From 97bcc543605eb343d7d71c47545a3c05a14dcd9c Mon Sep 17 00:00:00 2001
From: "Anthony J. Thibault" <tony@highfidelity.io>
Date: Mon, 8 Feb 2016 16:01:36 -0800
Subject: [PATCH] CharacterController: separate target velocity from parent
 velocity.

Also, disable damping on the rigidBody used by the CharacterController.
---
 examples/moving-platform.js                   | 41 +++++++++++++++++++
 interface/src/avatar/MyAvatar.cpp             |  3 +-
 .../src/avatar/MyCharacterController.cpp      |  1 +
 libraries/physics/src/CharacterController.cpp | 15 ++++---
 libraries/physics/src/CharacterController.h   |  4 +-
 5 files changed, 56 insertions(+), 8 deletions(-)
 create mode 100644 examples/moving-platform.js

diff --git a/examples/moving-platform.js b/examples/moving-platform.js
new file mode 100644
index 0000000000..94e45bb571
--- /dev/null
+++ b/examples/moving-platform.js
@@ -0,0 +1,41 @@
+var platform;
+
+function init() {
+    platform = Entities.addEntity({
+        name: "platform",
+        type: "Box",
+        position: { x: 0, y: 0, z: 0 },
+        dimensions: { x: 10, y: 2, z: 10 },
+        color: { red: 0, green: 0, blue: 255 },
+        gravity: { x: 0, y: 0, z: 0 },
+        visible: true,
+        locked: false,
+        lifetime: 6000,
+        velocity: { x: 1.0, y: 0, z: 0 },
+        damping: 0,
+        isDynamic: false
+    });
+    if (platform) {
+        MyAvatar.position = { x: 0, y: 3, z: 0 };
+        if (MyAvatar.getParentID() != platform) {
+            MyAvatar.setParentID(platform);
+        }
+    }
+}
+
+function update(dt) {
+
+}
+
+function shutdown() {
+    if (platform) {
+        MyAvatar.setParentID(0);
+        Entities.deleteEntity(platform);
+    }
+}
+
+
+init();
+
+Script.update.connect(update);
+Script.scriptEnding.connect(shutdown);
diff --git a/interface/src/avatar/MyAvatar.cpp b/interface/src/avatar/MyAvatar.cpp
index c7b415ba09..1436c192b5 100644
--- a/interface/src/avatar/MyAvatar.cpp
+++ b/interface/src/avatar/MyAvatar.cpp
@@ -1089,7 +1089,8 @@ void MyAvatar::prepareForPhysicsSimulation() {
         }
     }
 
-    _characterController.setTargetVelocity(getTargetVelocity() + parentVelocity);
+    _characterController.setParentVelocity(parentVelocity);
+    _characterController.setTargetVelocity(getTargetVelocity());
     _characterController.setPositionAndOrientation(getPosition(), getOrientation());
     if (qApp->isHMDMode()) {
         _follow.prePhysicsUpdate(*this, deriveBodyFromHMDSensor(), _bodySensorMatrix);
diff --git a/interface/src/avatar/MyCharacterController.cpp b/interface/src/avatar/MyCharacterController.cpp
index 07156e9294..ee77859337 100644
--- a/interface/src/avatar/MyCharacterController.cpp
+++ b/interface/src/avatar/MyCharacterController.cpp
@@ -67,6 +67,7 @@ void MyCharacterController::updateShapeIfNecessary() {
             _rigidBody->setAngularFactor(0.0f);
             _rigidBody->setWorldTransform(btTransform(glmToBullet(_avatar->getOrientation()),
                                                       glmToBullet(_avatar->getPosition())));
+            _rigidBody->setDamping(0.0f, 0.0f);
             if (_state == State::Hover) {
                 _rigidBody->setGravity(btVector3(0.0f, 0.0f, 0.0f));
             } else {
diff --git a/libraries/physics/src/CharacterController.cpp b/libraries/physics/src/CharacterController.cpp
index 1f61bb9a59..9dd40a35a7 100644
--- a/libraries/physics/src/CharacterController.cpp
+++ b/libraries/physics/src/CharacterController.cpp
@@ -54,7 +54,7 @@ CharacterController::CharacterController() {
 
     _floorDistance = MAX_FALL_HEIGHT;
 
-    _walkVelocity.setValue(0.0f, 0.0f, 0.0f);
+    _targetVelocity.setValue(0.0f, 0.0f, 0.0f);
     _followDesiredBodyTransform.setIdentity();
     _followTimeRemaining = 0.0f;
     _jumpSpeed = JUMP_SPEED;
@@ -166,12 +166,12 @@ void CharacterController::playerStep(btCollisionWorld* dynaWorld, btScalar dt) {
 
     const btScalar MIN_SPEED = 0.001f;
 
-    btVector3 actualVelocity = _rigidBody->getLinearVelocity();
+    btVector3 actualVelocity = _rigidBody->getLinearVelocity() - _parentVelocity;
     if (actualVelocity.length() < MIN_SPEED) {
         actualVelocity = btVector3(0.0f, 0.0f, 0.0f);
     }
 
-    btVector3 desiredVelocity = _walkVelocity;
+    btVector3 desiredVelocity = _targetVelocity;
     if (desiredVelocity.length() < MIN_SPEED) {
         desiredVelocity = btVector3(0.0f, 0.0f, 0.0f);
     }
@@ -212,7 +212,7 @@ void CharacterController::playerStep(btCollisionWorld* dynaWorld, btScalar dt) {
         break;
     }
 
-    _rigidBody->setLinearVelocity(finalVelocity);
+    _rigidBody->setLinearVelocity(finalVelocity + _parentVelocity);
 
     // Dynamicaly compute a follow velocity to move this body toward the _followDesiredBodyTransform.
     // Rather then add this velocity to velocity the RigidBody, we explicitly teleport the RigidBody towards its goal.
@@ -383,8 +383,11 @@ void CharacterController::getPositionAndOrientation(glm::vec3& position, glm::qu
 }
 
 void CharacterController::setTargetVelocity(const glm::vec3& velocity) {
-    //_walkVelocity = glmToBullet(_avatarData->getTargetVelocity());
-    _walkVelocity = glmToBullet(velocity);
+    _targetVelocity = glmToBullet(velocity);
+}
+
+void CharacterController::setParentVelocity(const glm::vec3& velocity) {
+    _parentVelocity = glmToBullet(velocity);
 }
 
 void CharacterController::setFollowParameters(const glm::mat4& desiredWorldBodyMatrix, float timeRemaining) {
diff --git a/libraries/physics/src/CharacterController.h b/libraries/physics/src/CharacterController.h
index 86ef350812..5362ca52e4 100644
--- a/libraries/physics/src/CharacterController.h
+++ b/libraries/physics/src/CharacterController.h
@@ -69,6 +69,7 @@ public:
     void getPositionAndOrientation(glm::vec3& position, glm::quat& rotation) const;
 
     void setTargetVelocity(const glm::vec3& velocity);
+    void setParentVelocity(const glm::vec3& parentVelocity);
     void setFollowParameters(const glm::mat4& desiredWorldMatrix, float timeRemaining);
     float getFollowTime() const { return _followTime; }
     glm::vec3 getFollowLinearDisplacement() const;
@@ -105,7 +106,8 @@ protected:
 
 protected:
     btVector3 _currentUp;
-    btVector3 _walkVelocity;
+    btVector3 _targetVelocity;
+    btVector3 _parentVelocity;
     btTransform _followDesiredBodyTransform;
     btScalar _followTimeRemaining;
     btTransform _characterBodyTransform;