From 073cec41c41c77546824f2fda5780c8a28c86df5 Mon Sep 17 00:00:00 2001
From: "Anthony J. Thibault" <tony@highfidelity.io>
Date: Fri, 16 Oct 2015 12:11:46 -0700
Subject: [PATCH] AnimClip & accumulateTime smoother looping anims

Looping animations should have an extra frame of interpolation between the start and end frames.
---
 libraries/animation/src/AnimClip.cpp | 11 ++++++-----
 libraries/animation/src/AnimUtil.cpp |  7 +++++--
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/libraries/animation/src/AnimClip.cpp b/libraries/animation/src/AnimClip.cpp
index 97f46a1b68..613194164f 100644
--- a/libraries/animation/src/AnimClip.cpp
+++ b/libraries/animation/src/AnimClip.cpp
@@ -47,16 +47,17 @@ const AnimPoseVec& AnimClip::evaluate(const AnimVariantMap& animVars, float dt,
     }
 
     if (_anim.size()) {
-        int frameCount = _anim.size();
-
         int prevIndex = (int)glm::floor(_frame);
-        int nextIndex = (int)glm::ceil(_frame);
-        if (_loopFlag && nextIndex >= frameCount) {
-            nextIndex = 0;
+        int nextIndex;
+        if (_loopFlag && _frame >= _endFrame) {
+            nextIndex = (int)glm::ceil(_startFrame);
+        } else {
+            nextIndex = (int)glm::ceil(_frame);
         }
 
         // It can be quite possible for the user to set _startFrame and _endFrame to
         // values before or past valid ranges.  We clamp the frames here.
+        int frameCount = _anim.size();
         prevIndex = std::min(std::max(0, prevIndex), frameCount - 1);
         nextIndex = std::min(std::max(0, nextIndex), frameCount - 1);
 
diff --git a/libraries/animation/src/AnimUtil.cpp b/libraries/animation/src/AnimUtil.cpp
index c8efa85df9..e9e5ea95de 100644
--- a/libraries/animation/src/AnimUtil.cpp
+++ b/libraries/animation/src/AnimUtil.cpp
@@ -29,8 +29,7 @@ float accumulateTime(float startFrame, float endFrame, float timeScale, float cu
 
     float frame = currentFrame;
     const float clampedStartFrame = std::min(startFrame, endFrame);
-    if (clampedStartFrame == endFrame) {
-        // when clampedStartFrame >= endFrame
+    if (fabsf(clampedStartFrame - endFrame) < 1.0f) {
         frame = endFrame;
     } else if (timeScale > 0.0f) {
         // accumulate time, keeping track of loops and end of animation events.
@@ -38,6 +37,10 @@ float accumulateTime(float startFrame, float endFrame, float timeScale, float cu
         float framesRemaining = (dt * timeScale) * FRAMES_PER_SECOND;
         while (framesRemaining > 0.0f) {
             float framesTillEnd = endFrame - frame;
+            // when looping, add one frame between start and end.
+            if (loopFlag) {
+                framesTillEnd += 1.0f;
+            }
             if (framesRemaining >= framesTillEnd) {
                 if (loopFlag) {
                     // anim loop