Auto Character System 3 aims to redefine rigging in Modo
A timelapse video showing the character rig for a spider being assembled in Auto Character System 3. Lukasz Pazera’s long-awaited modular character rigging system for Modo has now been officially released.
Originally posted on 11 December 2020. Scroll down for news of the stable releaase.
The update, which has been touted as a game-changer for character rigging in Modo, turns ACS into a complete modular platform for rigging bipeds, quadrupeds – and creatures with any other number of limbs.
A complete ground-up rewrite of a key tool for Modo character artists
A staple of many Modo character artists’ workflows, ACS occupies a position midway between a conventional third-party add-on and an official Foundry product.
Foundry promoted the previous version of the software – then called Auto Character Setup – on its YouTube channel, and has namechecked ACS3 as one of the tools set to transform rigging in Modo, alongside those being developed by Kitestring, former Pixar TD Rich Hurrey’s online learning platform.
ACS3 is the first update to the software in over five years, and has been in active development for much of that time, eventually entering closed alpha last year.
It’s a complete rewrite of the code – so rigs created in ACS3 are not compatible with those created in ACS2 – and is intended to reinvent the software as a fully customisable modular rigging platform.
Create rigs for characters of all shapes, sizes and limb configurations
Auto Character System 3 makes it possible to create rigs for characters of all shapes and sizes by plugging together readymade modules representing individual body parts.
That includes arms, legs, horizontal and vertical spines, aim at joints, and FK joint chains for tails and tentacles, making it possible to create a wide variety of body plans.
Modules can be extended via Python scripting, making it possible to change their properties dynamically: for example, to change the number of joints used in a spine or tail.
In addition, users can customise rigs to use their own preferred naming conventions and colour schemes.
Streamlined tools for weighting and binding meshes
The software also comes with tools for binding the resulting skeleton to the character mesh.
It supports multiple bind meshes for a single skeleton, and includes tools for binding multiple meshes using a single set of weight maps, and for transferring clothing and props between meshes.
Skin weighting is done through a mix of Modo’s standard tools and custom tools, and is described by Pazera as “wrapping Modo’s native functionality into easier-to-use and more robust versions”.
Time-saving features include options to shift the weights of selected vertices to the average or maximum value for the map, to quantise weights in 0.5% or 1% steps, and to cull weights below a minimum value.
Automatically generates box and mesh proxies to speed up animation workflow
ACS3 supports multiple resolutions, automatically setting up box or mesh proxies to provide better interactive performance than working directly with the hi-res character mesh.
The workflow is non-linear, making it possible to modify a rig after proxies have been generated.
More features currently in development
The initial early access release is still very much a work in progress, with Pazera warning users to “expect unfinished features and bugs”.
Features currently in development include automatic IK/FK blending.
The system will make it possible to pose a character using IK controls, then swich to FK, with ACS automatically transferring pose changes from the IK to the FK rig.
Pazera is also working on a pose library, enabling users to save poses or actions as native Modo presets; tools for keyframe editing; and for exporting to game engines.
Updated 21 November 2022: Auto Character System 3 is now officially available.
Support for Rig Clay lets you animate by manipulating the character mesh directly
Since the initial early access release, several new features have been added to the software, of which one of the biggest is support for the Rig Clay interface, as shown in the video above.
Rig Clay, introduced in Modo 14.2, makes it possible to animate characters more intuitively, by clicking and dragging directly on regions of the mesh, without the need to have rig controllers displayed.
Support for animation retargeting, space switching and twist bones
Other significant changes include support for retargeting, making it possible to transfer animation from characters that use other rig structures – such as those from Adobe’s Mixamo library – to ACS3 rigs.
ACS3 rigs also now support space switching, making it possible to control which other parts of a character’s body a body part inherits motion from, and twist joints, making it possible to pose limbs more realistically.
New Eyes and muscle modules, and new readymade car rig
There is also a new Eyes module for rigging eyeballs and eyelids, including support for corrective morphs, and a new Muscle Joint module, described as a “simple stretchy joint”.
Users also get a readymade car rig for rigging and animating vehicles.
Pipeline integration: near-one-click export to Unity and Unreal Engine, plus Python 3 support
ACS3 also now includes a set of game export tools, integrated into Modo’s native gane export toolbar, making exporting character rigs to Unity and Unreal Engine “pretty much” a one-click process.
In addition, the software mow supports Python 3.9 and 3.7 as well as Python 2.7, in line with the current CY2022 VFX Reference Platform specification.
Pricing and system requirements
Auto Character System 3.0 is available for Modo 14.2+ on Windows and macOS. The Rig Clay interface requires Modo 15.1+. New Personal licences have a MSRP of $99; Studio licences have a MSRP of $299.
Each purchase comes with a separate licence of Auto Character Setup 2, which can also still be bought separately. It is compatible with Modo 801+ and costs $49.