📖 Glossary¶

One-line definitions for the terms that appear across the rest of the documentation, grouped by subject and alphabetized within each group.

Scene and Constraints¶

Center mode: How the pivot for a Spin or Scale operation is resolved. One of Centroid (vertex centroid at runtime), Fixed (a user-entered coordinate), Max Towards (centroid of vertices furthest along a direction), or Vertex (a single vertex picked in Edit Mode).
Contact gap: Separation distance the solver enforces between surfaces, specified per group or per collider as an absolute Blender-unit value or as a ratio of the group’s bounding-box diagonal. See Material Parameters.
Cross-stitch anchor: Per-vertex barycentric data recorded during a Snap, tying each source-object vertex to a target triangle so the stitch survives small mesh edits.
Embedded Move: A pin Operation that plays back per-vertex keyframes captured in Blender, letting pinned vertices follow a hand-animated or scripted pose sequence during the solve.
Invisible collider: A parametric wall or sphere that acts as a collision boundary for the simulation without being rendered in Blender. Walls are infinite planes; spheres support invert (inside-surface collision) and hemisphere (bowl shape) flags. See Invisible Colliders.
Merge pair: Two snapped objects registered as a solver stitch constraint, optionally with explicit stitch anchors. Created by the snap operator and stored on the scene. See Snap and Merge.
Object group: One of up to 32 slots on a scene that holds a type (Solid / Shell / Rod / Static), material parameters, assigned meshes, and pins. See Object Groups; Static groups are covered separately in Static Objects.
Operation: A keyframed action stacked on a pin: Move By, Spin, Scale, Torque, or Embedded Move. Torque is exclusive with the first three; it can still coexist with Embedded Move. See Pins and Operations.
Overlay color: Per-group viewport tint that shows which objects belong to which group. Defaults by group type and can be overridden per group.
Pin: A named set of vertices on an object, registered as a simulation constraint target. On meshes this is a regular Blender vertex group; on curve objects (which have no vertex groups) the add-on stores the control-point indices in an internal _pin_<name> custom property on the curve. Stacks operations on top, optionally with pull strength or a pin duration.
Pin duration: A frame limit that releases a pin at a specified frame, handing the affected vertices back to free dynamics mid-simulation.
Pull strength: Soft-force magnitude that replaces a hard pin constraint, pulling vertices toward their target positions rather than holding them rigidly.
Rod: Group type for 1D structures (ropes, wires, threads). Accepts mesh and curve objects.
Shell: Group type for thin deformable surfaces (cloth, fabric). Accepts mesh objects.
Snap: KDTree-based vertex alignment that translates object A so its nearest vertices land on object B’s nearest vertices. Typically followed by a merge pair registration and, for shell+solid pairs, a stitch stiffness.
Solid: Group type for volumetric deformable bodies.
Static: Group type for non-deforming collision objects (ground planes, props, mannequins). Exposes friction and contact settings; motion is driven by Blender transform keyframes rather than by the solver.
Stitch stiffness: Per-merge-pair compliance value that softens the stitch when a solid is involved. Pure shell-shell and rod-rod pairs merge vertices exactly and do not expose a stiffness slider.
Torque: A pin Operation that applies rotational force around an axis derived from the pinned vertices. Exclusive with Move By, Spin, and Scale; coexists with Embedded Move.
UUID registry: Per-object UUID assignment maintained by the add-on. Keeps group references stable across rename operations so merge pairs, assigned objects, and pin vertex groups survive object renames.

Parameters and Simulation¶

Bake: Converts the live PC2-plus-modifier preview into standard Blender animation: shape keys and fcurves on meshes, or per-control-point keyframes on curves. The baked result renders without the add-on installed. See Baking Animation.
Constitutive model: The mathematical model that governs how a group deforms (for example Baraff-Witkin, Stable NeoHookean, or ARAP). Available choices depend on group type.
Dynamic parameter: A scene-level parameter whose value is keyframed over time: gravity, wind, air density, air friction, or vertex air damp. Uploaded with the rest of the parameters at transfer time and replayed by the solver during the run. See Dynamic Parameters.
Fetch: Downloads per-frame vertex data from the solver and wires it up to each simulated object so the timeline plays back the result.
JupyterLab integration: A first-class path for driving the solver from a notebook on the solver host, including headless runs and parameter sweeps without Blender open. See JupyterLab.
Material parameter: A per-group property that controls deformation, density, stiffness, friction, and contact. The applicable fields depend on the group’s type. See Material Parameters.
Mesh hash: A topology fingerprint (vertex count, face count, UV layout) recorded at transfer time and compared again before Run and Fetch. A mismatch means the Blender mesh no longer matches what the solver has.
PC2: Point Cache 2. The per-frame vertex file format the add-on writes on Fetch (vert_N.bin), read back as the timeline plays. Blender frames 1..N map to remote frames 0..N-1.
Profile: A named preset saved to a TOML file: either a scene profile (scene parameters, dynamic parameters, and invisible colliders) or a material profile (one group’s material parameters). Loaded and saved from the profile dropdown next to the relevant panel.
Resume: Continues a paused or partially completed simulation from the last completed frame, preserving earlier results.
Run: Starts the simulation on the remote solver. Warns on a stale mesh hash and clears prior simulation output before beginning.
Scene parameter: A whole-scene setting (frame range, step size, gravity, wind, air properties, solver tolerances) applied globally rather than per group. See Scene Parameters.
Solver state: The status surfaced by the Solver panel: Connected, Ready, Running, Complete, or Fetched.
Transfer: Uploads geometry, pins, colliders, and every parameter to the solver and rebuilds its scene. Required whenever topology or group membership changes.
Update Params: Re-encodes and uploads parameters without resending geometry, for fast iteration on dynamics and materials.

Connections and Integrations¶

Communicator: The add-on’s single connection manager. It owns all remote operations from a background thread so the UI never blocks on the network.
Connection profile: A saved TOML entry capturing every field of the Connections panel for one host, used to switch between hosts and share presets across a team. See Connection Profiles.
Docker connection: A connection type where the solver runs inside a Docker container on a local Docker daemon. See Docker (Local).
Docker over SSH: A connection type where the solver runs in a container on a Docker daemon reached through SSH, for environments where the administrator hands you a container rather than shell access. See Docker over SSH.
execute_shell_command: MCP tool that runs arbitrary shell commands on the Blender host. Paired with run_python_script as an escape hatch for provisioning and maintenance tasks not yet covered by dedicated tools.
Local connection: A connection type where the solver runs on the same Linux host as Blender, reached over a loopback socket. See Local.
MCP resource: A read-only asset exposed by the MCP server via resources/read, covering live scene snapshots (blender://scene/current) and the bundled llm://<topic> markdown docs.
MCP server: The bundled Model Context Protocol server on localhost:9633 that exposes add-on operations as JSON-RPC tools for external agents. See MCP Server.
MCP tool: A JSON-RPC method exposed by the MCP server and dispatched with tools/call. Goes through the same validation layer as the sidebar buttons.
Protocol 0.02: The current wire protocol version between the add-on and server.py. The server advertises its version on connect; mismatches surface as a protocol-version-mismatch status and refuse to proceed.
Python API (add-on): The zozo_contact_solver module imported from Blender’s text editor or a notebook. Covers the same validation layer as the sidebar and the MCP server. See Blender Python API.
run_python_script: MCP tool that evaluates arbitrary Python inside Blender. Exists for operations the add-on does not yet expose as first-class tools; see the security note in MCP Server.
server.py: The solver process launched on the remote side (or as a local subprocess for Windows Native) that listens for work over TCP on the configured port (default 9090).
Session ID: Per-connection identifier the server assigns at start. Persisted with the .blend on save so a reopened file can detect whether the remote has been reset since the file was saved.
SSH Command mode: A connection backend that parses host, port, username, and key path out of a plain ssh … string. Convenient when the command is pasted from a deployment script but brittle if your real config depends on ~/.ssh/config wildcards.
SSH connection: A connection type where the solver runs on a remote Linux host reached by SSH, with credentials entered as explicit fields. See SSH.
Streamable HTTP: The MCP transport profile (protocol version 2025-06-18) used by the bundled MCP server. All traffic goes through a single /mcp endpoint with a server-assigned Mcp-Session-Id.
Windows Native connection: A connection type where the solver runs directly as a Windows subprocess, using a bundled Python interpreter and no SSH or Docker. See Windows Native.