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Overview

We want to have assets that take the lowest amount of memory, but that animate at the highest possible quality.

Uncompressed, an animation contains a key for every frame in the animation and for each joint that has been exported. We usually want to reduce the amount of joints and keys to minimize the size. We have separate channels for rotation keys and position keys per joint.

To compress animations for characters we use the Resource Compiler tool (RC).



Sections

Table of Contents
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Compression of Existing Animations

To adjust compression settings of the animation, load your character by double-clicking on it in the Asset Explorer.

Choose your animation in the Animations tree in the Asset Explorer. Note that both *.i_caf and *.animsettings should present and writable. (Not inside a *.pak file)


Note

Note for Perforce users: *.i_caf and *.animsettings files should be synced and checked out locally. If they are not, use a perforce client to do so first.


Compression settings




  • You can adjust compression settings and instantly see the resulting animation and its size...
  • In the display options, set Compression to Side by Side to compare the original animation with the compressed version.


Compression Side by Side

You can remove specific per-joint compression settings via the context menu

Per Joint Compression Settings

Click the Save button in the properties panel toolbar, or Save All in the File menu when you're done

Setting the Compression Settings

Removing channels (position/rotation keys) automatically

  • You can get huge savings by automatically removing joints that don't contribute to the animation.
  • Roughly, for the RC to know if a joint contributes to an animation, it finds out how much it moves during the animation and compares it to the provided epsilon valuesprovided values. If it finds that it moves less than what the epsilon specifies, it will remove the keys for the joint. Higher values for epsilons will remove more joints.
  • The values to tweak for this are Position Epsilon for the position channel and Rotation Epsilon for for rotation channel. This means rotation and position keys are considered separately.
  • Position Epsilon and and Rotation Epsilon are are global values for the whole animation.
  • Additive animations have smaller movement so you'll need to use smaller values for the epsilons.
  • This is an all or nothing process: Either the keys are all kept for a channel(position/orientation), or deleted.

Reducing the amount of keys within a channel

  • The previous step has removed joints completely. We now want to reduce the number of keys each channel has, since at this point we have one key per frame.
  • For this the RC uses the Compression value. Higher values will remove more keys within a channel.
  • The Compression value is a global value so it will affect all joints the same by default (although we can still tweak it later on a per joint detail level).

The goal should be at this point to have an animation that takes as little as possible but looks good. Sometimes though, playing around with global values for a whole animation is not enough, and we will need to fix up individual joints that show choppy motion.


Per-Joint Setup

Per joint control over the

epsilons

removal process

  • For each joint, by default, the epsilon values are used to decide if they are removed or not.
  • We can force a joint to be removed by clicking the checkbox next to it. Position and Rotation channels will both be removed for the selected joints.

Per joint control over the compression value

  • For each joint we can specify a multiplier that is applied to the Compression value. By default this value is 1, so a joint uses the global Compression value.

Define Animation Tags

Each animation can have a list of tags associated with it. Tags can be used to:

  • Select animations that have to go into a specific DBA by means of an Animation Filter (see below)
  • Apply compression to a group of animation files by means of Compression Presets (see below)

You can find Tags in the Properties window when you select animation in the Asset Explorer.

To add a new tag use the context button with tag count and select Add in the popup menu:

Pic4: Adding a tag

Then click on an empty string to enter its name.

To remove a tag you can use the context menu (RMB on the tag name):

Pic5: Removing a tag


Tip

For curious readers: tags are case insensitive. I.e. the tag "CINEMATIC" will be treated the same way as "cinematic".

Batch-compression

Compression Presets can be used to apply the same set of compression rules to multiple animations at once. You can locate them in the Compression section of the Asset Explorer.

Each compression preset entry defines a filter that can match animations according to a certain filter, i.e. a set of criteria such as folder, filename or tags. Such criteria can be combined using logical operations into a complex condition, like "in folder and doesn't contain specific tag but has sub-string in name". When multiple presets match the same animation only the first one is used. You can always preview which compression setting entry was applied to an animation in the animation properties (by selecting a specific animation in the asset explorer).

Compression presets are saved in: <GameFolder>\Assets\Animations.pak\CompressionPresets.json.