Vertex animation

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Vertex animation is the keyframed animation of individual vertices of a mesh. It's good for very complicated motion like that of cloth, hair, or water. It should not be confused with flex animation, which deforms a mesh from one shape to another by moving its vertices in straight lines.

Vertex animation was added in Source Filmmaker and is also available in Dota 2.

Bug:
Using the $scale command breaks vertex animation.

To do: Add documentation on DMX vertex animation method which is compatible with $scale.

Implementation

  1. Create a vertex animation in your modelling tool.
  2. Export a Vertex Cache file. Currently only the official Maya exporter can do this, and only to SMD.
  3. Add the vcafile command to your $model block (see example below).

This produces two flex controllers named after your VCA file. The first defines the blend weight of the animation, the second (prefixed with multi_) defines the active frame.

A programmer can now control your animation. If you need to map the vertex animation to a standard animation sequence, perform these extra steps:

  1. Add a new bone which will drive the vertex animation. It doesn't need to have any vertices attached.
  2. Add two $boneflexdriver commands to bind your vertex animation to the new bone (see example).
  3. Add at least one $sequence in which the new bone is animated in its X and Y axes. Its X position defines the blend weight of the vertex animation (0-1), and its Y position defines the frame of vertex animation (0-1).
    Bug:
    Currently the flex driver sequence must be defined with $upaxis Y. This doesn't affect the rest of the model.

Example

$model "body" "ref_mesh.smd" {
	vcafile "vertex_animation.vta"
}
 
// Optional:
 
$boneflexdriver "flexAnimBone" tx "vertex_animation" 0 1
$boneflexdriver "flexAnimBone" ty "multi_vertex_animation" 0 1
 
$upaxis Y // currently flex driver sequences must be Y-up
$sequence "vertex_animation" "flexAnimBone_anim.smd"

Example Videos

See also