From c033f08d04f417e4b29907bf95e72b35cffc8854 Mon Sep 17 00:00:00 2001
From: Bert Peters <bert@bertptrs.nl>
Date: Tue, 13 Feb 2018 11:09:04 +0100
Subject: [PATCH] Compute a fractional animation step for every frame.

This step is used to interpolate animations.
---
 src/main.cpp  |  2 ++
 src/utils.hpp | 20 ++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/src/main.cpp b/src/main.cpp
index 75a50d9..ae15114 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -26,6 +26,7 @@ struct
     vector<vector<LayerData>>::iterator currentData;
     vector<unique_ptr<LayerVisualisation>> layerVisualisations;
     vector<unique_ptr<ActivityAnimation>> animations;
+    float animationStep = 0;
 } rendererData;
 
 static void loadSimulationData(const Options &options)
@@ -153,6 +154,7 @@ static void idleFunc()
     checkGLErrors();
     glutPostRedisplay();
     throttleIdleFunc();
+    rendererData.animationStep = getAnimationStep(std::chrono::seconds(5));
 }
 
 int main(int argc, char *argv[])
diff --git a/src/utils.hpp b/src/utils.hpp
index 4eea72d..dd5964e 100644
--- a/src/utils.hpp
+++ b/src/utils.hpp
@@ -9,6 +9,8 @@
 #include <string>
 #include <utility>
 #include <vector>
+#include <ratio>
+#include <chrono>
 
 namespace fmri
 {
@@ -155,4 +157,22 @@ namespace fmri
      */
     std::default_random_engine& rng();
 
+    /**
+     *
+     * @tparam Duration Duration type of length
+     * @param length
+     * @return
+     */
+    template<class Duration>
+    float getAnimationStep(const Duration &length) {
+        using namespace std::chrono;
+
+        static auto startingPoint = steady_clock::now();
+        const auto modified_length = duration_cast<steady_clock::duration>(length);
+
+        auto step = (steady_clock::now() - startingPoint) % modified_length;
+
+        return static_cast<float>(step.count()) / static_cast<float>(modified_length.count());
+    }
+
 }