Created by martin on 19.11.21.
+//
+
+#include "SyncTrack.h"
+
+#include <imgui.h>
+
+#include <sstream>
+
+void SyncTrack::DrawDebugUi() {
+  ImGui::SliderFloat("duration", &m_duration, 0.001f, 10.f);
+
+  ImGui::Text("Marker");
+  ImGui::SameLine();
+  ImGui::Text("%d", m_num_intervals);
+  ImGui::SameLine();
+  if (ImGui::Button("+")) {
+    if (m_num_intervals < cSyncTrackMaxIntervals) {
+      m_num_intervals ++;
+    }
+  }
+  ImGui::SameLine();
+  if (ImGui::Button("-")) {
+    if (m_num_intervals > 0) {
+      m_num_intervals --;
+    }
+  }
+
+  ImGui::Text("Marker:");
+  for (int i = 0; i < m_num_intervals; i++) {
+    ImGui::Text("%2d:", i);
+    ImGui::SameLine();
+    std::ostringstream marker_stream;
+    marker_stream << i;
+    ImGui::SliderFloat(
+        marker_stream.str().c_str(),
+        &m_sync_markers[i],
+        0.f,
+        1.f);
+  }
+
+  if (ImGui::Button ("Update Intervals")) {
+    CalcIntervals();
+  }
+}

src/SyncTrack.h

@@ -0,0 +1,156 @@
+//
+// Created by martin on 19.11.21.
+//
+
+#ifndef ANIMTESTBED_SYNCTRACK_H
+#define ANIMTESTBED_SYNCTRACK_H
+
+#include <cassert>
+#include <cmath>
+
+constexpr int cSyncTrackMaxIntervals = 8;
+
+struct SyncTrack {
+  SyncTrack() : m_duration(0.f), m_num_intervals(0) {
+    for (int i = 0; i < cSyncTrackMaxIntervals; i++) {
+      m_sync_markers[i] = 0.f;
+      m_interval_ratio[i] = 0.f;
+      m_interval_ratio[i] = 0.f;
+    }
+  }
+
+  float m_duration;
+  int m_num_intervals;
+  float m_sync_markers[cSyncTrackMaxIntervals];
+  float m_interval_start[cSyncTrackMaxIntervals];
+  float m_interval_ratio[cSyncTrackMaxIntervals];
+
+  void CalcIntervals() {
+    if (m_num_intervals == 0) {
+      m_num_intervals = 1;
+      m_sync_markers[0] = 0.f;
+    }
+    for (int i = 0; i < m_num_intervals; i++) {
+      assert(m_sync_markers[i] >= 0.f && m_sync_markers[i] <= 1.0f);
+
+      int end_index = i < m_num_intervals - 1 ? i + 1 : 0;
+
+      m_interval_start[i] = m_sync_markers[i];
+      float interval_end = m_sync_markers[end_index];
+
+      if (interval_end < m_interval_start[i]) {
+        interval_end += 1.0f;
+      }
+
+      m_interval_ratio[i] = interval_end - m_interval_start[i];
+    }
+  }
+
+  float CalcSyncFromAbsTime(float abs_time) {
+    float sync_time = fmodf(abs_time, m_duration) / m_duration;
+
+    int interval_index = 0;
+    while (sync_time >= m_interval_ratio[interval_index]) {
+      sync_time -= m_interval_ratio[interval_index];
+      interval_index++;
+    }
+
+    return float(interval_index) + sync_time / m_interval_ratio[interval_index];
+  }
+
+  float CalcRatioFromSyncTime(float sync_time) {
+    float interval_ratio = fmodf(sync_time, 1.0f);
+    int interval = int(sync_time - interval_ratio);
+
+    return fmodf(
+        m_interval_start[interval]
+            + m_interval_ratio[interval] * interval_ratio,
+        1.0f);
+  }
+
+  bool operator==(const SyncTrack& other) const {
+    bool result = m_duration == other.m_duration
+                  && m_num_intervals == other.m_num_intervals;
+
+    if (!result) {
+      return false;
+    }
+
+    for (int i = 0; i < m_num_intervals; i++) {
+      if ((fabsf(m_interval_start[i] - other.m_interval_start[i]) > 1.0e-5)
+          || (fabsf(m_interval_ratio[i] - other.m_interval_ratio[i])
+              > 1.0e-5)) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  static SyncTrack CreateFromMarkers(
+      float duration,
+      int n_markers,
+      float markers[cSyncTrackMaxIntervals]) {
+    SyncTrack result;
+    result.m_duration = duration;
+    result.m_num_intervals = n_markers;
+    for (int i = 0; i < n_markers; i++) {
+      result.m_sync_markers[i] = markers[i];
+    }
+
+    result.CalcIntervals();
+
+    return result;
+  }
+
+  static SyncTrack
+  Blend(float weight, const SyncTrack& track_A, const SyncTrack& track_B) {
+    assert(track_A.m_num_intervals == track_B.m_num_intervals);
+
+    SyncTrack result;
+    result.m_num_intervals = track_A.m_num_intervals;
+
+    result.m_duration =
+        (1.0f - weight) * track_A.m_duration + weight * track_B.m_duration;
+
+    float interval_0_offset =
+        track_B.m_interval_start[0] - track_A.m_interval_start[0];
+    if (interval_0_offset > 0.5f) {
+      interval_0_offset = -fmodf(1.f - interval_0_offset, 1.0f);
+    } else if (interval_0_offset < -0.5) {
+      interval_0_offset = fmodf(1.f + interval_0_offset, 1.0f);
+    }
+
+    result.m_interval_start[0] = fmodf(
+        1.0 + (1.0f - weight) * track_A.m_interval_start[0]
+            + weight * (track_A.m_interval_start[0] + interval_0_offset),
+        1.0f);
+    result.m_sync_markers[0] = result.m_interval_start[0];
+
+    for (int i = 0; i < result.m_num_intervals; i++) {
+      float interval_duration_A = track_A.m_interval_ratio[i];
+      float interval_duration_B = track_B.m_interval_ratio[i];
+      result.m_interval_ratio[i] =
+          (1.0f - weight) * interval_duration_A + weight * interval_duration_B;
+
+      if (i < cSyncTrackMaxIntervals) {
+        result.m_interval_start[i + 1] =
+            result.m_interval_start[i] + result.m_interval_ratio[i];
+        if (result.m_interval_start[i + 1] > 1.0f) {
+          result.m_interval_start[i + 1] =
+              fmodf(result.m_interval_start[i + 1], 1.0f);
+        }
+
+        result.m_sync_markers[i + 1] = result.m_interval_start[i + 1];
+      }
+    }
+
+    assert (result.m_num_intervals < cSyncTrackMaxIntervals);
+
+    return result;
+  }
+
+  void DrawDebugUi();
+};
+
+#endif  //ANIMTESTBED_SYNCTRACK_H

src/main.cc

@@ -17,9 +17,10 @@
 #include "Camera.h"
 #include "SkinnedMesh.h"
 #include "GLFW/glfw3.h"
+#include "embedded_fonts.h"
 
-const int Width = 1024;
-const int Height = 768;
+const int Width = 2420;
+const int Height = 1480;
 const int MaxVertices = (1 << 16);
 const int MaxIndices = MaxVertices * 3;
 
@@ -199,16 +200,40 @@ int main() {
   SkinnedMesh skinned_mesh;
   skinned_mesh.LoadSkeleton("../media/MixamoYBot-skeleton.ozz");
   skinned_mesh.LoadAnimation("../media/Idle-loop.ozz");
+
+  int anim_idx = 0;
+  float idle_markers[] = {0.f, 0.5};
+  skinned_mesh.m_animation_sync_track[anim_idx] = SyncTrack::CreateFromMarkers(skinned_mesh.m_animations[anim_idx]->duration(), 2, idle_markers);
+
+  anim_idx = 1;
   skinned_mesh.LoadAnimation("../media/Walking-loop.ozz");
+  float walking_markers[] = {0.293, 0.762};
+  skinned_mesh.m_animation_sync_track[anim_idx] = SyncTrack::CreateFromMarkers(skinned_mesh.m_animations[anim_idx]->duration(), 2, walking_markers);
+
+  anim_idx = 2;
   skinned_mesh.LoadAnimation("../media/RunningSlow-loop.ozz");
+  float running_slow_markers[] = {0.315, 0.834};
+  skinned_mesh.m_animation_sync_track[anim_idx] = SyncTrack::CreateFromMarkers(skinned_mesh.m_animations[anim_idx]->duration(), 2, running_slow_markers);
+
+  anim_idx = 3;
   skinned_mesh.LoadAnimation("../media/RunningFast-loop.ozz");
+  float running_fast_markers[] = {0.403, 0.818};
+  skinned_mesh.m_animation_sync_track[anim_idx] = SyncTrack::CreateFromMarkers(skinned_mesh.m_animations[anim_idx]->duration(), 2, running_fast_markers);
+
+  anim_idx = 4;
   skinned_mesh.LoadAnimation("../media/Limping-loop.ozz");
+  float limping_markers[] = {0.757, 0.044};
+  skinned_mesh.m_animation_sync_track[anim_idx] = SyncTrack::CreateFromMarkers(skinned_mesh.m_animations[anim_idx]->duration(), 2, limping_markers);
+
+  anim_idx = 5;
   skinned_mesh.LoadAnimation("../media/ZombieWalk-loop.ozz");
+  float zombiewalk_markers[] = {0.619, 0.};
+  skinned_mesh.m_animation_sync_track[anim_idx] = SyncTrack::CreateFromMarkers(skinned_mesh.m_animations[anim_idx]->duration(), 2, zombiewalk_markers);
+
   skinned_mesh.SetCurrentAnimation(0);
 
   AnimationController animation_controller (&skinned_mesh);
 
-//  state.ozz = std::make_unique<ozz_t>();
   state.time.factor = 1.0f;
 
   Camera_Init(&state.camera);
@@ -217,8 +242,24 @@ int main() {
   ImGui::CreateContext();
   ImGui::StyleColorsDark();
   ImGuiIO& io = ImGui::GetIO();
-  io.IniFilename = nullptr;
-  io.Fonts->AddFontDefault();
+  io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;
+  io.IniFilename = "ATPImgui.ini";
+
+  ImGui::GetStyle().ScaleAllSizes(2.0);
+
+  //io.Fonts->AddFontDefault();
+  ImFontConfig font_config;
+  font_config.OversampleH = 4;
+  font_config.OversampleV = 4;
+  font_config.GlyphExtraSpacing.x = 1.0f;
+  io.Fonts->AddFontFromMemoryCompressedTTF(
+      //      roboto_medium_ttf_compressed_data,
+      //      roboto_medium_ttf_compressed_size,
+      droid_sans_ttf_compressed_data,
+      droid_sans_ttf_compressed_size,
+      28,
+      &font_config);
+
   io.KeyMap[ImGuiKey_Tab] = GLFW_KEY_TAB;
   io.KeyMap[ImGuiKey_LeftArrow] = GLFW_KEY_LEFT;
   io.KeyMap[ImGuiKey_RightArrow] = GLFW_KEY_RIGHT;
@@ -408,11 +449,16 @@ int main() {
 
 
     draw_grid();
+    ImGui::SetNextWindowPos(ImVec2 (600, 60), ImGuiCond_FirstUseEver);
+    ImGui::SetNextWindowSize(ImVec2 (300, 400), ImGuiCond_FirstUseEver);
     skinned_mesh.DrawDebugUi();
     animation_controller.DrawDebugUi();
 
+    if (!skinned_mesh.m_sync_track_override) {
       animation_controller.UpdateTime(state.time.frame);
       animation_controller.Evaluate();
+    }
+    skinned_mesh.CalcModelMatrices();
 
     sgl_defaults();
     sgl_matrix_mode_projection();

tests/SyncTrackTests.cc

@@ -2,44 +2,201 @@
 // Created by martin on 16.11.21.
 //
 
+#include "SyncTrack.h"
 #include "catch.hpp"
 
-#include "SkinnedMesh.h"
-
-TEST_CASE("SyncTrackBlendSimple", "[SyncTrackBlend]") {
+TEST_CASE("Basic", "[SyncTrack]") {
   SyncTrack track_A;
   track_A.m_num_intervals = 2;
-  track_A.m_duration = 1.0;
-  track_A.m_interval_durations[0] = 0.8;
-  track_A.m_interval_durations[1] = 0.2;
+  track_A.m_duration = 2.0;
+  track_A.m_interval_start[0] = 0.f;
+  track_A.m_interval_ratio[0] = 0.7;
+  track_A.m_interval_start[1] = 0.7f;
+  track_A.m_interval_ratio[1] = 0.3;
 
   SyncTrack track_B;
   track_B.m_num_intervals = 2;
-  track_B.m_duration = 2.0;
-  track_B.m_interval_durations[0] = 0.1;
-  track_B.m_interval_durations[1] = 0.9;
+  track_B.m_duration = 1.5;
+  track_B.m_interval_start[0] = 0.0f;
+  track_B.m_interval_ratio[0] = 0.6;
+  track_B.m_interval_start[1] = 0.6f;
+  track_B.m_interval_ratio[1] = 0.4;
+
+  WHEN("Calculating sync time of track_B at 0.5 duration") {
+    float sync_time_at_0_75 =
+        track_B.CalcSyncFromAbsTime(0.5 * track_B.m_duration);
+    REQUIRE(sync_time_at_0_75 == Catch::Detail::Approx(0.83333));
+  }
+
+  WHEN("Calculating sync time of track_B at 0.6 duration") {
+    float sync_time_at_0_6 =
+        track_B.CalcSyncFromAbsTime(0.6 * track_B.m_duration);
+    REQUIRE(sync_time_at_0_6 == Catch::Detail::Approx(1.0));
+  }
+
+  WHEN("Calculating sync time of track_B at 0.7 duration") {
+    float sync_time_at_0_7 =
+        track_B.CalcSyncFromAbsTime(0.7 * track_B.m_duration);
+    REQUIRE(sync_time_at_0_7 == Catch::Detail::Approx(1.25));
+  }
+
+  WHEN("Calculating sync time of track_B at 0.0 duration") {
+    float sync_time_at_1_0 =
+        track_B.CalcSyncFromAbsTime(0.0 * track_B.m_duration);
+    REQUIRE(sync_time_at_1_0 == Catch::Detail::Approx(0.0));
+  }
+
+  WHEN("Calculating sync time of track_B at 1.0 duration") {
+    float sync_time_at_1_0 =
+        track_B.CalcSyncFromAbsTime(0.9999 * track_B.m_duration);
+    REQUIRE(sync_time_at_1_0 == Catch::Detail::Approx(2.0).epsilon(0.001f));
+  }
+
+  WHEN("Calculating ratio from sync time on track_A at 0.83333") {
+    float ratio = track_A.CalcRatioFromSyncTime(0.83333333);
+    REQUIRE(ratio == Catch::Detail::Approx(0.5833333));
+  }
+
+  WHEN("Calculating ratio from sync time on track_A at 0.83333") {
+    float ratio = track_A.CalcRatioFromSyncTime(1.25);
+    REQUIRE(ratio == Catch::Detail::Approx(0.775));
+  }
 
   WHEN("Blending two synctracks with weight 0.") {
     SyncTrack blended = SyncTrack::Blend(0.f, track_A, track_B);
 
-    THEN ("Result must equal track_A") {
-      REQUIRE(blended.m_duration == track_A.m_duration);
-      REQUIRE(
-          blended.m_interval_durations[0] == track_A.m_interval_durations[0]);
-      REQUIRE(
-          blended.m_interval_durations[1] == track_A.m_interval_durations[1]);
-    }
+    THEN("Result must equal track_A") { REQUIRE(track_A == blended); }
   }
 
   WHEN("Blending two synctracks with weight 1.") {
     SyncTrack blended = SyncTrack::Blend(1.f, track_A, track_B);
 
-    THEN ("Result must equal track_B") {
-      REQUIRE(blended.m_duration == track_B.m_duration);
+    THEN("Result must equal track_B") { REQUIRE(track_B == blended); }
+  }
+}
+
+TEST_CASE("Sync Marker Interval Calculation", "[SyncTrack]") {
+  SyncTrack track_A;
+  track_A.m_num_intervals = 2;
+  track_A.m_duration = 2.0;
+  track_A.m_sync_markers[0] = 0.9;
+  track_A.m_sync_markers[1] = 0.2;
+
+  WHEN("Calculating intervals") {
+    track_A.CalcIntervals();
+
+    CHECK(track_A.m_interval_start[0] == Catch::Detail::Approx(0.9f));
+    CHECK(track_A.m_interval_ratio[0] == Catch::Detail::Approx(0.3f));
+
+    CHECK(track_A.m_interval_start[1] == Catch::Detail::Approx(0.2f));
+    CHECK(track_A.m_interval_ratio[1] == Catch::Detail::Approx(0.7f));
+
+    WHEN("Querying ratio at sync time at 1.001") {
+      float ratio = track_A.CalcRatioFromSyncTime(1.0001f);
+      CHECK(ratio == Catch::Detail::Approx(0.2).epsilon(0.001));
+    }
+
+    WHEN("Querying ratio at sync time at 1.001") {
+      float ratio = track_A.CalcRatioFromSyncTime(0.0001f);
+      CHECK(ratio == Catch::Detail::Approx(0.9).epsilon(0.001));
+    }
+
+    WHEN("Querying ratio at sync time at 1.9999") {
+      float ratio = track_A.CalcRatioFromSyncTime(0.9999f);
+      CHECK(ratio == Catch::Detail::Approx(0.2).epsilon(0.001));
+    }
+  }
+
+  WHEN("Blending sync track with 3 events") {
+    track_A.m_num_intervals = 3;
+    track_A.m_duration = 2.0;
+    track_A.m_sync_markers[0] = 0.;
+    track_A.m_sync_markers[1] = 0.3;
+    track_A.m_sync_markers[2] = 0.9;
+    track_A.CalcIntervals();
+
+    SyncTrack track_B;
+    track_B.m_num_intervals = 3;
+    track_B.m_duration = 1.5;
+    track_B.m_sync_markers[0] = 0.7;
+    track_B.m_sync_markers[1] = 0.9;
+    track_B.m_sync_markers[2] = 0.2;
+    track_B.CalcIntervals();
+
+    WHEN("Calculating A's durations") {
+      CHECK(track_A.m_interval_ratio[0] == Catch::Detail::Approx(0.3));
+      CHECK(track_A.m_interval_ratio[1] == Catch::Detail::Approx(0.6));
+      CHECK(track_A.m_interval_ratio[2] == Catch::Detail::Approx(0.1));
+    }
+
+    WHEN("Calculating B's durations") {
+      CHECK(track_B.m_interval_ratio[0] == Catch::Detail::Approx(0.2));
+      CHECK(track_B.m_interval_ratio[1] == Catch::Detail::Approx(0.3));
+      CHECK(track_B.m_interval_ratio[2] == Catch::Detail::Approx(0.5));
+    }
+
+    WHEN("Blending two synctracks with weight 0.") {
+      SyncTrack blended = SyncTrack::Blend(0.f, track_A, track_B);
+
+      THEN("Result must equal track_A") { REQUIRE(track_A == blended); }
+    }
+
+    WHEN("Blending two synctracks with weight 1.") {
+      SyncTrack blended = SyncTrack::Blend(1.f, track_A, track_B);
+
+      THEN("Result must equal track_B") { REQUIRE(track_B == blended); }
+    }
+
+    WHEN("Blending with weight 0.2") {
+      float weight = 0.2f;
+      SyncTrack blended = SyncTrack::Blend(weight, track_A, track_B);
+
       REQUIRE(
-          blended.m_interval_durations[0] == track_B.m_interval_durations[0]);
+          blended.m_duration
+          == (1.0f - weight) * track_A.m_duration
+                 + weight * track_B.m_duration);
       REQUIRE(
-          blended.m_interval_durations[1] == track_B.m_interval_durations[1]);
+          blended.m_interval_start[0]
+          == fmodf(
+              (1.0f - weight) * (track_A.m_interval_start[0] + 1.0f)
+                  + weight * (track_B.m_interval_start[0]),
+              1.0f));
+      REQUIRE(
+          blended.m_interval_ratio[1]
+          == (1.0f - weight) * (track_A.m_interval_ratio[1])
+                  + weight * (track_B.m_interval_ratio[1])
+              );
+      REQUIRE(
+          blended.m_interval_ratio[2]
+          == (1.0f - weight) * (track_A.m_interval_ratio[2])
+                 + weight * (track_B.m_interval_ratio[2])
+      );
+    }
+
+    WHEN("Inverted blending with weight 0.2") {
+      float weight = 0.2f;
+      SyncTrack blended = SyncTrack::Blend(weight, track_B, track_A);
+
+      REQUIRE(
+          blended.m_duration
+          == (1.0f - weight) * track_B.m_duration
+                 + weight * track_A.m_duration);
+      REQUIRE(
+          blended.m_interval_start[0]
+          == fmodf(
+              (1.0f - weight) * (track_B.m_interval_start[0])
+                  + weight * (track_A.m_interval_start[0] + 1.0f),
+              1.0f));
+      REQUIRE(
+          blended.m_interval_ratio[1]
+          == (1.0f - weight) * (track_B.m_interval_ratio[1])
+                 + weight * (track_A.m_interval_ratio[1])
+      );
+      REQUIRE(
+          blended.m_interval_ratio[2]
+          == (1.0f - weight) * (track_B.m_interval_ratio[2])
+                 + weight * (track_A.m_interval_ratio[2])
+      );
     }
   }
 }