Proxy Builder

Overview

Proxy Builder is a tool for splitting a character model into per-bone pieces and assembling proxy geometry that follows each bone. It is used for creating simplified geometry for layout rigs and game engines.

How to Launch

Launch the tool from the dedicated menu or using the following command:

import faketools.tools.rig.proxy_builder.ui
faketools.tools.rig.proxy_builder.ui.show_ui()

Workflow

The expected basic workflow is as follows:

1. Cutting the model — Split the mesh into per-bone pieces using weight boundaries or cutter planes
2. Assigning pieces to bones — Assign each piece to a bone, generating groups with parentConstraints
3. Finalizing the model — Combine geometry within per-bone groups into the final form

1. Cutting the Model

Split the mesh into per-bone pieces using weight boundaries or cutter planes.

1. Activate the Cut tab in the tool.

2. Register the model(s) to cut in Source Meshes.

3. In Cut Method, choose whether to cut by weight boundaries (By Weights) or by cutter planes (By Planes).

   • By Weights: Cuts the mesh at skin weight boundaries. Only works when the meshes registered in Source Meshes have skin weights assigned.
   • By Planes: Cuts the model using cutter planes (mesh or NURBS surface). Cutter planes can also be created from the Plane tab.

4. Click the Cut button to cut the model. The cut pieces are generated under piece_grp.
   To work on a duplicate of the model, enable the Keep Original Mesh checkbox before clicking Cut.

   

2. Assigning Pieces to Bones

Assign each piece to a bone, generating groups with parentConstraints.
The purpose is to verify that each piece has been correctly cut to correspond to its skeleton.

1. Activate the Assign tab in the tool.

2. List the cut pieces in the upper list. You can bulk-load pieces from the group set in Piece Group using Load.

3. Next, configure how to distribute the cut pieces to each skeleton. Select the method from Assign Method.

   • By Weights: Distributes pieces based on the skin weight coverage of the geometry set in Reference Mesh.
   • By Bones: Distributes pieces based on the distance between each geometry and the bone segments.

4. Register the target bones in the Joints list. Required for By Bones. For By Weights, if the list is empty, bones are automatically determined from the skinCluster node.

5. Click the Assign & Create Groups button. Each piece is grouped per bone.

   

3. Finalizing the Model

Combine geometry within per-bone groups into the final form.

1. Activate the Finalize tab in the tool.

2. Set the groups generated by the Assign tab (proxy_grp) in Source Group and click Load.

3. Select the combine method for each bone’s geometry from Combine Mode.

   • Single Mesh per Joint: Combines pieces into a single mesh as-is.
   • Per Shader (shape parent): Combines only pieces with the same shader, then parents the separate shader shapes under a single transform.
   • Per Shader (shape parent) will produce an error if multiple shaders are assigned within the same shell.

4. Click the Finalize button to generate the combined models.

   

Plane Tab

A helper tool for creating and mirroring cutter planes used with the By Planes option in the Cut tab.

Create Plane at Joint

Creates a cutter plane at a joint’s position.
The plane name is automatically generated from the joint name (e.g., LeftArm_cut_plane).

Configure the options, select the joint(s) where you want to create cut planes (multiple selection supported), and execute Create Plane.

Basic Settings

• Target Mesh: Select a reference mesh for automatic size calculation and click Set (optional). After setting, use ON/OFF to toggle whether to reference it.

Plane Type

For polygons, cutting occurs per face, so use the lowest resolution polygon possible. Polygons with more than 5 faces will produce an error.

Axis

Select the reference axis for the plane’s normal direction (X / Y / Z).

Rotation Mode

Select how the plane’s rotation (normal direction) is determined.

Aim Target (when Rotation Mode is Aim)

• Aim Joint: Explicitly specify a target joint for aiming (optional). When set, the Aim Target selection is ignored.

When searching for child joints, those with the io (intermediateObject) attribute set to True are excluded.

Size Scale

When Target Mesh is set, automatic size calculation via raycasting is performed. Size Scale is a multiplier applied to the result.

Mirror Plane

Mirrors the selected plane(s) along the specified axis. The mirrored name is automatically generated based on left/right patterns (from shared config mirror_patterns).

• Mirror Axis: Axis to mirror along (X / Y / Z)
• Select the plane(s) and click Mirror

Design Principles

• Framework-independent: Uses only standard Maya operations. Does not depend on any specific rig framework’s API or naming conventions
• Verifiable between steps: Results of each step can be reviewed and adjusted before proceeding to the next
• Loosely coupled steps: Minimizes dependencies between steps, allowing you to start from any step
• Binding without tool API dependency: The relationship between bones and geometry is readable from the scene structure (naming + parentConstraint)