Implemented sync track blending for tracks with more than 2 markers.

src/SkinnedMesh.h

@@ -27,8 +27,7 @@ struct SyncTrack {
   int m_num_intervals;
   float m_sync_markers[cSyncTrackMaxIntervals];
   float m_interval_start[cSyncTrackMaxIntervals];
-  float m_interval_end[cSyncTrackMaxIntervals];
-  float m_interval_durations[cSyncTrackMaxIntervals];
+  float m_interval_ratio[cSyncTrackMaxIntervals];
 
   void CalcIntervals() {
     int i;
@@ -36,20 +35,21 @@ struct SyncTrack {
     if (m_num_intervals == 0) {
       m_num_intervals = 1;
       m_interval_start[0] = 0.f;
-      m_interval_end[0] = 1.f;
+      m_interval_ratio[0] = 1.f;
     } else {
       for (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];
-        m_interval_end[i] = m_sync_markers[end_index];
+        float interval_end = m_sync_markers[end_index];
 
-        if (m_interval_end[i] > m_interval_start[i]) {
-          m_interval_durations[i] = m_interval_end[i] - m_interval_start[i];
-        } else {
-          m_interval_durations[i] =
-              m_interval_end[i] + (1. - m_interval_start[i]);
+        if (interval_end < m_interval_start[i]) {
+          interval_end += 1.0f;
         }
+
+        m_interval_ratio[i] = interval_end - m_interval_start[i];
       }
     }
   }
@@ -58,13 +58,12 @@ struct SyncTrack {
     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];
+    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_durations[interval_index];
+    return float(interval_index) + sync_time / m_interval_ratio[interval_index];
   }
 
   float CalcRatioFromSyncTime(float sync_time) {
@@ -73,10 +72,29 @@ struct SyncTrack {
 
     return fmodf(
         m_interval_start[interval]
-            + m_interval_durations[interval] * interval_ratio,
+            + 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
   Blend(float weight, const SyncTrack& track_A, const SyncTrack& track_B) {
     assert(track_A.m_num_intervals == track_B.m_num_intervals);
@@ -87,22 +105,34 @@ struct SyncTrack {
     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++) {
-      result.m_interval_durations[i] =
-          (1.0f - weight) * track_A.m_interval_durations[i]
-          + weight * track_B.m_interval_durations[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;
 
-      result.m_interval_start[i] =
-          (1.0f - weight) * track_A.m_interval_start[i]
-          + weight * track_B.m_interval_start[i];
-
-      result.m_interval_end[i] =
-          (1.0f - weight) * track_A.m_interval_end[i]
-          + weight * track_B.m_interval_end[i];
-
-      result.m_sync_markers[i] =
-          (1.0f - weight) * track_A.m_sync_markers[i]
-          + weight * track_B.m_sync_markers[i];
+      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);
+        }
+      }
     }
 
     return result;