API Reference — dna/layers/TwistSwingBehaviorReader

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class TwistSwingBehaviorReader : public virtual DefinitionReader

Read-only accessors to the swing and twist data associated with a rig — which joint rotations drive twist/swing transformations, which joints they output to, and the blend weights applied.

When to use this

Use this when evaluating how a driver joint's rotation should propagate twist or swing onto other joints — for example, distributing a forearm's twist along multiple joints in a chain. Implementors should inherit from Reader itself, not this class directly.

Method groups

Group	Methods
Twist	getTwistCount, getTwistSetupTwistAxis, getTwistInputControlIndices, getTwistOutputJointIndices, getTwistBlendWeights
Swing	getSwingCount, getSwingSetupTwistAxis, getSwingInputControlIndices, getSwingOutputJointIndices (and corresponding blend weights)

Example

// reader implements Reader, which composes TwistSwingBehaviorReader
for (std::uint16_t twistIdx = 0u; twistIdx < reader->getTwistCount(); ++twistIdx) {
    auto axis = reader->getTwistSetupTwistAxis(twistIdx);
    auto drivenJoints = reader->getTwistOutputJointIndices(twistIdx);
    auto weights = reader->getTwistBlendWeights(twistIdx);
}

Parameters

Name	Type	Description
twistIndex	std::uint16_t	required — position of the twist parameter group; must be less than getTwistCount.
swingIndex	std::uint16_t	required — position of the swing parameter group; must be less than getSwingCount.

Returns

std::uint16_t / TwistAxis / ConstArrayView<std::uint16_t> / ConstArrayView<float> — counts, axis, driver/driven joint index views, or blend weights, depending on the accessor called.

Watch out for

• The raw control indices representing the driver joint rotation are always exactly 4 values, corresponding to a single quaternion's [x, y, z, w] attributes.
• There is exactly one blend weight per output joint in the returned list — the two lists are parallel and must be indexed together.
• All index parameters (twistIndex, swingIndex) must be strictly less than the value returned by getTwistCount() or getSwingCount() respectively. Passing an out-of-range index is undefined behavior — validate with the count getter before each call.
• Do not subclass TwistSwingBehaviorReader directly. Implementors must subclass Reader; this class is an intermediate layer in the interface hierarchy.