meshy-dev/meshy-dcc-adapters/houdini-vdb

houdini-vdb

Typed VDB (sparse volume) authoring for Houdini's native volume SOPs. This is the volumetric counterpart to houdini-mesh-ops: it covers the OpenVDB family that the existing solver skills only reference indirectly through Pyro.

Tracer-bullet flow

1. create_vdb_node(parent_path="/obj/geo1", vdb_type="from_polygons", source_path="/obj/geo1/box1")
2. create_vdb_node(parent_path="/obj/geo1", vdb_type="smooth", source_path="/obj/geo1/vdbfrompolygons1")
3. combine_vdbs(parent_path="/obj/geo1", source_a_path="...", source_b_path="...")
4. inspect_vdb(node_path="/obj/geo1/vdbcombine1")

Longer pipelines belong to houdini_automation__build_node_chain, which builds and validates an arbitrary node recipe; this package stays focused on the single-op calls an agent needs while iterating.

Parameter policy

The tools create and wire nodes; they do not guess parameter values. SOP parameters vary between Houdini releases, so an override the node does not expose fails the call and rolls back rather than being silently skipped. Pass what you want through parameters and read applied_parameters back.

Common vdbcombine operation values to pass through parameters: sdfunion, sdmintersect, sdfdifference, sdfblend, sum, product, min, max.

Source resolution

Both tools resolve sources through one shared helper: a source must be an existing node in parent_path, and source_b_path may not be supplied without source_path (input 0 must never be left dangling). Cross-network inputs are rejected rather than silently accepted, matching resolve_inputs elsewhere in the adapter.

Honesty contract

• inspect_vdb reports geometry_available=false instead of guessing when the

node exposes no cached geometry.

• volume_names is populated from the vdb_grids intrinsic. Read

volume_names_available to disambiguate: False means the read was not available, while False names with True available means the volume genuinely reports no grids. Never infer emptiness from volume_count=0 alone.

• Creation failures destroy only the nodes owned by the failed request, and

parameter writes are rolled back (values, expressions and animation).