API Reference — dna/layers/TwistSwingBehaviorWriter

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class DNAAPI TwistSwingBehaviorWriter : public virtual DefinitionWriter

Define how swing and twist deformation data is written into a rig's DNA. Implement this interface (via Writer) to supply or update the quaternion-driven joint rotation parameters that control twist and swing bone chains.

When to use this

Reach for this interface when authoring or replacing the twist/swing deformation setup for a rig — setting driver quaternion inputs, driven joint indices, and per-joint blend weights. If you are only reading existing data, use the corresponding reader interface instead.

Method groups

Group	Methods
Twist management	clearTwists, deleteTwist
Twist setup	setTwistSetupTwistAxis, setTwistInputControlIndices, setTwistOutputJointIndices, setTwistBlendWeights
Swing management	clearSwings, deleteSwing
Swing setup	setSwingSetupTwistAxis, setSwingInputControlIndices, setSwingOutputJointIndices, setSwingBlendWeights

Example

// Configure twist group at index 0: Y-axis, single quaternion driver, two driven joints
writer->setTwistSetupTwistAxis(0, TwistAxis::Y);

const std::uint16_t twistControls[] = {12, 13, 14, 15};  // quaternion [x,y,z,w] control indices
writer->setTwistInputControlIndices(0, twistControls, 4);

const std::uint16_t twistJoints[] = {3, 7};
writer->setTwistOutputJointIndices(0, twistJoints, 2);

const float twistWeights[] = {0.5f, 1.0f};  // one weight per driven joint
writer->setTwistBlendWeights(0, twistWeights, 2);

// Mirror configuration for a swing group
writer->setSwingSetupTwistAxis(0, TwistAxis::Y);
const std::uint16_t swingControls[] = {16, 17, 18, 19};
writer->setSwingInputControlIndices(0, swingControls, 4);

Constraints

• Control indices for both twist and swing inputs are always exactly 4 values, representing a single quaternion [x, y, z, w].
• Blend weight arrays must contain one entry per output joint in the corresponding joint index array.
• Parameter group storage is implicitly resized when a group index beyond the current count is written — no explicit resize call is required.

Watch out for

• Inherit from Writer, not directly from TwistSwingBehaviorWriter. Direct inheritance violates the intended interface hierarchy.
• Passing controlIndexCount != 4 for quaternion input methods may produce undefined results — the driver joint rotation is always encoded as a single quaternion.