Camera is now using animate2 but isn't actually using it yet. Just converted.

ease2.cpp

@@ -12,6 +12,10 @@ namespace ease2 {
     return 0.0;
   }
 
+  double linear(float tick) {
+    return tick;
+  }
+
   double sine(double x) {
     // old one? return std::abs(std::sin(seq.subframe * ease_rate));
     return (std::sin(x) + 1.0) / 2.0;
@@ -107,6 +111,7 @@ namespace ease2 {
     {"random", random},
     {"normal_dist", normal_dist},
     {"none", none},
+    {"linear", linear},
   };
 
   std::unordered_map<std::string, MotionFunc> map_of_motions{