# Convex Decomposition Storage Specification Convex decomposition outputs are derived assets. They must not overwrite raw meshes or upstream XML files. ## Path layout Store convex decomposition results under: ```text assets//derived/convex_decompositions/// ``` Example for a RoboCasa dishwasher: ```text assets/robocasa/derived/convex_decompositions/dishwashers/Dishwasher031_vhacd_v1/ ├── metadata.yaml ├── source_refs.yaml ├── meshes/ │ ├── door/ │ │ ├── part_000.obj │ │ ├── part_001.obj │ │ └── ... │ ├── rack0/ │ └── rack1/ ├── mjcf/ │ ├── convex_assets_include.xml │ ├── convex_geoms_include.xml │ └── convex_collision_include.xml └── logs/ └── decomposition.json ``` Example for a DISCOVERSE object: ```text assets/discoverse/derived/convex_decompositions/objects/cup_vhacd_v1/ ├── metadata.yaml ├── source_refs.yaml ├── meshes/ │ └── cup/ │ ├── part_000.obj │ └── part_001.obj ├── mjcf/ │ ├── convex_assets_include.xml │ ├── convex_geoms_include.xml │ └── convex_collision_include.xml └── logs/ └── decomposition.json ``` ## Required files ### Scaffold command Use the helper script to create the derived asset skeleton: ```bash python scripts/scaffold_convex_decomposition.py assets/robocasa/raw/fixtures/dishwashers/Dishwasher031 ``` This creates a new directory under `assets/robocasa/derived/convex_decompositions/...` with placeholder metadata, source references, logs, and MJCF include files. Fill in the generated meshes and replace placeholders before adding the asset to `manifest/assets.jsonl`. ### Run CoACD decomposition Use `scripts/run_convex_decomposition.py` when you want to actually generate convex parts and MuJoCo include files: ```bash pip install trimesh coacd python scripts/run_convex_decomposition.py \ assets/robocasa/raw/fixtures/dishwashers/Dishwasher031 \ --mesh visuals/door.obj \ --mesh visuals/rack0.obj \ --variant coacd_v1 \ --register-manifest ``` If `--mesh` is omitted, the script searches common mesh locations under the raw asset directory: ```text visuals/*.obj visuals/*.stl meshes/*.obj meshes/*.stl ``` The script writes generated pieces to `meshes//part_000.obj`, records hashes and parameters in `logs/decomposition.json`, and creates MJCF include files under `mjcf/`. For each generated convex part, the script also records size and complexity statistics in both `logs/decomposition.json` and `logs/parts_summary.csv`: ```text bbox_extents # x/y/z axis-aligned bounding-box dimensions bbox_center # axis-aligned bounding-box center bbox_volume mesh_volume surface_area num_vertices num_faces ``` Use `logs/parts_summary.csv` to find parts that are too small, too large, or unexpectedly complex before using them as collision geometry. ### Decomposition granularity controls CoACD does not directly support a target physical bbox size such as "each part should be about 5 cm". Part size is controlled indirectly through decomposition granularity parameters: ```text --threshold Lower value -> stricter convex approximation -> usually more/smaller parts. --max-convex-hull Caps the number of convex hulls. Lower cap -> fewer/larger parts. --no-merge Disables hull merge. Usually keeps more/smaller parts. --mcts-max-depth Higher value allows deeper recursive splitting. --mcts-nodes --mcts-iterations More search can find finer/better splits, with higher runtime. --preprocess-resolution --resolution Higher values preserve more geometric detail before decomposition. --max-ch-vertex Controls complexity of each convex hull, not physical size directly. ``` Practical presets: ```bash # Coarser collision: fewer/larger parts, faster simulation python scripts/run_convex_decomposition.py \ --mesh \ --threshold 0.08 \ --max-convex-hull 8 # Finer collision: more/smaller parts, more accurate but heavier python scripts/run_convex_decomposition.py \ --mesh \ --threshold 0.02 \ --max-convex-hull 32 \ --no-merge \ --mcts-max-depth 4 ``` After generation, inspect `logs/parts_summary.csv` to decide whether the resulting part sizes are acceptable for the target task. ## Full script usage Print the current CLI help: ```bash python scripts/run_convex_decomposition.py --help ``` General form: ```bash python scripts/run_convex_decomposition.py \ --mesh \ --variant \ [CoACD options] \ [MJCF options] \ [repository options] ``` ### Required argument | Argument | Meaning | | --- | --- | | `raw_asset_dir` | Raw asset directory under `assets//raw////`. | ### Input selection | Option | Default | Meaning | | --- | --- | --- | | `--mesh ` | none | Mesh to decompose. Path can be relative to `raw_asset_dir` or absolute. Repeat this option for multiple meshes. | | `--mesh-glob ` | `visuals/*.obj`, `visuals/*.stl`, `meshes/*.obj`, `meshes/*.stl` | Glob used when `--mesh` is omitted. Repeatable. | Example: ```bash python scripts/run_convex_decomposition.py \ assets/robocasa/raw/fixtures/dishwashers/Dishwasher031 \ --mesh visuals/door.obj \ --mesh visuals/rack0.obj \ --mesh visuals/rack1.obj ``` ### Repository/output options | Option | Default | Meaning | | --- | --- | --- | | `--variant ` | `coacd_v1` | Output suffix. The derived asset directory becomes `_`. | | `--overwrite` | false | Allow writing into an existing derived output directory. Use cautiously. | | `--register-manifest` | false | Append the generated derived asset to `manifest/assets.jsonl`. Use only for outputs you intend to keep. | Output path: ```text assets//derived/convex_decompositions//_/ ``` ### MJCF options | Option | Default | Meaning | | --- | --- | --- | | `--class-name ` | `convex_collision` | `class` attribute for generated `` entries. Empty string disables it. | | `--rgba "r g b a"` | `0.8 0.2 0.2 0.35` | RGBA for generated collision geoms. | | `--group ` | `0` | MuJoCo geom group. Empty string disables it. | | `--contype ` | empty | MuJoCo contact type. Empty means use MuJoCo default. | | `--conaffinity ` | empty | MuJoCo contact affinity. Empty means use MuJoCo default. | Generated MJCF files: ```text mjcf/convex_assets_include.xml # include at MJCF root/top level mjcf/convex_geoms_include.xml # include inside the target body mjcf/convex_collision_include.xml # standalone wrapper for preview/convenience ``` ### CoACD granularity and quality options | Option | Default | Effect | | --- | --- | --- | | `--threshold ` | `0.05` | Main concavity threshold. Lower values usually create more/smaller and more accurate parts. Higher values create fewer/coarser parts. | | `--max-convex-hull ` | `-1` | Maximum hull count. `-1` means CoACD default/unlimited. Lower cap forces fewer/larger parts. | | `--no-merge` | false | Disable CoACD hull merge. Usually preserves more/smaller parts. Useful for wire/rack-like geometry, but may create many parts. | | `--mcts-max-depth ` | `3` | Maximum recursive split depth. Higher values can produce finer decomposition and longer runtime. | | `--mcts-nodes ` | `20` | Search nodes per MCTS step. Higher values can improve split search and increase runtime. | | `--mcts-iterations ` | `150` | MCTS iterations. Higher values can improve split quality and increase runtime. | | `--resolution ` | `2000` | CoACD sampling/resolution parameter. Higher values preserve more detail and cost more time. | | `--preprocess-mode {auto,on,off}` | `auto` | Whether CoACD preprocesses the input mesh. | | `--preprocess-resolution ` | `50` | Resolution for preprocessing. Higher values may preserve more detail and cost more time. | | `--max-ch-vertex ` | `256` | Maximum vertices per convex hull. Controls hull complexity, not physical part size directly. | | `--pca` | false | Enable CoACD PCA mode. Can affect orientation/splitting behavior. | | `--decimate` | false | Enable CoACD decimation. May simplify output. | | `--extrude` | false | Enable CoACD extrusion. | | `--extrude-margin ` | `0.01` | Margin used when extrusion is enabled. | | `--apx-mode {ch,box}` | `ch` | Approximation mode: convex hull or box approximation. | | `--real-metric` | false | Enable CoACD `real_metric` option if supported. | | `--seed ` | `0` | Random seed for reproducible runs where CoACD supports it. | ### Practical parameter presets Block-like assets such as doors, panels, and shells: ```bash python scripts/run_convex_decomposition.py \ --mesh visuals/door.obj \ --variant coacd_v1 \ --threshold 0.05 \ --max-convex-hull 16 ``` Coarser and faster collision: ```bash python scripts/run_convex_decomposition.py \ --mesh \ --variant coacd_coarse_v1 \ --threshold 0.08 \ --max-convex-hull 8 ``` Finer collision: ```bash python scripts/run_convex_decomposition.py \ --mesh \ --variant coacd_fine_v1 \ --threshold 0.02 \ --max-convex-hull 32 \ --no-merge \ --mcts-max-depth 4 ``` Rack/wire-like assets such as dishwasher racks: ```bash python scripts/run_convex_decomposition.py \ --mesh visuals/rack1.obj \ --variant rack1_coacd_trial \ --threshold 0.02 \ --max-convex-hull 128 \ --no-merge \ --resolution 2000 \ --mcts-max-depth 4 ``` For rack/wire-like assets, inspect `logs/parts_summary.csv` and visualize the result before registering it. A valid result should not have convex hulls that bridge functional slots or gaps. If the decomposition needs hundreds of parts, primitive collision using capsules/boxes is usually a better engineering choice. ### `metadata.yaml` Minimum fields: ```yaml asset_id: robocasa.convex_decompositions.dishwashers.Dishwasher031_vhacd_v1 source: robocasa asset_type: convex_decompositions category: dishwashers source_asset_id: Dishwasher031 format: obj_mjcf_include entry_file: mjcf/convex_collision_include.xml license: CC-BY-4.0 origin_url: https://robocasa.ai path: assets/robocasa/derived/convex_decompositions/dishwashers/Dishwasher031_vhacd_v1 storage_mode: derived derived_from: - assets/robocasa/raw/fixtures/dishwashers/Dishwasher031 derivation_method: convex_decomposition decomposition_tool: vhacd decomposition_version: TBD decomposition_params_file: logs/decomposition.json validation_status: pending tags: - robocasa - convex_decomposition - collision - mujoco ``` ### `source_refs.yaml` Record exact source files: ```yaml raw_asset: assets/robocasa/raw/fixtures/dishwashers/Dishwasher031 raw_entry_file: assets/robocasa/raw/fixtures/dishwashers/Dishwasher031/model.xml raw_meshes: - assets/robocasa/raw/fixtures/dishwashers/Dishwasher031/visuals/door.obj - assets/robocasa/raw/fixtures/dishwashers/Dishwasher031/visuals/rack0.obj ``` ### `logs/decomposition.json` Record tool parameters and hashes: ```json { "tool": "vhacd", "tool_version": "TBD", "created_at": "YYYY-MM-DD", "params": {}, "inputs": [ { "path": "assets/robocasa/raw/fixtures/dishwashers/Dishwasher031/visuals/door.obj", "sha256": "TBD" } ], "outputs": [ { "path": "meshes/door/part_000.obj", "sha256": "TBD" } ] } ``` ## MJCF integration rule Do not edit raw `model.xml` in place. If MuJoCo collision integration is needed, write a generated include file under: ```text mjcf/ ``` Generated MJCF should be split by include context: ```text mjcf/convex_assets_include.xml # include at MJCF root/top level mjcf/convex_geoms_include.xml # include inside the target body mjcf/convex_collision_include.xml # standalone wrapper for preview/convenience ``` Recommended integration pattern: ```xml ``` This split avoids mixing root-level `` declarations with body-level `` declarations. `convex_collision_include.xml` is provided as a convenience wrapper body and should not be used when replacing collision geometry inside an existing body hierarchy. ## Manifest rule Convex decomposition results are real derived assets and must be indexed in: ```text manifest/assets.jsonl ``` Link-only plans or empty placeholders should not be listed in the manifest.