Multiplayer Vehicle Fixes

These fixes are to correct some issues with using Valves vehicle code in a multiplayer game. A true way of doing vehicles in Source Multiplayer would be to write prediction code for the client, but this is not possible with the current engine. The only other option would be to write your own vehicle movement code, which is no easy task for complicated vehicles like the buggy. Research was made into the possibility of predicted physics simulations between the server and client with poor results. Half-Life 2 Rally closed 27 Dec 2006 and has written a list of critical problems they experienced here.

Laggy Vehicle View

A couple of changes will fix the laggy view, but present different issues. One being the cameras position no longer interpolating to where it should.

Open cl_dll/c_prop_vehicle.cpp

Find C_PropVehicleDriveable::C_PropVehicleDriveable() constructor.

Replace

	m_ViewSmoothingData.bDampenEyePosition = true;

with

	m_ViewSmoothingData.bDampenEyePosition = false;

Open cl_dll/c_prop_vehicle.h

In class C_PropVehicleDriveable replace

	virtual bool IsPredicted() const { return false; }

with

	virtual bool IsPredicted() const { return true; }

Vehicle Camera affecting other players

A simple fix is to make sure the vehicles view changes only affect the local player.

Open cl_dll/c_prop_vehicle.cpp
(Note: As Of 7/05/2009 Using the Orange Box Source SDK build this section is in file vehicle_viewblend_shared.cpp -- line 291 of function "void SharedVehicleViewSmoothing". I recommend you do not make these changes, it causes compile errors, simply make the edits in the next step (SharedVehicleViewSmoothing function in c_prop_vehicle.cpp) --Digi & tymaxbeta)

Find void VehicleViewSmoothing

Replace

	if ( !bExitAnimOn )
	{
		Vector localEyeOrigin;
		QAngle localEyeAngles;

		pData->pVehicle->GetAttachmentLocal( eyeAttachmentIndex, localEyeOrigin, localEyeAngles );
  		engine->SetViewAngles( localEyeAngles );
	}

with

	if ( pPlayer->IsLocalPlayer() )
	{
		if ( !bExitAnimOn )
		{
			Vector localEyeOrigin;
			QAngle localEyeAngles;

			pData->pVehicle->GetAttachmentLocal( eyeAttachmentIndex, localEyeOrigin, localEyeAngles );
  			engine->SetViewAngles( localEyeAngles );
		}
	}

Find C_PropVehicleDriveable::GetVehicleViewPosition

Replace

	VehicleViewSmoothing( m_hPlayer, pAbsOrigin, pAbsAngles, m_bEnterAnimOn, m_bExitAnimOn, &m_vecEyeExitEndpoint, &m_ViewSmoothingData, &m_flFOV );

with

	if( m_hPlayer->IsLocalPlayer() )
	{
		VehicleViewSmoothing( m_hPlayer, pAbsOrigin, pAbsAngles, m_bEnterAnimOn, m_bExitAnimOn, &m_vecEyeExitEndpoint, &m_ViewSmoothingData, &m_flFOV );
	}

For Orange Box:

Replace

	SharedVehicleViewSmoothing( m_hPlayer, pAbsOrigin, pAbsAngles, m_bEnterAnimOn, m_bExitAnimOn, m_vecEyeExitEndpoint, &m_ViewSmoothingData, pFOV );

with

	if( m_hPlayer->IsLocalPlayer() )
	{
		SharedVehicleViewSmoothing( m_hPlayer, pAbsOrigin, pAbsAngles, m_bEnterAnimOn, m_bExitAnimOn, m_vecEyeExitEndpoint, &m_ViewSmoothingData, pFOV );
	}

Client Side

You must also ensure that sv_client_predict is set to 0 otherwise the vehicle view will still be laggy.

	sv_client_predict 0

Once this setting was enabled I tested with the airboat which became completely smooth (Source SDK 2013 via GitHub). There is no need to add a point_viewcontrol entity as suggested in the HL2DM_Vehicle_Fix follow on tutorial. Here's a video showing the airboat in action.