Unity tracking components and build pipeline

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Build your Avatar from editable Sensa authoring components. NDMF reads the settings on the build copy, creates native Contacts, constraints, FX animation and menus, then removes the author scripts. This guide shows the build order, generated assets and the checks available at each stage.

Choose a measurement route

All three root prefabs accept an explicit Target within your Avatar: a bone/empty-object Transform, SPS Socket/Plug, Sensa Component or native Contact. Bones and ordinary markers can be selected directly. Native Contacts use their shape center; SPS targets use their authoring root geometry. Coordinates and units · Contact SDK reports

Use Automatic SPS Setup for several existing SPS targets, choosing SPS four-anchor tracking or Contact direct tracking for the group. Root-only measurement reads position and rotation; Plug length is required when tip tracking, paired Plug markers or grab handles are enabled. Configure Shader capture through its separate authoring prefab, with its own Producer ID and desktop rectangle.

Place and configure a prefab

1. Install the Unity package's VPM dependencies: NDMF 1.5.0+, Modular Avatar 1.10.0+ and matching VRChat Avatars SDK. Install official VRCFury when selecting SPS author targets. Contact direct tracking supports 3.10.6-beta.3 through advancedParameters, with compatibility for Beta.2's advancedProximityParameters.
2. Create your chosen route from GameObject → Sensa, or place its prefab inside the Avatar hierarchy. Check that Target selects the root you intend to measure.
3. SPS four-anchor tracking and Contact prefabs default to instance Root. Use distinct names such as Root, Chest and Hand for multiple points. An empty Collision Channel derives a stable channel from the instance name; enter an override when managing channels explicitly. Rename a duplicate to give it an independent automatic channel.
4. Give Shader capture a unique Producer Id from 1–65535 and pin the same ID in the desktop bridge. Follow Shader setup for presentation and capture registration.
5. Build the Avatar normally or use NDMF's processed preview. Inspect generated measurement components, then check parameters, calibrate and enable input through the desktop guide.

Keep the authoring host as an ordinary GameObject. Its Transform may be a measurement reference, and its generated Contacts, constraints and animation remain part of the build result.

Create a plane that follows a bone

1. Select a bone or SPS object inside the Avatar and choose GameObject → Sensa → Tracking Frame, or add SensaTrackingFrame.prefab.
2. Check Reference frame (reference). This single field accepts a Transform, SPS Socket/Plug, Sensa Component or native Contact. The menu fills a recognized selected target; when creating at the Avatar root, choose the reference yourself.
3. Set a unique Instance name (instanceName), default Frame, using at most 40 ASCII letters, digits, underscores or hyphens. Choose SPS four-anchor or Contact direct tracking as Tracking method (trackingMethod).
4. Place the centre with Origin offset (positionOffset) and adjust its orientation with Axis rotation (degrees) (rotationOffset). Both use the resolved root's local axes; the position offset applies before the added rotation. Six axis buttons choose a depth direction quickly, and Scene move/rotate handles allow finer adjustment.
5. Inspect the XY plane and +Z arrow in Scene: +Z is positive depth, +X is right and +Y is up. Axis marker distance (axisLength) is the Origin-to-Forward/Right distance in authored Avatar-root units, default 0.2 and configurable from 0.05 to 0.5.
6. Add a matching root prefab for measured target P on the same Avatar: SensaSpsRootProbe.prefab or SensaContactRootProbe.prefab. Assign its target and a separate instance name, such as Target; an existing measurement in the same coordinate frame can be reused.
7. After building, confirm valid desktop coordinates for the target, Origin and Forward. In Flow, expand Spatial calculation presets → Follow a moving plane, select the target and plane Origin, review the drafts, then save and connect outputs.

Generated points are named <name>_Origin, <name>_Forward and <name>_Right. A source reference follows bone movement and rotation. The measured frame lives under the Avatar root, following position and rotation through a ParentConstraint. Marker spacing follows uniform Avatar scale. Bone scale can move an offset origin; axis lengths retain the authored Avatar-root size. SPS authoring geometry retains its uniform-scale requirement.

Scene also shows coverage for the selected tracking method. Points used by the current calculation need valid coverage: the default template uses target P, Origin and Forward; Right provides the additional direction when needed. Each marker retains its own Sample check. Shorter axis spacing amplifies direction noise; compare known poses in the client to assess the default 0.2 spacing and behavior during fast movement. Choose one coordinate frame for the measured target and plane markers. Independent Point/Pose use their own ReferenceLocal frame for measurements directly within that reference. Depth, offset and angle calculations

How author scripts enter the build

Sensa authoring components implement VRC.SDKBase.IEditorOnly: SensaComponent, SensaAutoSetup, SensaFixedRootProbe, SensaContactRootProbe, SensaShaderCapture, SensaTrackingFrame, SensaPointProbe, SensaPoseSocket, SensaPosePlug and the internal lab fixture SensaQuickStart.

QuickStart remains an internal synthetic lab fixture. Use a root or tracking-frame prefab, or Point/Pose, for everyday tracking.

IEditorOnly identifies an author script; the NDMF plugin schedules generation. Retaining the host while removing only the author component lets bones, reference points and generated native components keep working.

Build order

Sensa has one NDMF generation entry point. NDMF and Modular Avatar are package dependencies; the SDK callback checks that generation completed.

Tracking frames use the same Generating entry: after standalone root authors and before automatic SPS setup, create the three points and remove the Tracking Frame author before base SensaComponent cleanup. Generated measurements retain the existing SPS/Contact protocols.

BuildContext.GetState records generation for each build. SPS four-anchor tracking, Contact, Shader and the other authors share this scheduler while keeping their own runtime protocols. The SDK -1026 check diagnoses remaining settings; actual generation always belongs to the early NDMF pass.

This ordering has also been checked in SDK 3.10.6-beta.3, NDMF 1.14.8, Modular Avatar 1.18.7 and VRCFury 1.1434.0 packages. Current VRCFury postpones SDK component cleanup to int.MaxValue. Sensa completes its own author cleanup and therefore also works with the SDK's default order. Other tools can register later SDK callbacks; Contact counting describes Sensa's NDMF checkpoint.

Assets and references

Generators operate on the build copy. Targets, bones, PhysBones and Raycast references must belong to that Avatar. The basic component validates references before creating native components so configuration errors are easy to locate.

Sensa creates temporary animator/menu/parameter inputs for MA and leaves build-asset serialization to NDMF. The native root Shader ships in the package at Runtime/Shaders/SensaRootTelemetry.shader; building references that asset directly. Rebuilding after a package update adopts the current encoder.

The basic SensaComponent binds native Contacts to their selected axis/bone so they continue following it. Related FX parameters are writable. Socket range and Contact sizes use the selected axis's local units, equal to metres at axis scale one; SPS four-anchor tracking and direct Contact tracking retain their separate coordinate contracts above. Supplementary Contact signals use tags matching their Senders. Existing-parameter signals reference the original parameter and retain its type.

SPS four-anchor and Contact root-scale checks follow a constraint's actual target and MA Merge Animator's relativePathRoot. Keep Avatar-root scale fixed while scaling child objects as needed. Shader sampling additionally validates original and quantized axes and uniform world scale, catching settings that would produce invalid packets during the build.

All three root routes validate native Contact offsets and rotations before generation. Offsets must be finite; rotation quaternions must be finite and nonzero and are normalized when read, preserving the authored Contact configuration. Shader capture also checks the final world basis inherited from the Avatar and its parents, catching accumulated nonuniform scaling that would keep encoded packets invalid. Sensa Pose Socket checks existing parameter declarations before generating any Receivers and reports duplicate names during the build. Instance names and pair channels use the specified ASCII characters.

Official sources and verification scope

The following official documentation and source were inspected on 2026-10-23 (China Standard Time):

These sources establish implementation and ordering. Unity EditMode contracts are written and have not been executed in Unity Editor for this change; see the verification record for actual results. Avatar upload, client OSC, rendering and device interactions receive separate acceptance checks.

Unity package · Automatic setup · Dependencies and measurements