Vehicles (programming)

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This article is meant to give an in-depth analysis of the vehicles in Source and to provide the necessary information to create and modify source vehicles.

In General

All vehicles, including the airboat, inherit from the same base classes:

Note:Note that abstract interfaces aren't properly represented here as separate nodes. However, classes that inherit from an interface will have it listed under its name along with every other parent class.

At the end of the day, the typical source vehicle is made up of 3 parts:

• The main vehicle, inheriting from CPropVehicleDriveable.
• The "Server" Vehicle, inheriting from CBaseServerVehicle.
• The vehicle physics, CFourWheelVehiclePhysics.

prop_vehicle_driveable Entity

This is the main part of the vehicle, it's the entity that has the actual name of the vehicle and inherits from CPropVehicleDriveable. Like CPropAirboat.

This entity doesn't handle passengers or passengers entry, since the code the player used to ride vehicles needs a IServerVehicle. That's why there is a member pointer on a CFourWheelsServerVehicle stored in the instance.

Server Vehicle

This class's primary purpose is to handle passenger entry, and sound state, along with acting as a proxy between the Driveable Vehicle, and the physic vehicle. It uses data structures named operating, control, and vehicle params, to share information between the driveable and physics classes. Its other purpose is to trigger the loading of the vehicle script data on its creation, along with the creation of the physics vehicle object.

Vehicle Physics

This class isn't an entity, it's mostly a wrapper between the driveable and server vehicle entities and the vehicle physics controller (IPhysicsVehicleController). It transmits data from the IPhysicsVehicleController object (that's in the physics DLL) through the GetVehicleOperatingParams() method. It also transmits to the IPhysicsVehicleController the data in the control params (m_controls) structure. This object is responsible for loading and parsing the physics vehicle data, through the bool ParseVehicleScript( const char *pScriptName, solid_t &solid, vehicleparams_t &vehicle ) method.

Vehicle Data Structures

Todo: Info on the data structures used to transmit physic data and controls data back and forth between the physic DLL and the server DLL. See "..\src\public\vphysics\vehicles.h" and "..\src\game\server\vehicle_sounds.h"

Vehicles Specifics

Vehicles types values

From "..\src\public\vphysics\vehicles.h"

#define VEHICLE_TYPE_CAR_WHEELS			(1<<0)
#define VEHICLE_TYPE_CAR_RAYCAST		(1<<1)
#define VEHICLE_TYPE_JETSKI_RAYCAST		(1<<2)
#define VEHICLE_TYPE_AIRBOAT_RAYCAST	(1<<3)

The Buggy and Jalopy

The buggy

Todo: Buggy and Jalopy specifics.

The Airboat

The airboat uses the same physical entity as the buggy CFourWheelVehiclePhysics. But it changes the vehicle type value to VEHICLE_TYPE_AIRBOAT_RAYCAST.

Todo: airboat specifics.

Player Interaction

Todo: describe what goes on when the player uses a vehicle.

Vehicles Components

Interfaces

• IClientVehicle - Client Side
• IVehicle - Vehicle Generalizations
• IServerVehicle
• IDrivableVehicle
• INPCPassengerCarrier
• IPhysicsVehicleController

Classes

• Server:
  • CFourWheelVehiclePhysics
  • CBaseServerVehicle
  • CFourWheelServerVehicle
  • CPropVehicle
  • CPropVehicleDriveable
• Client:
  • C_PropVehicleDriveable

Additional Help

Source code:

Multi-passenger vehicles

• The Jurassic Rage coding team has released their multi-passenger vehicle code:
  • Here is the forum thread (archived)
  • Here are the files (archived) [mirror #1]
• Multipassenger Vehicle Abstract

Pilotable code

• TheQuartz, creator of the Pilotable Strider Mod, has released the "Strider, Helicopter, and APC" source code:
  • Here is the blog post (archived)
  • Here are the files (archived)

Fixes:

Half-Life 2 SDK vehicles

• Some information on fixing source vehicle code for use in Multiplayer can be found here.

HL2DM vehicle fix

• A partial fix to make vehicles predicted and work in HL2DM can be found here.

External links

• Design3 Vehicle Programming Video Tutorials