Smooth, configurable rotation for AIPlayers

Here's the code I usually use to give AIPlayers smooth yaw:
As a bonus, you also get an AIPlayerData namespace for your AI scripting.

*** NOTE ***
For all engine builds up to and including T3D 1.1final, there is a bug in the player interpolation and networking code that affects the rotation of AIPlayers. The bug is discussed here, and you will need to apply Ivan's fixes for this resource to work correctly.


Now, lets hack away at the engine:

in AIPlayer.h
before:

class AIPlayer : public Player {

add:

class AIPlayerData : public PlayerData {
   typedef PlayerData Parent;

public:
   AIPlayerData(); // CTor

   // maximum yaw rate
   F32 maxTurnRate;
   
   // standard datablock stuff
   DECLARE_CONOBJECT(AIPlayerData);
   static void initPersistFields();
   virtual void packData(BitStream* stream);
   virtual void unpackData(BitStream* stream);
};

then in AIPlayer.cpp
before

IMPLEMENT_CO_NETOBJECT_V1(AIPlayer);

add

#include "core/stream/bitStream.h"

// AIPlayerData datablock functions
IMPLEMENT_CO_DATABLOCK_V1(AIPlayerData);

AIPlayerData::AIPlayerData()
{
   maxTurnRate = M_2PI_F; // default to 1 full circle per second
}

void AIPlayerData::initPersistFields()
{
   Parent::initPersistFields();
   addField("maxTurnRate",    TypeF32, Offset(maxTurnRate,     AIPlayerData));
}

void AIPlayerData::packData(BitStream* stream)
{
   Parent::packData(stream);
   stream->write(maxTurnRate);
} 

void AIPlayerData::unpackData(BitStream* stream)
{
   Parent::unpackData(stream);
   stream->read(&maxTurnRate);
}

now we need to make the AIPlayer class actually use the AIPlayerData datablock
in AIPlayer.h,
after

typedef Player Parent

add

AIPlayerData *mDataBlock;        // our new datablock type

still in AIPlayer.h,
after

~AIPlayer();

add

bool onNewDataBlock(GameBaseData* dptr, bool reload);  // new datablock assigned

then in AIPlayer.cpp,
in the AIPlayer constructor, after

mAimOffset = Point3F(0.0f, 0.0f, 0.0f);

add

mDataBlock = 0;

then at the end of AIPlayer.cpp, add the function to handle the new datablock assignment

bool AIPlayer::onNewDataBlock(GameBaseData* dptr, bool reload)
{
   mDataBlock = dynamic_cast<AIPlayerData*>(dptr);
   if (!mDataBlock || !Parent::onNewDataBlock(dptr, reload))
      return false;
   
   scriptOnNewDataBlock();
   return true;
}

Then, the code that actually controls the rate of turn
in AIPlayer.cpp, in the getAIMove function, replace

movePtr->yaw = yawDiff;

with

// control the rotation of the AIPlayer
   
         // get the maximum amount we can yaw this tick
         F32 maxYaw = mDataBlock->maxTurnRate * TickSec;

         // limit the yaw if it exceeds the maxYaw
         if(mFabs(yawDiff) > maxYaw)
            movePtr->yaw = maxYaw * mSign(yawDiff);
         else
            movePtr->yaw = yawDiff;

Finally, in script, you need to change the datablocks that your AIPlayers use from PlayerData to AIPlayerData - e.g.
find

datablock PlayerData(DemoPlayer : DefaultPlayerData)

and change it to

datablock AIPlayerData(DemoPlayer : DefaultPlayerData)

and then add a line for maxTurnRate to the datablock.
Don't use very small values for the maxTurnRate, as the networking compresses rotation and positions, so you will get artifacts for too small values. Some useful values are:
maxTurnRate = 6.3; // approx 360 degrees per second
maxTurnRate = 3.15 // approx 180 degrees per second
maxTurnRate = 1.6 // approx 90 degrees per second

*Edit* - simplified to use mSign as Daniel suggests