Motion Blending #

In overlaying motions, there can be conflicts in the actions directed by multiple motions. For example, in the example of the “Motion Overlay” page, when overlaying a walking motion and a hand waving motion, the actions of swinging the arm back and forth by walk.vmd and the action of raising the hand and waving it left and right by onehandwave.vmd overlap for the right arm bone of the character.

This article explains how to resolve such overlapping actions.

Overwrite, Add, Multiply #

The default behavior in the event of overlap is “overwrite”. That is, the motion with the highest priority is adopted, and all other motions are ignored. The motion that started last has the highest priority. In the example, the action of waving left and right by onehandwave.vmd was prioritized over the action by walk.vmd.

You can change this behavior upon overlap by issuing a MOTION_CONFIGURE message after adding the motion. You can specify one of the following three types.

MODE_REPLACE: Overwrite
MODEL_ADD: Add
MODEL_MUL: Multiply (morphs only)

The default MODE_REPLACE overwrites the lower-ranking motion. If you specify MODEL_ADD, the motion will be “added” to the movement of the lower-ranking motion. MODEL_MUL multiplies the morph value indicated by this motion by the amount of morph calculated from the lower-ranking motion.

MOTION_CONFIGURE|(model)|(motion)|MODE_REPLACE
MOTION_CONFIGURE|(model)|(motion)|MODE_ADD
MOTION_CONFIGURE|(model)|(motion)|MODE_MUL

For example, addition can be used to add fluctuation or adjust offset, which can do similar things to “Multi-stage bones” in MMD. Also, multiplication can be used to “specify 0 to disable the morph changes of some lower-ranking motions”.

Blend Rate #

Along with the above specifications, you can also specify a blend rate for each motion. The blend rate can be any value from 0.0 to 1.0, with 1.0 being the default if not specified.

MOTION_CONFIGURE|(model)|(motion)|MODE_REPLACE|(rate)
MOTION_CONFIGURE|(model)|(motion)|MODE_ADD|(rate)
MOTION_CONFIGURE|(model)|(motion)|MODE_MUL|(rate)
MOTION_CONFIGURE|(model)|(motion)|BLEND_RATE|(rate)

When stacking motions, the processing such as overwriting or addition is performed after multiplying by this blend rate. Specifically, it works as follows:

MODE_REPLACE + specified rate: The motion is overwritten with the movement obtained by multiplying the motion amount by the rate
MODE_ADD + specified rate: The movement obtained by multiplying the motion amount by the rate is added
MODE_MUL + specified rate: The change indicated by the motion is multiplied by the change obtained by multiplying the rate

Also, you can change the value of the rate without changing the setting with BLEND_RATE.

Bone-level Control #

Additionally, while the above is a specification for the entire motion, you can also set details on a bone-by-bone basis. Please refer to the reference for details.