1 files changed, 72 insertions, 0 deletions
diff --git a/indra/llcommon/llcriticaldamp.cpp b/indra/llcommon/llcriticaldamp.cpp
new file mode 100644
index 0000000000..ee7dfecdaa
--- /dev/null
+++ b/indra/llcommon/llcriticaldamp.cpp
@@ -0,0 +1,72 @@
+/** 
+ * @file llcriticaldamp.cpp
+ * @brief Implementation of the critical damping functionality.
+ *
+ * Copyright (c) 2002-$CurrentYear$, Linden Research, Inc.
+ * $License$
+ */
+
+#include "linden_common.h"
+#include <math.h>
+
+#include "llcriticaldamp.h"
+
+//-----------------------------------------------------------------------------
+// static members
+//-----------------------------------------------------------------------------
+LLFrameTimer LLCriticalDamp::sInternalTimer;
+std::map<F32, F32> LLCriticalDamp::sInterpolants;
+F32 LLCriticalDamp::sTimeDelta;
+
+//-----------------------------------------------------------------------------
+// LLCriticalDamp()
+//-----------------------------------------------------------------------------
+LLCriticalDamp::LLCriticalDamp()
+{
+	sTimeDelta = 0.f;
+}
+
+// static
+//-----------------------------------------------------------------------------
+// updateInterpolants()
+//-----------------------------------------------------------------------------
+void LLCriticalDamp::updateInterpolants()
+{
+	sTimeDelta = sInternalTimer.getElapsedTimeAndResetF32();
+
+	F32 time_constant;
+
+	for (std::map<F32, F32>::iterator iter = sInterpolants.begin();
+		 iter != sInterpolants.end(); iter++)
+	{
+		time_constant = iter->first;
+		F32 new_interpolant = 1.f - pow(2.f, -sTimeDelta / time_constant);
+		new_interpolant = llclamp(new_interpolant, 0.f, 1.f);
+		sInterpolants[time_constant] = new_interpolant;
+	}
+} 
+
+//-----------------------------------------------------------------------------
+// getInterpolant()
+//-----------------------------------------------------------------------------
+F32 LLCriticalDamp::getInterpolant(const F32 time_constant, BOOL use_cache)
+{
+	if (time_constant == 0.f)
+	{
+		return 1.f;
+	}
+
+	if (use_cache && sInterpolants.count(time_constant))
+	{
+		return sInterpolants[time_constant];
+	}
+	
+	F32 interpolant = 1.f - pow(2.f, -sTimeDelta / time_constant);
+	interpolant = llclamp(interpolant, 0.f, 1.f);
+	if (use_cache)
+	{
+		sInterpolants[time_constant] = interpolant;
+	}
+
+	return interpolant;
+}