Originally posted on 11 December 2020. Scroll down for updates.
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”.
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.
By the time of the stable release, ACS3 should have “most of” the same features as ACS2, plus those made possible by the new architcture, although retargeting and corrective morphs are not currently planned.
Updated 18 January 2020: Lukasz Pazera has released Build 10 of ACS3.
The update adds two new features: a readymade car rig for vehicle animation, shown in the video above, and the option to bake ACS3 rigs for export to external apps like Unity and Unreal Engine.
Pricing and system requirements
Auto Character System 3 is available for Modo 14.2 on Windows and macOS in early access. Pazera aims to release new builds every four to six weeks, with the stable release “some time in 2021”.
New licences cost $299, although the software is available at a launch discount. Each purchase comes with a separate licence of Auto Character Setup 2, which can also still be bought separately.
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