Make sure we do not recompute automatically center of mass and inertia tensor when they are set by the user

src/body/RigidBody.cpp

@@ -42,7 +42,7 @@ RigidBody::RigidBody(const Transform& transform, CollisionWorld& world, bodyinde
           : CollisionBody(transform, world, id), mArrayIndex(0), mInitMass(decimal(1.0)),
             mCenterOfMassLocal(0, 0, 0), mCenterOfMassWorld(transform.getPosition()),
             mIsGravityEnabled(true), mLinearDamping(decimal(0.0)), mAngularDamping(decimal(0.0)),
-            mJointsList(nullptr) {
+            mJointsList(nullptr), mIsCenterOfMassSetByUser(false), mIsInertiaTensorSetByUser(false) {
 
     // Compute the inverse mass
     mMassInverse = decimal(1.0) / mInitMass;
@@ -93,15 +93,17 @@ void RigidBody::setType(BodyType type) {
         mMassInverse = decimal(0.0);
         mInertiaTensorLocalInverse.setToZero();
         mInertiaTensorInverseWorld.setToZero();
-
     }
     else {  // If it is a dynamic body
         mMassInverse = decimal(1.0) / mInitMass;
+
+        if (mIsInertiaTensorSetByUser) {
             mInertiaTensorLocalInverse = mUserInertiaTensorLocalInverse;
+        }
+    }
 
     // Update the world inverse inertia tensor
     updateInertiaTensorInverseWorld();
-    }
 
     // Awake the body
     setIsSleeping(false);
@@ -119,6 +121,8 @@ void RigidBody::setType(BodyType type) {
 }
 
 // Set the local inertia tensor of the body (in local-space coordinates)
+/// If the inertia tensor is set with this method, it will not be computed
+/// using the collision shapes of the body.
 /**
  * @param inertiaTensorLocal The 3x3 inertia tensor matrix of the body in local-space
  *                           coordinates
@@ -126,6 +130,7 @@ void RigidBody::setType(BodyType type) {
 void RigidBody::setInertiaTensorLocal(const Matrix3x3& inertiaTensorLocal) {
 
     mUserInertiaTensorLocalInverse = inertiaTensorLocal.getInverse();
+    mIsInertiaTensorSetByUser = true;
 
     if (mType != BodyType::DYNAMIC) return;
 
@@ -136,10 +141,17 @@ void RigidBody::setInertiaTensorLocal(const Matrix3x3& inertiaTensorLocal) {
     updateInertiaTensorInverseWorld();
 }
 
-// Set the inverse local inertia tensor of the body (in body coordinates)
+// Set the inverse local inertia tensor of the body (in local-space coordinates)
+/// If the inverse inertia tensor is set with this method, it will not be computed
+/// using the collision shapes of the body.
+/**
+ * @param inverseInertiaTensorLocal The 3x3 inverse inertia tensor matrix of the body in local-space
+ *                           		coordinates
+ */
 void RigidBody::setInverseInertiaTensorLocal(const Matrix3x3& inverseInertiaTensorLocal) {
 
     mUserInertiaTensorLocalInverse = inverseInertiaTensorLocal;
+    mIsInertiaTensorSetByUser = true;
 
     if (mType != BodyType::DYNAMIC) return;
 
@@ -151,6 +163,8 @@ void RigidBody::setInverseInertiaTensorLocal(const Matrix3x3& inverseInertiaTens
 }
 
 // Set the local center of mass of the body (in local-space coordinates)
+/// If you set the center of mass with the method, it will not be computed
+/// automatically using collision shapes.
 /**
  * @param centerOfMassLocal The center of mass of the body in local-space
  *                          coordinates
@@ -159,6 +173,8 @@ void RigidBody::setCenterOfMassLocal(const Vector3& centerOfMassLocal) {
 
     if (mType != BodyType::DYNAMIC) return;
 
+    mIsCenterOfMassSetByUser = true;
+
     const Vector3 oldCenterOfMass = mCenterOfMassWorld;
     mCenterOfMassLocal = centerOfMassLocal;
 
@@ -359,9 +375,9 @@ void RigidBody::recomputeMassInformation() {
 
     mInitMass = decimal(0.0);
     mMassInverse = decimal(0.0);
-    mInertiaTensorLocalInverse.setToZero();
-    mInertiaTensorInverseWorld.setToZero();
-    mCenterOfMassLocal.setToZero();
+    if (!mIsInertiaTensorSetByUser) mInertiaTensorLocalInverse.setToZero();
+    if (!mIsInertiaTensorSetByUser) mInertiaTensorInverseWorld.setToZero();
+    if (!mIsCenterOfMassSetByUser) mCenterOfMassLocal.setToZero();
     Matrix3x3 inertiaTensorLocal;
     inertiaTensorLocal.setToZero();
 
@@ -376,8 +392,11 @@ void RigidBody::recomputeMassInformation() {
     // Compute the total mass of the body
     for (ProxyShape* shape = mProxyCollisionShapes; shape != nullptr; shape = shape->mNext) {
         mInitMass += shape->getMass();
+
+        if (!mIsCenterOfMassSetByUser) {
             mCenterOfMassLocal += shape->getLocalToBodyTransform().getPosition() * shape->getMass();
         }
+    }
 
     if (mInitMass > decimal(0.0)) {
         mMassInverse = decimal(1.0) / mInitMass;
@@ -389,10 +408,16 @@ void RigidBody::recomputeMassInformation() {
 
     // Compute the center of mass
     const Vector3 oldCenterOfMass = mCenterOfMassWorld;
+
+    if (!mIsCenterOfMassSetByUser) {
         mCenterOfMassLocal *= mMassInverse;
+    }
+
     mCenterOfMassWorld = mTransform * mCenterOfMassLocal;
 
-    // Compute the total mass and inertia tensor using all the collision shapes
+    if (!mIsInertiaTensorSetByUser) {
+
+        // Compute the inertia tensor using all the collision shapes
         for (ProxyShape* shape = mProxyCollisionShapes; shape != nullptr; shape = shape->mNext) {
 
             // Get the inertia tensor of the collision shape in its local-space
@@ -422,6 +447,7 @@ void RigidBody::recomputeMassInformation() {
 
         // Compute the local inverse inertia tensor
         mInertiaTensorLocalInverse = inertiaTensorLocal.getInverse();
+    }
 
     // Update the world inverse inertia tensor
     updateInertiaTensorInverseWorld();

src/body/RigidBody.h

@@ -109,6 +109,12 @@ class RigidBody : public CollisionBody {
         /// First element of the linked list of joints involving this body
         JointListElement* mJointsList;
 
+        /// True if the center of mass is set by the user
+        bool mIsCenterOfMassSetByUser;
+
+        /// True if the inertia tensor is set by the user
+        bool mIsInertiaTensorSetByUser;
+
         // -------------------- Methods -------------------- //
 
         /// Remove a joint from the joints list