---
pretty_name: Lance Captured Trajectory Dataset
language:
  - en
tags:
  - lance
  - trajectory
  - mano
  - robotics
  - motion-capture
task_categories:
  - robotics
  - time-series-forecasting
---

# lance_dataset

This repository stores Lance datasets.

The current dataset is organized as `Dexcanvas.lance/`. It contains Lance data fragments, version manifests, and transaction metadata.

## Dataset Structure

`Dexcanvas.lance` represents a captured trajectory dataset. Each row corresponds to one complete captured trajectory. The field definitions are based on `captured_data_schema.yaml`.

Key conventions:

- `trajectory_metadata.total_frames` defines the sequence length `T`
- All sequence fields must have the same `T` dimension
- All rotations are represented in axis-angle format
- All positions are measured in meters

## MANO Trajectory Fields

MANO-related data is split into metadata fields and time-series fields.

### Metadata

The following fields in `trajectory_metadata` describe the hand layout:

- `hand_names`: variable-length list of hand names
- `mano_hand_shapes`: MANO shape parameters for each hand

Index mapping:

- `hand_names[i]` corresponds to `hands[i]`
- `mano_hand_shapes[i]` corresponds to `hands[i]`

### Time-Series Data

`hands[]` is a variable-length array. Each element represents one hand over the full trajectory.

- `mano_global_pos` `(T, 3)`  
  Global hand position in meters.
- `mano_global_rot_aa` `(T, 3)`  
  Global hand rotation in axis-angle format.
- `mano_hand_pose` `(T, 48)`  
  MANO hand pose parameters.
  - 45 dimensions for 15 joint rotations
  - 3 dimensions for the wrist
- `mano_joint_pos` `(T, 21, 3)`  
  3D positions of 21 MANO hand joints.
- `urdf_dof` `(T, 26)`  
  URDF degree-of-freedom representation.
  - 20 finger DOFs
  - 6 wrist DOFs

In short:

- `mano_global_pos` and `mano_global_rot_aa` describe the global hand pose
- `mano_hand_pose` describes MANO finger and wrist pose parameters
- `mano_joint_pos` provides the derived 3D hand joint positions
- `urdf_dof` provides a robot/control-oriented representation

## Object Fields

Object-related data is stored in `trajectory_metadata.object_names` and `objects[]`.

### Metadata

- `object_names`: variable-length list of object names

Index mapping:

- `object_names[i]` corresponds to `objects[i]`

### Time-Series Data

`objects[]` is a variable-length array. Each element represents one object over the full trajectory.

- `rot_aa` `(T, 3)`  
  Object rotation in axis-angle format.
- `pos` `(T, 3)`  
  Object position in meters.

Therefore, `objects[i]` stores the full pose trajectory of the `i`-th object across all `T` frames.

## Other Common Fields

- `index.uuid`: unique trajectory identifier
- `index.seed_uuid`: same as `uuid` for captured data; source trajectory ID for generated data
- `index.file_uuid`: source `session_data_files.file_uuid`
- `index.capMachine`: capture machine identifier
- `index.operator`: operator who captured or generated the data
- `index.scene`: scene identifier
- `index.is_generated`: whether the row is generated data
- `timestamp`: per-frame timestamps
- `atomic_actions`: atomic action intervals, such as grasp or release

## Directory Layout

- `Dexcanvas.lance/`: Lance dataset root
- `Dexcanvas.lance/data/`: physical Lance data fragments
- `Dexcanvas.lance/_versions/`: dataset version manifests
- `Dexcanvas.lance/_transactions/`: transaction records
- `Dexcanvas.lance/_latest.manifest`: latest dataset manifest
- `captured_data_schema.yaml`: YAML schema converted from the upstream JSONC schema

## Notes

When adding new fields, keep them consistent with `captured_data_schema.yaml`, especially:

- The shared `T` dimension for sequence fields
- The index mapping between `hands[]` and `trajectory_metadata.hand_names`
- The index mapping between `objects[]` and `trajectory_metadata.object_names`
- Axis-angle rotation representation