Add friction feature to motion tab

#344

src/res/qml/motion_page/gravity/GravityGroupBox.qml

@@ -113,6 +113,43 @@ GroupBox {
                 }
             }
 
+            Item {
+                Layout.preferredWidth: 40
+            }
+
+            MyText {
+                text: "Friction:"
+                horizontalAlignment: Text.AlignRight
+                Layout.rightMargin: 2
+            }
+
+            MyTextField {
+                id: frictionPercentText
+                text: "0%"
+                keyBoardUID: 156
+                Layout.preferredWidth: 130
+                Layout.leftMargin: 5
+                horizontalAlignment: Text.AlignHCenter
+                function onInputEvent(input) {
+                    var val = parseInt(input)
+                    if (!isNaN(val)) {
+                        if ( val > 999 )
+                        {
+                            val = 999
+                        }
+                        if ( val < 0 )
+                        {
+                            val = 0
+                        }
+
+                        MoveCenterTabController.frictionPercent = val
+                        text = MoveCenterTabController.frictionPercent + "%"
+                    } else {
+                        text = MoveCenterTabController.frictionPercent + "%"
+                    }
+                }
+            }
+
             Item {
                 Layout.fillWidth: true
             }
@@ -166,14 +203,6 @@ GroupBox {
                 }
             }
 
-            MyPushButton2 {
-                Layout.preferredWidth: 50
-                text: "4x"
-                onClicked: {
-                    MoveCenterTabController.flingStrength = 4.0
-                }
-            }
-
 
         }
     }
@@ -183,6 +212,7 @@ GroupBox {
         gravityStrengthText.text = MoveCenterTabController.gravityStrength.toFixed(2)
         momentumToggleButton.checked = MoveCenterTabController.momentumSave
         flingStrengthText.text = MoveCenterTabController.flingStrength.toFixed(2)
+        frictionPercentText.text = MoveCenterTabController.frictionPercent + "%"
     }
 
     Connections {
@@ -200,5 +230,8 @@ GroupBox {
         onFlingStrengthChanged: {
             flingStrengthText.text = MoveCenterTabController.flingStrength.toFixed(2)
         }
+        onFrictionPercentChanged: {
+            frictionPercentText.text = MoveCenterTabController.frictionPercent + "%"
+        }
     }
 }

src/settings/internal/settings_controller.h

@@ -455,6 +455,10 @@ private:
                          SettingCategory::Playspace,
                          QtInfo{ "turnComfortFactor" },
                          0 },
+        IntSettingValue{ IntSetting::PLAYSPACE_frictionPercent,
+                         SettingCategory::Playspace,
+                         QtInfo{ "frictionPercent" },
+                         0 },
 
         IntSettingValue{ IntSetting::APPLICATION_debugState,
                          SettingCategory::Application,

src/settings/settings.h

@@ -90,6 +90,7 @@ enum class IntSetting
     PLAYSPACE_smoothTurnRate,
     PLAYSPACE_dragComfortFactor,
     PLAYSPACE_turnComfortFactor,
+    PLAYSPACE_frictionPercent,
 
     APPLICATION_debugState,
     APPLICATION_customTickRateMs,

src/tabcontrollers/MoveCenterTabController.cpp

@@ -464,6 +464,12 @@ int MoveCenterTabController::smoothTurnRate() const
         settings::IntSetting::PLAYSPACE_smoothTurnRate );
 }
 
+int MoveCenterTabController::frictionPercent() const
+{
+    return settings::getSetting(
+        settings::IntSetting::PLAYSPACE_frictionPercent );
+}
+
 void MoveCenterTabController::setSmoothTurnRate( int value, bool notify )
 {
     settings::setSetting( settings::IntSetting::PLAYSPACE_smoothTurnRate,
@@ -475,6 +481,17 @@ void MoveCenterTabController::setSmoothTurnRate( int value, bool notify )
     }
 }
 
+void MoveCenterTabController::setFrictionPercent( int value, bool notify )
+{
+    settings::setSetting( settings::IntSetting::PLAYSPACE_frictionPercent,
+                          value );
+
+    if ( notify )
+    {
+        emit frictionPercentChanged( value );
+    }
+}
+
 bool MoveCenterTabController::adjustChaperone() const
 {
     return settings::getSetting(
@@ -1929,12 +1946,6 @@ void MoveCenterTabController::gravityToggleAction(
 
 void MoveCenterTabController::gravityReverseAction( bool gravityReverseHeld )
 {
-    // detect new press or new release
-    if ( ( gravityReverseHeld && !m_gravityReversed )
-         || ( !gravityReverseHeld && m_gravityReversed ) )
-    {
-        setGravityStrength( gravityStrength() * -1.0f );
-    }
     m_gravityReversed = gravityReverseHeld;
 }
 
@@ -2374,6 +2385,50 @@ void MoveCenterTabController::updateHandTurn(
 
 void MoveCenterTabController::updateGravity()
 {
+    float currentGravity = gravityStrength();
+    if ( m_gravityReversed )
+    {
+        currentGravity *= -1.0f;
+    }
+    double secondsSinceLastGravityUpdate
+        = std::chrono::duration<double>( std::chrono::steady_clock::now()
+                                         - m_lastGravityUpdateTimePoint )
+              .count();
+
+    // apply friction
+    if ( frictionPercent() > 0 )
+    {
+        // if we have friction and all velocity components are less than
+        // halt speed, we stop.
+        if ( abs( m_velocity[0] ) < k_frictionHalt_mps
+             && abs( m_velocity[1] ) < k_frictionHalt_mps
+             && abs( m_velocity[2] ) < k_frictionHalt_mps )
+        {
+            m_velocity[0] = 0.0;
+            m_velocity[1] = 0.0;
+            m_velocity[2] = 0.0;
+        }
+        else
+        {
+            // frictionPercent() * 10 is scaler such that at 90fps we
+            // reduce from terminal velocity (50m/s) to about 1mm/s in 1
+            // second using 100% friction. This is an arbitrary scaler,
+            // but doing a more accurate job would require a performance
+            // hit of the math pow() function to an arbitrary exponent.
+            double frictionVelocityMultiplier
+                = ( 100.0
+                    - ( static_cast<double>( frictionPercent() * 10 )
+                        * secondsSinceLastGravityUpdate ) )
+                  / 100.0;
+            frictionVelocityMultiplier
+                = std::clamp( frictionVelocityMultiplier, 0.0, 1.0 );
+
+            m_velocity[0] *= frictionVelocityMultiplier;
+            m_velocity[1] *= frictionVelocityMultiplier;
+            m_velocity[2] *= frictionVelocityMultiplier;
+        }
+    }
+
     // prevent velocity underflow
     if ( std::isnan( m_velocity[0] ) )
     {
@@ -2405,23 +2460,18 @@ void MoveCenterTabController::updateGravity()
         m_velocity[2] = 0.0;
     }
 
-    double secondsSinceLastGravityUpdate
-        = std::chrono::duration<double>( std::chrono::steady_clock::now()
-                                         - m_lastGravityUpdateTimePoint )
-              .count();
-
     // are we falling?
     // note: up is negative y
-    // note: set to always fall if gravity reversed (strength < 0)
+    // note: set to always fall if gravity reversed (currentGravity < 0)
-    if ( ( m_offsetY < m_gravityFloor ) || ( gravityStrength() < 0 ) )
+    if ( ( m_offsetY < m_gravityFloor ) || ( currentGravity < 0 ) )
     {
         // check if we're about to land
-        // note: we don't land if gravity is reversed (strength < 0)
+        // note: we don't land if gravity is reversed (currentGravity < 0)
         if ( ( m_offsetY
                    + static_cast<float>( m_velocity[1]
                                          * secondsSinceLastGravityUpdate )
                >= m_gravityFloor )
-             && gravityStrength() >= 0 )
+             && currentGravity >= 0 )
         {
             // get ratio of how much from y velocity applied to overcome y
             // offset and get down to ground.
@@ -2462,7 +2512,7 @@ void MoveCenterTabController::updateGravity()
             // accelerate downward velocity for the next update
             // note: downward is positive y
             m_velocity[1] = m_velocity[1]
-                            + ( static_cast<double>( gravityStrength() )
+                            + ( static_cast<double>( currentGravity )
                                 * secondsSinceLastGravityUpdate );
             return;
         }

src/tabcontrollers/MoveCenterTabController.h

@@ -17,6 +17,9 @@ constexpr double k_radiansToCentidegrees = 18000.0 / M_PI;
 constexpr double k_quaternionInvalidValue = -1000.0;
 constexpr double k_quaternionUnderIsInvalidValueThreshold = -900.0;
 constexpr double k_terminalVelocity_mps = 50.0;
+// k_frictionHalt_mps must be sufficiently small to allow a single tick of
+// gravity through
+constexpr double k_frictionHalt_mps = 0.0000001;
 // give the max offset a buffer to avoid crossing when traveling at astronomical
 // velocities
 constexpr double k_maxOpenvrWorkingSetOffest = 39900.0;
@@ -53,6 +56,8 @@ class MoveCenterTabController : public QObject
                     NOTIFY snapTurnAngleChanged )
     Q_PROPERTY( int smoothTurnRate READ smoothTurnRate WRITE setSmoothTurnRate
                     NOTIFY smoothTurnRateChanged )
+    Q_PROPERTY( int frictionPercent READ frictionPercent WRITE
+                    setFrictionPercent NOTIFY frictionPercentChanged )
     Q_PROPERTY( bool adjustChaperone READ adjustChaperone WRITE
                     setAdjustChaperone NOTIFY adjustChaperoneChanged )
     Q_PROPERTY( bool moveShortcutRight READ moveShortcutRight WRITE
@@ -214,6 +219,7 @@ public:
     int tempRotation() const;
     int snapTurnAngle() const;
     int smoothTurnRate() const;
+    int frictionPercent() const;
     bool adjustChaperone() const;
     bool moveShortcutRight() const;
     bool moveShortcutLeft() const;
@@ -285,6 +291,7 @@ public slots:
     void setTempRotation( int value, bool notify = true );
     void setSnapTurnAngle( int value, bool notify = true );
     void setSmoothTurnRate( int value, bool notify = true );
+    void setFrictionPercent( int value, bool notify = true );
 
     void setAdjustChaperone( bool value, bool notify = true );
     void setMoveShortcutRight( bool value, bool notify = true );
@@ -336,6 +343,7 @@ signals:
     void tempRotationChanged( int value );
     void snapTurnAngleChanged( int value );
     void smoothTurnRateChanged( int value );
+    void frictionPercentChanged( int value );
     void adjustChaperoneChanged( bool value );
     void moveShortcutRightChanged( bool value );
     void moveShortcutLeftChanged( bool value );