Rotate a vector about any arbitrary axis

#1 The object is actually being rotated normally (and as you desire), however, the networking code makes that assumption I alluded to in the public forums post: items should only rotate about their Z axis.

Note the following code from item.cc, roughly line 802:

U32 Item::packUpdate(NetConnection *connection, U32 mask, BitStream *stream)
{
   U32 retMask = Parent::packUpdate(connection,mask,stream);

   if (stream->writeFlag(mask & InitialUpdateMask)) {
      stream->writeFlag(mRotate);
      stream->writeFlag(mStatic);
      stream->writeFlag(mCollideable);
      if (stream->writeFlag(getScale() != Point3F(1, 1, 1)))
         mathWrite(*stream, getScale());
   }
   if (mask & ThrowSrcMask && mCollisionObject) {
      S32 gIndex = connection->getGhostIndex(mCollisionObject);
      if (stream->writeFlag(gIndex != -1))
         stream->writeInt(gIndex,NetConnection::GhostIdBitSize);
   }
   else
      stream->writeFlag(false);
   if (stream->writeFlag(mask & RotationMask && !mRotate)) {
      // Assumes rotation is about the Z axis
      AngAxisF aa(mObjToWorld);
      stream->writeFlag(aa.axis.z < 0);
      stream->write(aa.angle);
   }
   if (stream->writeFlag(mask & PositionMask)) {
      Point3F pos;
      mObjToWorld.getColumn(3,&pos);
      mathWrite(*stream, pos);
      if (!stream->writeFlag(mAtRest)) {
         mathWrite(*stream, mVelocity);
      }
      stream->writeFlag(!(mask & NoWarpMask));
   }
   return retMask;
}

Specifically, the following block:

...
   if (stream->writeFlag(mask & RotationMask && !mRotate)) {
      // Assumes rotation is about the Z axis
      AngAxisF aa(mObjToWorld);
      stream->writeFlag(aa.axis.z < 0);
      stream->write(aa.angle);
   }
...

As you can see, it only ever sends the Z axis rotation (aa.axis.z < 0, and aa.angle), and the corresponding unpackUpdate() (just after in the file) only affects the z axis based on the BitStream sent.

If you want all 3 dimensions of rotation, you should modify your Item class to use the same technique as is used in the Vehicle::packUpdate() and Vehicle::unpackUpdate() in vehicle.cc.

Alternatively, you could derive your class from Vehicle, and that portion would be done for you already (although you'd pick up a lot of things most likely that you don't need).

#2 Thx, will look at it...:)

#3 Again, used this, it works the way it should but theres a problem with this...i am adding a ball as an Item, and whenever it moves some distance, the ball starts switching places, it keeps switching between two places, i guess for some reason the client and server synch is getting messed up, because of which the problem occurs, any ideas and fixes for the same...

also the Item::settransform() function modified it too, so that the axis related stuf is removed. this is my current code...


U32 Item::packUpdate(NetConnection *connection, U32 mask, BitStream *stream)
{
U32 retMask = Parent::packUpdate(connection,mask,stream);
if (stream->writeFlag(mask & InitialUpdateMask))
{
stream->writeFlag(mRotate);
stream->writeFlag(mStatic);
stream->writeFlag(mCollideable);
stream->writeFlag( mGenerateShadow );
if (stream->writeFlag(getScale() != Point3F(1, 1, 1)))
mathWrite(*stream, getScale());
}
if (mask & ThrowSrcMask && mCollisionObject)
{
S32 gIndex = connection->getGhostIndex(mCollisionObject);
if (stream->writeFlag(gIndex != -1))
stream->writeInt(gIndex,NetConnection::GhostIdBitSize);
}
else
stream->writeFlag(false);
if (stream->writeFlag(mask & PositionMask))
{
stream->writeAffineTransform(mObjToWorld);
mathWrite(*stream, mObjScale);
//Point3F pos;
//mObjToWorld.getColumn(3,&pos);
//mathWrite(*stream, pos);
if (!stream->writeFlag(mAtRest))
{
mathWrite(*stream, mVelocity);
}
stream->writeFlag(!(mask & NoWarpMask));
}
return retMask;
}

void Item::unpackUpdate(NetConnection *connection, BitStream *stream)
{
Parent::unpackUpdate(connection,stream);
if (stream->readFlag())
{
mRotate = stream->readFlag();
mStatic = stream->readFlag();
mCollideable = stream->readFlag();
mGenerateShadow = stream->readFlag();
if (stream->readFlag())
mathRead(*stream, &mObjScale);
else
mObjScale.set(1, 1, 1);
}
if (stream->readFlag())
{
S32 gIndex = stream->readInt(10);
setCollisionTimeout(static_cast(connection->resolveGhost(gIndex)));
}
if (stream->readFlag())
{
// From StaticShape
MatrixF mat;
stream->readAffineTransform(&mat);
VectorF scale;
mathRead(*stream, &scale);
setScale(scale); // Original Code
Point3F pos;
mat.getColumn(3,&pos);
F32 speed = mVelocity.len();
if ((mAtRest = stream->readFlag()) == true)
mVelocity.set(0,0,0);
else
mathRead(*stream, &mVelocity);
if (stream->readFlag() && isProperlyAdded())
{
// Determine number of ticks to warp based on the average
// of the client and server velocities.
delta.warpOffset = pos - delta.pos;
F32 as = (speed + mVelocity.len()) * 0.5 * TickSec;
F32 dt = (as > 0.00001f) ? delta.warpOffset.len() / as: sMaxWarpTicks;
delta.warpTicks = (S32)((dt > sMinWarpTicks)? getMax(mFloor(dt + 0.5), 1.0f): 0.0f);
if (delta.warpTicks)
{
// Setup the warp to start on the next tick, only the
// object's position is warped.
if (delta.warpTicks > sMaxWarpTicks)
delta.warpTicks = sMaxWarpTicks;
delta.warpOffset /= delta.warpTicks;
}
else
{
// Going to skip the warp, server and client are real close.
// Adjust the frame interpolation to move smoothly to the
// new position within the current tick.
Point3F cp = delta.pos + delta.posVec * delta.dt;
VectorF vec = delta.pos - cp;
F32 vl = vec.len();
if (vl)
{
F32 s = delta.posVec.len() / vl;
delta.posVec = (cp - pos) * s;
}
delta.pos = pos;
mat.setColumn(3,pos);
}
}
else
{
// Set the item to the server position
delta.warpTicks = 0;
delta.posVec.set(0,0,0);
delta.pos = pos;
delta.dt = 0;
mat.setColumn(3,pos);
}
Parent::setTransform(mat);
Parent::setRenderTransform(mat);
}
}


void Item::setTransform(const MatrixF& mat)
{
Parent::setTransform(mat);
setMaskBits(PositionMask | NoWarpMask);
}


i got this in one of the forums.


Thx,
Ravi.