Twist Corrective

Describes how the Twist Corrective control can be used to drive curve values based on the twist of one bone relative to another.

Twist Corrective

With the Twist Corrective Animation Blueprint node, you can drive Animation Curves, like Morph Targets, using the transform of a delta angle calculated using a Base Frame and Twist Frame against the direction of a Twist Planer.

twist corrective animation blueprint node

Overview

Using the Twist Corrective node, you can drive Animation Curves values, such as Morph Targets, based on the twist of one bone relative to another.

Here is an example of a character's scarph morph targets adjusting as the head bone is twisted, to create a more natural look.

twist corrective disabled twist corrective enabled
Disabled Twist Corrective Enabled Twist Corrective

Example Workflow

The Twist Corrective node operates within Component Space, so a space conversion will need to occur to implement the node within your character's Animation Blueprint.

First, you must select a bone to act as the Base Frame, to calculate the twisting bone's alpha from. It is also important to define on what axis the motion the twist alpha will be in reference to. In the Axis property define which axis the motion will occur by setting the value to 1. In the provided example the neck_02 bone was used and the Z-axis was given a value of 1.

base frame settings in the twist corrective animation blueprint node details panel

Next select the bone that is undergoing the twist motion as the Twist Frame Bone, in the example the head bone is used. You must also define the axis of motion, in this case the property will replicate the Base Frame Axis with only a value of 1 on the Z-Axis.

twist frame settings in the twist corrective animation blueprint node details panel

You must also set the twist plane as a reference point, to calculate the alpha motion. In the example, the Y-Axis was enabled by setting a value of 1 in the Y-Axis field.

twist plane normal axis settings in the twist corrective animation blueprint node details panel

Finally, you must input the name of the Animation Curves. In the workflow example, the morph target C_BipedHeadNeck_A_NeckMid_Jnt_n11_44_n1 is used.

curve name settings in the twist corrective animation blueprint node details panel

After compiling the Animation Blueprint the effects should be visible as the head bone rotates on the Z-Axis in the viewport.

Property Reference

twist corrective animation blueprint node details panel

Here you can reference a list of the Twist Corrective node's properties.

Property Description
Base Frame

The Base Frame series of properties defines the reference point to calculate the motion alpha of the Twist Frame.

In the Bone property, you can select the bone to use as the Base Frame from the characters skeleton.

In the Axis property, you can select what axes of motion to calculate motion. A value of 0 will not calculate motion, a value of 1 will calculate positive motion, and a value of -1 will calculate negative motion.

You can also enable the In Local Space property to calculate motion in local space, or disable In Local Space to calculate motion in world space.

Twist Frame

The Twist Frame series of properties defines the twisting bone to calculate the motion alpha from in relation to the Base Frame and Twist Planer Normal Axis.

In the Bone property, you can select the bone to use as the Twist Frame from the characters skeleton.

In the Axis property, you can select what axes of motion to calculate motion. A value of 0 will not calculate motion, a value of 1 will calculate positive motion, and a value of -1 will calculate negative motion.

You can also enable the In Local Space property to calculate motion in local space, or disable In Local Space to calculate motion in world space.

Twist Planer Normal Axis

Here you can set the normal of the plane to calculate the angle alpha of the Twist Frame from the Base Frame.

In the Axis property, you can select what axes of motion to calculate motion. A value of 0 will not calculate motion, a value of 1 will calculate positive motion, and a value of -1 will calculate negative motion.

You can also enable the In Local Space property to calculate motion in local space, or disable In Local Space to calculate motion in world space.

Max Angle in Degree Set the maximum limit of the twist that will output a value to the Curve. For example, the degree at which the twist should result in the maximum curve value being outputted. Values cannot exceed 180.
Mapped Range Min Minimum value to apply to the curve. A value of 0 being the beginning of the curve and a value of 1 being the end of the curve.
Mapped Range Max Maximum value to apply to the curve. A value of 0 being the beginning of the curve and a value of 1 being the end of the curve.
Curve Input the name of the Curve or Morph Targets you wish to apply the Mapped Range Min and Mapped Range Max based on the calculated twist alpha from the Twist Frame Bone.
  • animation
  • animation blending
  • skeletal control

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