Overview

Vehicles are special geometry objects, which are driven by scripts, which also determine the functionality.

Sample Files

• ma_HMMWV.rar

General Setup

Vehicles are complex objects that need careful setup in the 3d package. Basically, the setup should be applicable to any package. Polycounts need to be carefully calculated, as extended functionality increase object (drawcall) and polycount drastically.

Example: Rotation and position of the chassis pivot:

Every moving part needs to be a separate object within the 3d package. The pivot needs to be set correctly within the 3d package as the engine will use the object's individual pivot to make transformations.

Linking and Naming

For Maya what you have instead of linking is groups. Be sure that you have a _helper node encompassing your other assets. Basic hierarchy should look like this:

After everything is organized accordingly, you will have to include UDP (User Defined Properties) to the wheels, chassis etc...
(The UDP window can be found under the Crytek tab, make sure you have the Crytools installed)

• The parts need to be named in a logical way (chassis, wheel1, wheel2.., turret) as the objects will be referenced later in the Vehicle Editor and scripts.
• The scripts for damaged versions of vehicles expect an asset which contains the name of the intact model, plus the suffix "_damaged". (hull -> hull_damaged, door_left_1 -> door_left_1_damaged, etc).
  

Moving Parts

Every moving part needs to be a separate object within the 3d package. The pivot needs to be set correctly within the 3d package because the engine will use the object's individual pivot to make transformations.

Naming Conventions

Naming is needed for scripts to identify the objects and interact with them. The examples below reflect the asset names used in Crysis - they can be different for other games.

• The parts need to be named in a logical way (chassis, wheel1, wheel2.., turret) as the objects will be referenced later in the Vehicle Editor and scripts.
• The scripts for damaged versions of vehicles expect an asset which contains the name of the intact model, plus the suffix "_damaged". (hull -> hull_damaged, door_left_1 -> door_left_1_damaged, etc.).

Wheels Setup

• Place the wheel@_group object in the correct position.
• Place the wheel@_group's pivot in correct position (Center pivot). If you've frozen transforms, use the Pivot tool in the Crytek tab to retrieve the translation.
  IMPORTANT: The engine uses these coordinates as the position of the nodes, if your wheels transforms are 0,0,0 the helper node in the engine will be at the origin of the vehicle and will mess up the vehicle setup. The mass (or massbox in the sandbox vehicle editor) uses the positions of these wheel nodes to decide which wheels are steerable and which axles they use.
• Type "wheel" in the UDP window and click Save.
  

The wheel proxy must be simple enough to be recognized as cylinder by physics. Support for an additional detailed proxy (if the wheel's shape demands it) will follow.

Material Setup

• Create one Material group to include all of your materials which will be exported.
  
• The proxy material must have "Physicalize" turned on and the value set to "Physical Proxy (NoDraw)". To do this you must add an attribute to your material. Set the long name to "Physicalize" and Data Type as "String" and enter the string "Physical Proxy (NoDraw)" in your new attribute under "Extra Attributes".
• Operational break lights, headlights, different indicators on the dashboards have to be on different material IDs so code can identify them and deal with them (like setting glow value from code for example).

Physics Setup

Vehicles are complex objects and simplifying collision calculation is very important for performance. Therefore it is advisable to create two physics proxies. one is for collision with the terrain and characters, one for collision with bullets, grenades...

• Vehicles must have a very simple physics proxy which is called "hull_proxy". This is a separate, collision object for character and terrain collision. It should be slightly larger than the enclosed detailed proxies. Polycount for this proxy must be fairly low. For land-based vehicles like cars, tanks and hovercrafts, the proxy should not have parts sticking out in places which can frequently bounce into and slide across walls, like the front and side parts of a truck cabin.
• For collision detection of bullets, grenades, the hull, etc - object should contain a more detailed embedded physics proxy. It should resemble the shape of the vehicle more closely, small elements could be left out. It should certainly include cutouts, like holes for the doors, windows, and other open areas.
• Attached parts like doors and bumpers need an own simplified proxy in case the embedded proxy is too detailed and calculation heavy for terrain/water collision. In this case, add the suffix "_proxy" to the object name.
  
• Proxy material must have "Physicalize" turned on in the shader options within the 3d application (please refer to the Material setup section); the type should be set to "Physical Proxy (NoDraw)".
• LOD's do not have to contain proxies, as it will be used from the LOD0. In versions with lower performance settings, where LOD1 is used as the base mesh, the proxy from the High Spec LOD0 is taken into account.
• Damaged model has to contain its own proxy to follow deformed/different geometry (LOD's do not need a proxy).

LODs

• For general information refer to the section. For specialities in vehicle creation, please see below.
• Because of the asset complexity it is recommended to link subsequent LODs to the LOD0 version and include the LOD0 name in the suffix. (i.e. "hull" has LODs linked to it called _lod1_hull; _lod2_hull).

Vehicle Damage Model

The damage model for vehicles is a separate asset which replaces the vehicles on destruction. It can be a simple static model or a complex prebroken object.

• It replaces the original model and therefore needs a separate proxy model.
• The damaged objects needs the suffix "_damaged" to its name. (like hull -> hull_damaged, door_left_1 -> door_left_1_damaged, etc.)
• To have some extra debris (if one object is breaking apart to more debris parts), you can add further objects to the damaged model. These should be called the object's name + "debris_" suffix. (hull -> hull_debris_1, hull_debris_2, etc.) These will spawn and fly away from the blast when the vehicle explodes.

• The damage model can also include LOD's

• If the damaged model is very big (i.e. 10m wide, 6m high), an can be added by naming it $occlusion and linking it to the damaged model.Occlusion proxy is allowed to have open edges and need to be as low as possible (something around 2-10 polys).

Animations

• TBC controller for the animations (translation and rotation) must be used. Any other controller will create unpredictable results. Please refer to Animation guide for more details!
• Animations have to be saved as .anm files. To save certain animations, you must select the objects you would like to save the animations of, and add to the export list. If you want to animate the doors closing, then you have to export with only the doors in the export list. File names has to start with the object names + the animation's name. If the vehicle's main file is called car.cga, then the animation should be called like car_door_opening.cga for example.
• Once you animated your objects, you have to export the default state. It has to be called the same like the object .cga file (if the object is tank.cga then the default animation has to be tank.anm ). This default state has to contain all the animated objects.
• Please see exporter documentation for further exporting features and parameters!

Position Helpers for Characters

• Character sitting and enter positions need to be indicated with locators and must be a child of the hull node.

Export Options

Vehicles are very complex objects and can cause major problems, if the exporting is not done carefully. To avoid complications in the scene:

• Add the root node to the export window and check Custom File Name. Choose an appropriate filename and export.
• Vehicles except Tanks: Export all parts as one cga. uncheck "file per Node" and "merge all nodes".
• Tanks: Export all parts except the tank treads together as one cga.uncheck "file per Node" and "merge all nodes".
• Tank Treads: Export right and left tank tread separately as chr. uncheck "merge all nodes"; check "file per node" if you like. Choose only the tank treads object, not the wheels or the bones.
• Choose the top node and relevant helpers and export only these. the linked children will be exported automatically.

Setup in Sandbox

In order to work properly, a vehicle script is required. Otherwise the vehicle can only be judged visually as a Geom Entity.

• Drag and drop the item from the entity section in the Rollup Bar or the Entity Library (in the ) into the level.
• If no script is available, drag and drop the asset from the Geom Entity section in the Rollup Bar into the level.

Please refer to section for information on the vehicle editor.

Debugging

There are some useful commands you can use to check your asset, and see if it works as expected. Some of these are listed below. (You can turn off any of these drawing modes by entering 0 after the command instead of the number given here!)