Make panner's doppler rate continuous as the source position approaches the listener position.

Source/modules/webaudio/PannerNode.cpp

 /*
  * Copyright (C) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 367 matching lines @@
 }
 
 void PannerNode::calculateAzimuthElevation(double* outAzimuth, double* outElevation)
 {
     double azimuth = 0.0;
 
     // Calculate the source-listener vector
     FloatPoint3D listenerPosition = listener()->position();
     FloatPoint3D sourceListener = m_position - listenerPosition;
 
-    if (sourceListener.isZero()) {
-        // degenerate case if source and listener are at the same point
-        *outAzimuth = 0.0;
-        *outElevation = 0.0;
-        return;
-    }
-
+    // normalize() does nothing if the length of |sourceListener| is zero.
     sourceListener.normalize();
 
     // Align axes
     FloatPoint3D listenerFront = listener()->orientation();
     FloatPoint3D listenerUp = listener()->upVector();
     FloatPoint3D listenerRight = listenerFront.cross(listenerUp);
     listenerRight.normalize();
 
     FloatPoint3D listenerFrontNorm = listenerFront;
     listenerFrontNorm.normalize();
@@ skipping 49 matching lines @@
         bool sourceHasVelocity = !sourceVelocity.isZero();
         bool listenerHasVelocity = !listenerVelocity.isZero();
 
         if (sourceHasVelocity || listenerHasVelocity) {
             // Calculate the source to listener vector
             FloatPoint3D listenerPosition = listener()->position();
             FloatPoint3D sourceToListener = m_position - listenerPosition;
 
             double sourceListenerMagnitude = sourceToListener.length();
 
-            double listenerProjection = sourceToListener.dot(listenerVelocity) / sourceListenerMagnitude;
-            double sourceProjection = sourceToListener.dot(sourceVelocity) / sourceListenerMagnitude;
+            if (!sourceListenerMagnitude) {
+                // Source and listener are at the same position. Skip the computation of the doppler
+                // shift, and just return the cached value.
+                dopplerShift = m_cachedDopplerRate;
+            } else {
+                double listenerProjection = sourceToListener.dot(listenerVelocity) / sourceListenerMagnitude;
+                double sourceProjection = sourceToListener.dot(sourceVelocity) / sourceListenerMagnitude;
 
-            listenerProjection = -listenerProjection;
-            sourceProjection = -sourceProjection;
+                listenerProjection = -listenerProjection;
+                sourceProjection = -sourceProjection;
 
-            double scaledSpeedOfSound = speedOfSound / dopplerFactor;
-            listenerProjection = min(listenerProjection, scaledSpeedOfSound);
-            sourceProjection = min(sourceProjection, scaledSpeedOfSound);
+                double scaledSpeedOfSound = speedOfSound / dopplerFactor;
+                listenerProjection = min(listenerProjection, scaledSpeedOfSound);
+                sourceProjection = min(sourceProjection, scaledSpeedOfSound);
 
-            dopplerShift = ((speedOfSound - dopplerFactor * listenerProjection) / (speedOfSound - dopplerFactor * sourceProjection));
-            fixNANs(dopplerShift); // avoid illegal values
+                dopplerShift = ((speedOfSound - dopplerFactor * listenerProjection) / (speedOfSound - dopplerFactor * sourceProjection));
+                fixNANs(dopplerShift); // avoid illegal values
 
-            // Limit the pitch shifting to 4 octaves up and 3 octaves down.
-            if (dopplerShift > 16.0)
-                dopplerShift = 16.0;
-            else if (dopplerShift < 0.125)
-                dopplerShift = 0.125;
+                // Limit the pitch shifting to 4 octaves up and 3 octaves down.
+                if (dopplerShift > 16.0)
+                    dopplerShift = 16.0;
+                else if (dopplerShift < 0.125)
+                    dopplerShift = 0.125;
+            }
         }
     }
 
     return dopplerShift;
 }
 
 float PannerNode::calculateDistanceConeGain()
 {
     FloatPoint3D listenerPosition = listener()->position();
 
@@ skipping 81 matching lines @@
                     notifyAudioSourcesConnectedToNode(connectedNode, visitedNodes); // recurse
                 }
             }
         }
     }
 }
 
 } // namespace WebCore
 
 #endif // ENABLE(WEB_AUDIO)