docs/primitive_collision_proxy_spec.md

# Primitive Collision Proxy Storage Specification

Primitive collision proxies are derived assets. They are intended for thin rods, racks, grids, shelves, and slot-like structures where coarse convex decomposition can close functional gaps and very fine convex decomposition can create too many mesh collisions.

Do not overwrite raw meshes or upstream XML files.

## Path layout

Store primitive proxy results under:

```text
assets/<source>/derived/primitive_collision_proxies/<category>/<asset_id>/
```

Example for a RoboCasa dishwasher rack:

```text
assets/robocasa/derived/primitive_collision_proxies/dishwashers/Dishwasher031_rack1_primitive_boxes_v1/
├── metadata.yaml
├── source_refs.yaml
├── README.md
├── REPORT.md
├── proxy/
│   └── primitive_collision_proxy.json
├── mjcf/
│   ├── primitive_geoms_include.xml
│   └── primitive_collision_include.xml
├── curobo/
│   └── primitive_world.yml
└── logs/
    ├── cuboids_summary.csv
    └── proxy_generation.json
```

## When to use this instead of convex decomposition

Use primitive proxies when the collision model must preserve gaps or slots:

- dishwasher racks
- wire baskets
- grilles
- thin support rods
- slot separators

For block-like meshes such as doors, panels, shells, and drawer fronts, prefer CoACD convex decomposition:

```text
docs/convex_decomposition_spec.md
```

## Source of truth

The canonical generated representation is:

```text
proxy/primitive_collision_proxy.json
```

MuJoCo and cuRobo exports are generated from the same proxy JSON:

```text
mjcf/primitive_geoms_include.xml
curobo/primitive_world.yml
```

This is important because simulation and planning should use the same collision approximation whenever possible.

## Run primitive proxy generation

Basic command:

```bash
python scripts/run_primitive_collision_proxy.py \
  assets/robocasa/raw/fixtures/dishwashers/Dishwasher031 \
  --mesh visuals/rack1.obj \
  --variant rack1_primitive_boxes_v1
```

Register a production-ready derived output in the manifest:

```bash
python scripts/run_primitive_collision_proxy.py \
  assets/robocasa/raw/fixtures/dishwashers/Dishwasher031 \
  --mesh visuals/rack1.obj \
  --variant rack1_primitive_boxes_v1 \
  --register-manifest
```

Do not use `--register-manifest` for temporary inspection runs.

## Full script usage

Print current CLI help:

```bash
python scripts/run_primitive_collision_proxy.py --help
```

General form:

```bash
python scripts/run_primitive_collision_proxy.py <raw_asset_dir> \
  --mesh <mesh_path_relative_to_raw_asset_dir> \
  --variant <variant_name> \
  [proxy options] \
  [MJCF options] \
  [repository options]
```

### Required argument

| Argument | Meaning |
| --- | --- |
| `raw_asset_dir` | Raw asset directory under `assets/<source>/raw/<asset_type>/<category>/<asset_id>/`. |

### Input selection

| Option | Default | Meaning |
| --- | --- | --- |
| `--mesh <path>` | none | OBJ mesh to convert to primitive boxes. Path can be relative to `raw_asset_dir` or absolute. Repeat this option for multiple meshes. |
| `--mesh-glob <glob>` | `visuals/rack1.obj` | Glob used when `--mesh` is omitted. Repeatable. |

The script currently parses OBJ geometry directly. Use OBJ input for this tool.

### Repository/output options

| Option | Default | Meaning |
| --- | --- | --- |
| `--variant <name>` | `primitive_boxes_v1` | Output suffix. The derived asset directory becomes `<source_asset_id>_<variant>`. |
| `--output-dir <path>` | canonical derived path | Optional explicit output directory for inspection. Do not use with `--register-manifest`. |
| `--overwrite` | false | Allow writing into an existing output directory. Use cautiously. |
| `--register-manifest` | false | Append the generated derived asset to `manifest/assets.jsonl`. Use only for outputs intended to be kept. |

Compatibility rule:

- Registered assets must use the canonical path under `assets/<source>/derived/primitive_collision_proxies/<category>/<asset_id>/`.
- `--output-dir` is for temporary inspection only and is rejected when combined with `--register-manifest`.

### Proxy generation options

| Option | Default | Meaning |
| --- | --- | --- |
| `--name-prefix <prefix>` | `proxy` | Prefix for generated cuboid and MuJoCo geom names. |
| `--segment-length <float>` | `0.03` | Maximum segment length before splitting a connected component along its longest axis. Smaller values produce more/shorter boxes. |
| `--padding <float>` | `0.001` | Extra half-extent added to each generated cuboid. Larger values make collision more conservative. |
| `--min-half-extent <float>` | `0.0015` | Minimum half-extent per cuboid axis. Prevents zero-thickness boxes. |
| `--min-component-vertices <int>` | `4` | Discard connected components with fewer vertices. |
| `--min-segment-vertices <int>` | `2` | Discard split segments with fewer vertices. |
| `--allowed-contact-target X Y Z` | none | OBJ-local point used to mark nearby cuboids as allowed-contact. |
| `--allowed-contact-radius <float>` | `0.03` | Radius around allowed-contact target. Cuboids whose centers are inside this radius are marked as `allowed_contact`. |

The generated proxy categories are:

```text
forbidden          # exported to MuJoCo and cuRobo
allowed_contact    # exported to MuJoCo for review, omitted from cuRobo forbidden world
```

Use allowed-contact marking for task-specific regions where contact is expected or permitted. Do not treat it as a full physical validation.

### MJCF options

| Option | Default | Meaning |
| --- | --- | --- |
| `--class-name <name>` | `primitive_collision` | `class` attribute for generated `<geom>` entries. Empty string disables it. |
| `--rgba-forbidden "r g b a"` | `0.8 0.1 0.1 0.45` | RGBA for forbidden cuboids. |
| `--rgba-allowed "r g b a"` | `0.1 0.6 1 0.45` | RGBA for allowed-contact cuboids. |
| `--group <int>` | `0` | MuJoCo geom group. Empty string disables it. |
| `--contype <int>` | empty | MuJoCo contact type. Empty means use MuJoCo default. |
| `--conaffinity <int>` | empty | MuJoCo contact affinity. Empty means use MuJoCo default. |

Generated MJCF files:

```text
mjcf/primitive_geoms_include.xml       # include inside the target body
mjcf/primitive_collision_include.xml   # standalone wrapper for preview/convenience
mjcf/preview_world.xml                 # MuJoCo preview scene with raw visual mesh + collision boxes
```

Recommended integration:

```xml
<!-- inside the object body that should receive primitive collision geoms -->
<include file="path/to/mjcf/primitive_geoms_include.xml"/>
```

For visual debugging in MuJoCo, open:

```text
mjcf/preview_world.xml
```

This preview keeps the original visual mesh in gray and the primitive boxes in red.
By default, the red collision boxes are hidden. Press `C` in `scripts/open_mujoco_preview.py` to toggle them on and off.

## Output files

### `proxy/primitive_collision_proxy.json`

Contains:

- format marker
- generation params
- source mesh stats
- cuboid list
- each cuboid's name, source mesh, category, position, half-size, full dimensions, component index, and segment index

### `logs/cuboids_summary.csv`

Tabular summary for inspection:

```text
name
source_mesh
category
component
segment
pos_x / pos_y / pos_z
size_x / size_y / size_z       # MuJoCo half-size
dim_x / dim_y / dim_z          # full dimensions
```

Use this file to identify boxes that are too long, too thick, or unexpectedly spanning a slot.

### `curobo/primitive_world.yml`

cuRobo cuboid fragment generated from `forbidden` cuboids only. `allowed_contact` cuboids are intentionally omitted.

### `REPORT.md`

Human-readable generation report with mesh stats, cuboid counts, largest cuboids, and a review checklist.

## Practical presets

Dishwasher rack first pass:

```bash
python scripts/run_primitive_collision_proxy.py \
  assets/robocasa/raw/fixtures/dishwashers/Dishwasher031 \
  --mesh visuals/rack1.obj \
  --variant rack1_primitive_boxes_v1 \
  --segment-length 0.03 \
  --padding 0.001 \
  --min-half-extent 0.0015
```

Finer boxes:

```bash
python scripts/run_primitive_collision_proxy.py <raw_asset_dir> \
  --mesh visuals/rack1.obj \
  --variant rack1_primitive_boxes_fine_v1 \
  --segment-length 0.015 \
  --padding 0.0005 \
  --min-half-extent 0.001
```

Coarser boxes:

```bash
python scripts/run_primitive_collision_proxy.py <raw_asset_dir> \
  --mesh visuals/rack1.obj \
  --variant rack1_primitive_boxes_coarse_v1 \
  --segment-length 0.06 \
  --padding 0.0015 \
  --min-half-extent 0.002
```

## Review checklist

Before registering primitive proxies in `manifest/assets.jsonl`:

- Open or render `mjcf/primitive_geoms_include.xml` with the visual mesh.
- Confirm boxes do not bridge functional rack slots.
- Confirm boxes are not much thicker than the intended rod/wire collision margin.
- Confirm the chosen `segment-length` is not creating too many boxes for MuJoCo or cuRobo.
- Confirm allowed-contact cuboids, if used, are task-specific and documented.
- Run:

```bash
python scripts/validate_asset.py assets/<source>/derived/primitive_collision_proxies/<category>/<asset_id>
python scripts/validate_asset.py --all
```

## Manifest rule

Primitive proxy results are real derived assets and must be indexed in:

```text
manifest/assets.jsonl
```

Only register reviewed outputs that should be reused. Temporary trials should not be listed in the manifest.