Avatar collision sounds.

collisionsSoundURL can be set in preferences:
  Currently defaults to https://s3.amazonaws.com/hifi-public/sounds/Collisions-hitsandslaps/airhockey_hit1.wav.
  Can be empty, which means no sound, rather than restoring default.
MyAvatar.collisionSoundURL can read/written in scripts.
Preloads when set, so that it won't have to fetch on first collision.
Plays at start of collision only, with volume proportional to "velocity change"^2.

interface/src/Application.cpp

@@ -2202,6 +2202,7 @@ void Application::init() {
 
     // Make sure any new sounds are loaded as soon as know about them.
     connect(tree, &EntityTree::newCollisionSoundURL, DependencyManager::get<SoundCache>().data(), &SoundCache::getSound);
+    connect(_myAvatar, &MyAvatar::newCollisionSoundURL, DependencyManager::get<SoundCache>().data(), &SoundCache::getSound);
 }
 
 void Application::closeMirrorView() {

interface/src/avatar/AvatarManager.cpp

@@ -257,6 +257,31 @@ void AvatarManager::handleOutgoingChanges(VectorOfMotionStates& motionStates) {
 
 void AvatarManager::handleCollisionEvents(CollisionEvents& collisionEvents) {
     // TODO: expose avatar collision events to JS
+    for (Collision collision : collisionEvents) {
+        if (collision.idA.isNull() || collision.idB.isNull()) {
+            MyAvatar* myAvatar = getMyAvatar();
+            const QString& collisionSoundURL = myAvatar->getCollisionSoundURL();
+            if (!collisionSoundURL.isEmpty()) {
+                const float velocityChange = glm::length(collision.velocityChange);
+                const float MIN_AVATAR_COLLISION_ACCELERATION = 0.01;
+                const bool isSound = (collision.type == CONTACT_EVENT_TYPE_START) && (velocityChange > MIN_AVATAR_COLLISION_ACCELERATION);
+
+                if (!isSound) {
+                    break;
+                }
+                // Your avatar sound is personal to you, so let's say the "mass" part of the kinetic energy is already accounted for.
+                const float energy = velocityChange * velocityChange;
+                const float COLLISION_ENERGY_AT_FULL_VOLUME = 0.5f;
+                const float energyFactorOfFull = fmin(1.0f, energy / COLLISION_ENERGY_AT_FULL_VOLUME);
+
+                // For general entity collisionSoundURL, playSound supports changing the pitch for the sound based on the size of the object,
+                // but most avatars are roughly the same size, so let's not be so fancy yet.
+                const float AVATAR_STRETCH_FACTOR = 1.0f;
+
+                AudioInjector::playSound(collisionSoundURL, energyFactorOfFull, AVATAR_STRETCH_FACTOR, myAvatar->getPosition());
+            }
+        }
+    }
 }
 
 void AvatarManager::updateAvatarPhysicsShape(const QUuid& id) {

interface/src/avatar/MyAvatar.cpp

@@ -70,6 +70,7 @@ float DEFAULT_SCRIPTED_MOTOR_TIMESCALE = 1.0e6f;
 const int SCRIPTED_MOTOR_CAMERA_FRAME = 0;
 const int SCRIPTED_MOTOR_AVATAR_FRAME = 1;
 const int SCRIPTED_MOTOR_WORLD_FRAME = 2;
+const QString& DEFAULT_AVATAR_COLLISION_SOUND_URL = "https://s3.amazonaws.com/hifi-public/sounds/Collisions-hitsandslaps/airhockey_hit1.wav";
 
 const float MyAvatar::ZOOM_MIN = 0.5f;
 const float MyAvatar::ZOOM_MAX = 10.0f;
@@ -90,6 +91,7 @@ MyAvatar::MyAvatar() :
     _scriptedMotorTimescale(DEFAULT_SCRIPTED_MOTOR_TIMESCALE),
     _scriptedMotorFrame(SCRIPTED_MOTOR_CAMERA_FRAME),
     _motionBehaviors(AVATAR_MOTION_DEFAULTS),
+    _collisionSoundURL(""),
     _characterController(this),
     _lookAtTargetAvatar(),
     _shouldRender(true),
@@ -664,6 +666,7 @@ void MyAvatar::saveData() {
     settings.endArray();
 
     settings.setValue("displayName", _displayName);
+    settings.setValue("collisionSoundURL", _collisionSoundURL);
 
     settings.endGroup();
 }
@@ -789,6 +792,7 @@ void MyAvatar::loadData() {
     settings.endArray();
 
     setDisplayName(settings.value("displayName").toString());
+    setCollisionSoundURL(settings.value("collisionSoundURL", DEFAULT_AVATAR_COLLISION_SOUND_URL).toString());
 
     settings.endGroup();
 }
@@ -1183,6 +1187,13 @@ void MyAvatar::clearScriptableSettings() {
     _scriptedMotorTimescale = DEFAULT_SCRIPTED_MOTOR_TIMESCALE;
 }
 
+void MyAvatar::setCollisionSoundURL(const QString& url) {
+    if (!url.isEmpty() && (url != _collisionSoundURL)) {
+        emit newCollisionSoundURL(QUrl(url));
+    }
+    _collisionSoundURL = url;
+}
+
 void MyAvatar::attach(const QString& modelURL, const QString& jointName, const glm::vec3& translation,
         const glm::quat& rotation, float scale, bool allowDuplicates, bool useSaved) {
     if (QThread::currentThread() != thread()) {

interface/src/avatar/MyAvatar.h

@@ -25,6 +25,7 @@ class MyAvatar : public Avatar {
     Q_PROPERTY(glm::vec3 motorVelocity READ getScriptedMotorVelocity WRITE setScriptedMotorVelocity)
     Q_PROPERTY(float motorTimescale READ getScriptedMotorTimescale WRITE setScriptedMotorTimescale)
     Q_PROPERTY(QString motorReferenceFrame READ getScriptedMotorFrame WRITE setScriptedMotorFrame)
+    Q_PROPERTY(QString collisionSoundURL READ getCollisionSoundURL WRITE setCollisionSoundURL)
     //TODO: make gravity feature work Q_PROPERTY(glm::vec3 gravity READ getGravity WRITE setGravity)
 
 public:
@@ -150,6 +151,9 @@ public:
     void setScriptedMotorTimescale(float timescale);
     void setScriptedMotorFrame(QString frame);
 
+    const QString& getCollisionSoundURL() {return _collisionSoundURL; }
+    void setCollisionSoundURL(const QString& url);
+
     void clearScriptableSettings();
 
     virtual void attach(const QString& modelURL, const QString& jointName = QString(),
@@ -204,6 +208,7 @@ public slots:
     
 signals:
     void transformChanged();
+    void newCollisionSoundURL(const QUrl& url);
 
 private:
 
@@ -233,6 +238,7 @@ private:
     float _scriptedMotorTimescale; // timescale for avatar to achieve its target velocity
     int _scriptedMotorFrame;
     quint32 _motionBehaviors;
+    QString _collisionSoundURL;
 
     DynamicCharacterController _characterController;
 

interface/src/ui/PreferencesDialog.cpp

@@ -127,6 +127,8 @@ void PreferencesDialog::loadPreferences() {
     _displayNameString = myAvatar->getDisplayName();
     ui.displayNameEdit->setText(_displayNameString);
 
+    ui.collisionSoundURLEdit->setText(myAvatar->getCollisionSoundURL());
+
     ui.sendDataCheckBox->setChecked(!menuInstance->isOptionChecked(MenuOption::DisableActivityLogger));
 
     ui.snapshotLocationEdit->setText(Snapshot::snapshotsLocation.get());
@@ -204,6 +206,8 @@ void PreferencesDialog::savePreferences() {
         myAvatar->sendIdentityPacket();
     }
     
+    myAvatar->setCollisionSoundURL(ui.collisionSoundURLEdit->text());
+
     if (!Menu::getInstance()->isOptionChecked(MenuOption::DisableActivityLogger)
         != ui.sendDataCheckBox->isChecked()) {
         Menu::getInstance()->triggerOption(MenuOption::DisableActivityLogger);

interface/ui/preferencesDialog.ui

@@ -189,6 +189,66 @@
          </item>
         </layout>
        </item>
+
+       <item>
+        <layout class="QVBoxLayout" name="verticalLayout_5csu">
+         <property name="spacing">
+          <number>0</number>
+         </property>
+         <property name="topMargin">
+          <number>7</number>
+         </property>
+         <property name="bottomMargin">
+          <number>7</number>
+         </property>
+         <item>
+          <widget class="QLabel" name="avatarCollisionSoundURLLabel">
+           <property name="font">
+            <font>
+             <family>Arial</family>
+            </font>
+           </property>
+           <property name="text">
+            <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Avatar collision sound URL &lt;span style=&quot; color:#909090;&quot;&gt;(optional)&lt;/span&gt;&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
+           </property>
+           <property name="alignment">
+            <set>Qt::AlignBottom|Qt::AlignLeading|Qt::AlignLeft</set>
+           </property>
+           <property name="buddy">
+            <cstring>collisionSoundURLEdit</cstring>
+           </property>
+          </widget>
+         </item>
+         <item>
+          <layout class="QHBoxLayout" name="horizontalLayout_17csu">
+           <property name="topMargin">
+            <number>4</number>
+           </property>
+           <property name="rightMargin">
+            <number>5</number>
+           </property>
+           <property name="bottomMargin">
+            <number>4</number>
+           </property>
+           <item>
+            <widget class="QLineEdit" name="collisionSoundURLEdit">
+             <property name="font">
+              <font>
+               <family>Arial</family>
+              </font>
+             </property>
+             <property name="layoutDirection">
+              <enum>Qt::LeftToRight</enum>
+             </property>
+             <property name="placeholderText">
+              <string>Enter the URL of a sound to play when you bump into something</string>
+             </property>
+            </widget>
+           </item>
+          </layout>
+         </item>
+        </layout>
+       </item>
        
        <item>
         <layout class="QVBoxLayout" name="verticalLayout_appearance">