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Overview

The pre-baked physics pipeline allows you to bake out a physics simulation in a 3D asset creation package to keyframe data, and load it into CryENGINE. Once the pre-baked physics is in the engine, the pieces can be detached from the animation become physicalized.

The Destructible Object

  • The model should be broken up into pieces in an interesting way (The break points should make sense, think about how the material would break).
  • The pieces should have very low-res physical proxies, try to use boxes whenever possible.
  • Make sure the Crytek Shader material for all objects is set to "physical".

Setting Up the Simulation in 3ds Max

Creating a Rigid Body Collection

  • Select all of the objects that you would like to be simulated and then select reactor -> Create Object -> Rigid Body Collection.
  • Any object that you do not want to move can be set to "unyielding" in the reactor rollout utility.
  • It helps to put a large flat cube down as an "unyielding" floor.
  • In the reactor utility roll-out you can give your items "mass" and other properties.

Applying a Force to the Rigid Bodies

The reactor is very simple when it comes to applying a force to your objects; there are two basic ways:

  • Wind: You can create a Wind force by selecting reactor -> Create Object -> Wind.
    • Wind values can be keyframed over time when changed in autokey mode.
  • Animated Objects: You can animate other rigid body physical objects to collide with your object in order to create an interesting simulation.
    • Animated items should be set to "unyeilding" in the reactor utility rollout, if not, upon hitting a rigid object, they will start to simulate and not stick to their keyframed animation.
    • Character bones can be physicalized and used if you have a cinematic sequence where a character interacts with your breaking object.
    • Spheres can be used to break apart buildings, simulating explosions (delete these spheres after the simulation).

Previewing the Simulation

  • Select reactor -> Preview Animation... to see a preview of your simulation.

Baking the Simulation to Keyframe Data

  • Select reactor -> Create Animation and wait for it to bake your simulation to keyframe data.

Note

This cannot be undone, so save a copy of your scene before baking it to keys.

 

Exporting to CryENGINE

Here are some things to keep in mind when exporting your pre-baked physics into the engine:

  • You will export the animation as a CGA:
    • All the position and rotation controllers of the objects in the CGA need to be set to TCB. The easiest way to do this is with the CryAnim Tools (On the General Tools rollout).
    • Select merge all nodes in the export options.
    • Turn off all bone export options, but tell it to export every '1' frames.
    • Select one object that is not moving and parent all the other pieces to it. This object can be one you set to "unyeilding". In buildings use the foundation.
  • You can add special metadata to your individual CGA objects, either through the Meta Data Editor found in CryTools (Rigging Tools), or by using these flags in the User Defined Properties of an object:
    • Mass
    • Box
    • Entity
  • The current animation will show up as Default in the CGA you export, no CAL file is needed to play it.
  • Name your CGA with the same name as the original object, this way the material will work with it.
  • Open your CGA in the Character Editor and play the animation labelled "Default", you should see your animation play.
  • As always, obey the Character Rigging Guidelines for CryENGINE; pay particular attention to having no scales and transformations.

Creating an AnimObject Entity

Once you have exported the CGA, place it into the engine as an AnimObject.

  • Drag in and place an AnimObject from Entity Panel -> Physics -> AnimObj.
  • Remember that ActivatePhysicsThreshold is a fraction of gravity, thus a heavier piece will be harder to activate since the gravity force that acts on it is stronger.
  • Mass is the overall value for the entire CGA, for instance, a Mass of 100 on a CGA with 100 pieces would yield 1kg per piece.
    • You can set the mass in the UDP metadata of your CGA as mentioned above.

Entity Properties

 

Name

Description

n

ActivatePhysicsDist

[FLOAT] - This is the distance from the pivot (in meters) after which the objects are forcefully detached from the animation.

n

ActivatePhysicsThreshold

[FLOAT] - The amount of force needed to physicalize an object. This value is a fraction of the current gravity.

?

AutoGenAIHidePts

[BOOL] - The amount of force needed to physicalize an animated object.

?

Model

[MODEL] - The CGA model you created.

?

ModelFrozen

[MODEL] -

?

Pickable

[BOOL] - Defines whether or not the object can be picked up.

Ai

Pickable

[Smart Object Classes] -

?

Usable

[BOOL] - Defines whether or not the object can be used.

ab

UseMessage

[String] - The message displayed when the object is in the crosshairs for use.

 

Animation

 

?

AlwaysUpdate

[BOOL] -

ab

Animation

[String] - The animation to be played, in this case it is usually Default.

?

Loop

[BOOL] - This will cause the animation to loop.

?

PhysicalizeAfterAnimation

[BOOL] - Select this to physicalize all of the pieces after the animation has played.

?

Playing

[BOOL] - With this selected, the animation will start immediately.

n

Speed

[FLOAT] - A multiplier for the playback speed of the animation.

ab

playerAnimationState

[String] -

 

Physics

 

?

ActivateOnDamage

[BOOL] - With this selected, any piece damaged will immediately become physicalized and detach from the animation.

?

Articulated

[BOOL] - You need to have this selected if you are using a CGA, however, it is not selected by default.

n

Density

[FLOAT] - Can be used instead of Mass (if mass is -1) to set the density of each node.

n

Mass

[FLOAT] - This is the overall mass for the entire CGA.

?

Physicalize

[BOOL] - Selects whether or not the CGA can become physicalized.

?

PushableByPlayers

[BOOL] - Allows the object to be pushed by players.

?

Resting

[BOOL] - Whether the object is resting initially (it is better to have it set).

?

RigidBody

[BOOL] - If deselected, the object is static. Pre-baked physics objects must have it selected.

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