A lot of FPS agnosticism, added def lerp

Data/Scripts/001_Technical/002_RubyUtilities.rb

@@ -389,3 +389,14 @@ end
 def nil_or_empty?(string)
   return string.nil? || !string.is_a?(String) || string.size == 0
 end
+
+# Linear interpolation between two values, given the duration of the change and
+# either:
+#   - the time passed since the start of the change (delta), or
+#   - the start time of the change (delta) and the current time (now)
+def lerp(start_val, end_val, duration, delta, now = nil)
+  delta = now - delta if now
+  return start_val if delta <= 0
+  return end_val if delta >= duration
+  return start_val + (end_val - start_val) * delta / duration
+end