Internal Animation Format

Overview

From a programming perspective, there are several steps to uploading an animation from a BVH (BioVision Hierarchy) file:

1. Read and parse the BVH file, creating an LLKeyframeMotion object containing the motion data.
2. Gather input from the user (via the upload preview floater) for things like animation priority, facial expression, and looping; these settings are stored in the LLKeyframeMotion object.
3. Serialize the LLKeyframeMotion object as LLSD.
4. Upload the serialized data to the asset server.

Before other viewers can play an animation, they must:

1. Download the serialized data from the asset server.
2. Deserialize it to an LLKeyframeMotion object.

Relevant source files:

• linden/indra/llcharacter/llbvhloader.cpp
• linden/indra/llcharacter/llkeyframemotion.cpp.

Header

The first part of the animation data is a header describing various details about the animation as a whole. The elements, in order, are:

• version
• sub_version
• base_priority
• duration
• emote_name
• loop_in_point
• loop_out_point
• loop
• ease_in_duration
• ease_out_duration
• hand_pose
• num_joints

Joint Data

After the header is data for each joint in the skeleton:

• joint_name
• joint_priority

Joint Rotation Keys

At the start of the rotation data is the total number of rotation keys:

• num_rot_keys

Then, for each rotation key:

• time
• rot_angle_x
• rot_angle_y
• rot_angle_z

Joint Position Keys

At the start of the position data is the total number of position keys:

• num_pos_keys

Then, for each position key:

• time
• pos_x
• pos_y
• pos_z

Constraints

After the joint data are a number of entries for joint constraints (whatever that means):

• num_constraints

Then, for each joint constraint:

• chain_length
• constraint_type
• source_volume
• source_offset
• target_volume
• target_offset
• target_dir
• ease_in_start
• ease_in_stop
• ease_out_start
• ease_out_stop