Overview
Previzion’s scene animation system enables objects in the 3D scene to be driven by external sources of animation over a standardized network data protocol. This enables the use of external character animation tools such as Autodesk Motionbuilder or motion capture devices as animation sources, while still using Previzion’s rendering and video synchronization tools.
Data Protocol
Previzion’s data format uses a series of UDP packets, one for each frame of animation. Each packet is formatted in XML, with formatting very similar to that of a Collada document, and contains a series of data tags:
- A frame timecode tag (optional)
- An object node name, specifying the transform that the animation data will be applied to
- A 4×4 Collada-formatted transformation matrix that describes the complete scene position, orientation, and scaling of the object”s transform
An example of a packet is provided below.
The general construction of the packet is very similar to a Collada document, and the use of a standardized matrix transformation removes the possibility of confusion from various Euler angle interpretations. The use of the named node ID tag also means that routing the data to the correct scene transform is straightforward.
Supported Animation Types
Previzion presently supports rigid body animation, for on set previsualization purposes. Skinned animation is planned for a future point.
Rigging
Since skinned animation is not presently supported, when rigging characters in 3D applications, a skinning modifier is not used. Instead, the various body components are modeled as separate components, and parented to the corresponding joints on the skeleton.
The above image shows how the geometry is parented to specific bones. The recommended bone naming convention is simply to use MotionBuilder’s standard bone naming convention; this way characters can be rapidly and automatically characterized to control rigs inside MotionBuilder.