Target Prediction

[aeo]

I'm working on a LUA extension for wow and I have most of it working. Id like to make some smarter hunter traps but am having some issues calculating the position to cast the trap based on target position and speed.

function predictPosition(x,y,z,vel,target)
local px = x
local py = y
local pz = z
local dist = GetUnitDistance(target);
if vel == 0 then
return px,py,pz
else
px = x + (vel * ( dist / 25)) --25 yards/sec is the trap travel time( roughly)
px = y + (vel * ( dist / 25)) --velocity is the Units speed usually 7.7 unmounted
px = z + (vel * ( dist / 25))
return px,py,pz
end

I've searched here and Google. Without much luck, maybe I'm using the wrong search terms. Hoping some expert can help me out

Thanks,
Ace

[Jadd]

You need the rotation vectors, to account for the direction they are running in, whether they are strafing left or right, or running forward or backwards. Doing "<x or y> + (vel * (dist / 25))" will only work assuming they are running directly east or south. In fact, that will be wrong too when the velocity is applied to both axes.

function PredictTrapPosition(x, y, z, rotation, velocity, distance, direction)
    local trapSpeed = distance / 25
    local trapDistance = trapSpeed * velocity
    local forward = 1
    local right = 0

    if (direction == 1) -- Running forward
        forward = 1
    elseif (direction == 2) -- Running backward
        forward = -1
    elseif (direction == 3) -- Strafing right
        right = 1
    elseif (direction == 4) -- Strafing left
        right = -1
    end

    x = x + ((trapDistance * cos(rotation + ((math.pi / 2) * right))) * forward)
    y = y + ((trapDistance * sin(rotation + ((math.pi / 2) * right))) * forward)
    
    return x, y, z
end

[aeo]

Amazing thanks, should be able to get it working from here. Thanks JADD,

I can get the rotation vectors, However, is the only way to retrieve the movement direction via the Unit movement flags?

Thanks,

[Jadd]

However, is the only way to retrieve the movement direction via the Unit movement flags?

Certainly not the only way, but the easiest. This information is not exposed to the WoW Lua API, if that's what you are looking for.

[aeo]

Yep i found an old post by you and have the movement struct and data working. I expose this information to LUA myself via newly registered functions. One last stupid question, CGObject_C::GetRotation and CGObject_C::GetFacing they seem to be all mixed up when people talk about them on the board facing is a float in radians and rotation is another vector or C4Quaternion acording to TOM_RUS vTable examples?

So i have it all working i get the correct values for direction 1,2,4,8 seems I only get them for my self and my pet. Others log as 2147483649

[Jadd]

Are you trying to find the object rotation, or whether they are moving forward/backward/strafing?

For object rotation use GetRotation. To find their movement direction, check their movement state flags in the CMovementData struct (forward = 1, backward = 2, strafe left = 4, strafe right = 8.)

[aeo]

II have the movement flags working at least for myself and my pet it seems othernunits don't get proper values. I have to look into get rotation I was using the facing float value.

Edit. I tried get rotation as a float but no luck. I can't find much info on the return type of getrotation . I'll try int64 tomorrow but clearly still have some learning to do.

[aeo]

I have yet to get consistent values for the movement flags. Doing research looking through old IDBs im pretty sure i have the right offsets.Yet I seem to get the wrong values. Originally I was using 0xA38 as the dataOffset but that seemed to only return valid numbers for my LocalPlayer and Pet. This is quickly starting to become quite the project. I was going to just PM you but I figured others can learn as well.

Below is some code that you wrote in another post. The offsets are for Live 19342

        DWORD UnitMovementData = 0x124;
    DWORD UnitMovementFlags = 0x40;


        
    /// <summary>
    /// Gets the unit's movement structure pointer.
    /// </summary>
    DWORD_PTR GetMovementData() const
    {
        Log("getData");
        Log("Data 0x%x", *(DWORD_PTR*)(this + UnitMovementData));
            return *(DWORD_PTR*)( this +
                UnitMovementData);
    }


    /// <summary>
    /// Gets the unit's movement flags.
    /// </summary>
    DWORD GetMovementFlags() const
    {
        Log("GetFlag");
        Log("Flag 0x%x", *(DWORD*)(this + UnitMovementFlags));
        return *(DWORD*)(GetMovementData() + UnitMovementFlags);
    }

Also as you can see the Script_IsFalling shows these offsets should be correct.

signed int __cdecl Script_IsFalling(int a1)
{
  int v1; // eax@2
  int v2; // eax@2
  int v3; // eax@5
  int v4; // eax@7


  if ( klua_isstring(a1, 1) )
  {
    v1 = klua_tolstring(a1, 1, 0);
    v2 = GetUnitFromName(v1);
  }
  else
  {
    v2 = ClntObjMgrGetActivePlayerObj();
  }
  v4 = 0;
  if ( v2 )
  {
    v3 = *(_DWORD *)(*(_DWORD *)(v2 + 0x124) + 0x40);
    if ( v3 & 0x800 )
    {
      if ( !(v3 & 0x400) )
        v4 = 1;
    }
  }
  klua_pushboolean(a1, v4);
  return 1;
}

[Jadd]

Take another look at your GetMovementFlags function. The return value should be right, but the logging...

[aeo]

Fail didn't get it properly output it to LUA either. Its working now. ! more question good sir.Rotation is that the actual Yaw pitch roll of the unit or the facing angle in radians? Everywhere i look for getRotation on this site its people referring to the Facing angle or the Float that is in the movement struct right after the Z value. Not that actual Yaw/Pitch/Roll values.

Also IDA defines it like this

int __userpurge CGObject_C::GetRotation@<eax>(int a1@<ecx>, double a2@<st0>, int a3)
Do you know what the last 2 args are?

Thanks for all your help, I really appreciate your patience.

Edit:

OK making a little progress. I switched from doing to computation on the LUA side to the C++ side. Seems to be working but hitting traps at the wrong side running forward it shots a bit left. I think my velocityVector is incorrect.

			int32 direction = (WoWMovementFlag)(unit->GetMovementFlags() & 0xFF);
			C3Vector velVec;
			if (direction == 1) // Running forward6
			{
				velVec = C3Vector(0, 7, 0);
			}
			else if (direction == 2)  // Running backward
			{
				velVec = C3Vector(0, -7, 0);
			}
			else if (direction == 4)  // Strafing right
			{
				velVec = C3Vector(7, 0, 0);
			}
			else if (direction == 8) // Strafing left
			{
				velVec = C3Vector(-7, 0, 0);
			}
			C3Vector me;
			ObjectMgr::getlocalPlayer()->GetPosition(me);
			aimPos = FindInterceptVector(me, 25, pos, velVec);

C3Vector FindInterceptVector(C3Vector shotOrigin, float shotSpeed,
	C3Vector targetOrigin, C3Vector targetVel) {


	C3Vector dirToTarget = targetOrigin - shotOrigin;
	dirToTarget.normaliZeVector3D();


	// Decompose the target's velocity into the part parallel to the
	// direction to the cannon and the part tangential to it.
	// The part towards the cannon is found by projecting the target's
	// velocity on dirToTarget using a dot product.
	C3Vector targetVelOrth = targetVel.dotVector3D(dirToTarget) * dirToTarget;


	// The tangential part is then found by subtracting the
	// result from the target velocity.
	C3Vector targetVelTang = targetVel - targetVelOrth;


	/*
	* targetVelOrth
	* |
	* |
	*
	* ^...7  <-targetVel
	* |  /.
	* | / .
	* |/ .
	* t--->  <-targetVelTang
	*
	*
	* s--->  <-shotVelTang
	*
	*/


	// The tangential component of the velocities should be the same
	// (or there is no chance to hit)
	// THIS IS THE MAIN INSIGHT!
	C3Vector shotVelTang = targetVelTang;


	// Now all we have to find is the orthogonal velocity of the shot


	float shotVelSpeed = shotVelTang.GetMagnitude();
	if (shotVelSpeed > shotSpeed) {
		// Shot is too slow to intercept target, it will never catch up.
		// Do our best by aiming in the direction of the targets velocity.
		targetVel.normaliZeVector3D();
		return  targetVel * shotSpeed;
	}
	else {
		// We know the shot speed, and the tangential velocity.
		// Using pythagoras we can find the orthogonal velocity.
		float shotSpeedOrth =
			sqrt(shotSpeed * shotSpeed - shotVelSpeed * shotVelSpeed);
		C3Vector shotVelOrth = dirToTarget * shotSpeedOrth;


		// Finally, add the tangential and orthogonal velocities.
		// Find the time of collision (distance / relative velocity)
		float timeToCollision = ((shotOrigin - targetOrigin).GetMagnitude())
			/ (shotVelOrth.GetMagnitude() - targetVelOrth.GetMagnitude());


		// Calculate where the shot will be at the time of collision
		C3Vector shotVel = shotVelOrth + shotVelTang;
		C3Vector shotCollisionPoint = shotOrigin + shotVel * timeToCollision;
		return shotCollisionPoint;


	}
}

[Jadd]

Everywhere i look for getRotation on this site its people referring to the Facing angle or the Float that is in the movement struct right after the Z value. Not that actual Yaw/Pitch/Roll values.

The value you refer to is yaw (rotation on the X and Y axes.) Pitch is only used when flying or swimming. Roll is not used for obvious reasons.

int __userpurge CGObject_C::GetRotation@<eax>(int a1@<ecx>, double a2@<st0>, int a3)
Do you know what the last 2 args are?

This is a small error on the behalf of IDA - it has no reference calls to base the parameter interpretation from, as it is a virtual method. It's a __thiscall and takes a float as the first and only parameter. No idea what this float does. You might want to see what it is via. breakpoint.

I'll check your code out a bit later tonight.

[Wildbreath]

you can do it using lua. just use timer and get first + second vector of target and calculate result using trap speed and velocity player and target. but you should use intersect function with ground flag to calculate Z, else your traps will fly
i was used it, but players (atleast in pvp) moving randomly, and calculated pos sometimes wrong. it works for mobs

[aeo]

I thought about grabbing a 1 frame difference and going that way but this is a challenge and its fun. Both will probably have similar results. I maybe give your method a try though see how it works. Get the position 1 and 2 subtract 1 from 2 resulting in a velocity vector and multiply by trap speed? If you don't mind could you post some of your code, just a snippet don't want any c&p

[Wildbreath]

function PredictTrapPosition(unit)
    unit = unit or 'target'
    local x1, y1, _ = UnitPosition(unit)
    C_Timer.After(.1, function()
        local x2, y2, z = UnitPosition(unit)
        local px, py, _ = UnitPosition('player')
        local distance = math.sqrt((x2 - px)^2 + (y2 - py)^2)
        local trapSpeed = distance / 25
        local angle = atan2(x2-x1, y2-y1)
        local x = x2 + cos(angle) * trapSpeed
        local y = y2 + sin(angle) * trapSpeed
        WorldClick(x, y, z)
    end)
end 

for example, untested. without intersect with ground (api from offspring)
upd. added distance

also check for GetUnitSpeed(unit), forgot

[aeo]

Crazy, I Didnt know you could use this C_Timer I thought you were just going to do some GetTime subtraction. to count time passed and get updated position