ACIS
| Industry | Software, Computer-aided design (CAD) |
|---|---|
| Predecessor | Three-Space Ltd. |
| Founded | 1985 |
| Founder | Alan Grayer, Charles Lang, Ian Braid, Dick Sowar (founder of Spatial Technology) |
| Headquarters | (not specified) , (not specified) |
| Products | 3D ACIS Modeler |
| Parent | Dassault Systèmes |
The 3D ACIS Modeler (ACIS) represents a geometric modeling kernel created by Spatial Corporation, formerly known as Spatial Technology, which operates under the umbrella of Dassault Systèmes. This kernel serves as the foundational 3D modeling engine for a diverse range of software applications spanning sectors such as computer-aided design, computer-aided manufacturing, computer-aided engineering, architecture, engineering and construction, coordinate-measuring machine operations, 3D animation, and shipbuilding industries. It delivers essential 3D modeling capabilities tailored for software developers and manufacturers alike.
Built upon an object-oriented C++ framework, ACIS supports hybrid modeling by combining wireframe model, surface, and solid modeling techniques. It accommodates both manifold and non-manifold topologies while offering an extensive suite of geometric operations.
History
As a second-generation geometric kernel, ACIS succeeded the initial generation represented by Romulus.
The acronym ACIS is widely interpreted to mean Alan, Charles, Ian's System, honoring founders Alan Grayer, Charles Lang, and Ian Braid from Three-Space Ltd. Alternatively, it is sometimes expanded to Alan, Charles, Ian and Spatial, reflecting the involvement of Spatial Technology. Another perspective incorporates Dick Sowar, founder of Spatial Technology, into the acronym. Additionally, the creators have mentioned a possible inspiration from Greek mythology (see also Acis).
In 1985, Three-Space Ltd. was established in Cambridge, England by Grayer, Lang, and Braid. Shortly thereafter, Spatial Technology—founded by Dick Sowar in 1986—commissioned Three-Space to develop the ACIS kernel for use in its Strata CAM software. The initial release of ACIS occurred in 1989 and was subsequently licensed by HP for integration within its ME CAD software.
After Spatial was acquired by Dassault Systèmes around the year 2000, modifications were made to the ACIS file format, which then ceased to be publicly documented.
Architecture
A software component refers to a specialized functional unit—a set of software elements grouped together to fulfill a particular role within a larger software system or product. Software products are typically composed of one or more components bundled and marketed as complete packages. These components can be combined in multiple configurations to create various products.
The ACIS product suite leverages component-based software technology, allowing applications to include only those components necessary for their specific requirements. For many functionalities, multiple components may be accessible either from Spatial or third-party providers, giving developers flexibility to choose the optimal option based on their platform or application needs. For instance, Spatial supplies several rendering components designed to address different user demands.
Supported Platforms and Operating Systems
| Platform | Operating System | Compiler | 32-bit | 64-bit |
|---|---|---|---|---|
| Microsoft | Windows 7 | Visual C++ 2010, 2013, 2015 | Yes | Yes |
| Microsoft | Windows 8, 8.1, 10 | Visual C++ 2010, 2013, 2015, 2017 | No | Yes |
| Red Hat | Enterprise Linux 5.0, 6.0, 7.0 | GNU C++ gcc 4.1.2 | Yes | Yes |
| Apple | OS X 10.7.5, 10.10 | Clang version 4.1 (64-bit) | No | Yes |
ACIS Modeler
The primary capabilities of ACIS are divided into three key segments:
3D Modeling
- Transform 2D curves into intricate surfaces or solids through extrusion, revolution, and sweeping.
- Create fillets and chamfers along edges and faces.
- Generate surfaces that conform to closed curve frameworks.
- Produce repetitive geometric patterns.
- Create hollow interiors within solids and thicken surface layers.
- Interactively manipulate curves, surfaces, and solids by bending, twisting, stretching, or warping.
- Perform Boolean operations such as intersection, subtraction, and union on curves, surfaces, and solids.
- Construct lofted surfaces from profile curves.
- Modify surfaces by tapering, offsetting, or translating them within the model.
3D Model Management
- Embed custom user data at any hierarchical level of the model.
- Monitor changes in geometry and topology over time.
- Compute physical properties like mass and volume.
- Represent solid subregions through cellular topology modeling.
- Provide unlimited undo and redo capabilities with separate history tracking.
3D Model Visualization
- Convert surface geometries into polygonal mesh tessellations.
- Enhance surfacing techniques using the optional Deformable Modeling module.
- Create accurate 2D projections with hidden line removal functionality via the optional PHL V5 add-on.
- Facilitate the creation of graphical applications.
ACIS Modeler Extensions
- CGM Polyhedra
- This extension integrates polyhedral modeling with boundary representation (B-rep) within the 3D ACIS Modeler. It allows users to incorporate approximate polyhedral data into workflows such as 3D printing, subtractive manufacturing, and analysis by providing familiar interfaces for both existing users and newcomers.
- 3D Deformable Modeling
- A dynamic sculpting tool embedded in Spatial’s 3D modeling suite that supports both local and global modifications of free-form B-spline and NURBS curves and surfaces, thereby increasing design adaptability.
- Advanced Covering
- Initially part of the Deformable Modeling package, this feature is now offered as a separate add-on. It applies algorithms to generate n-sided surfaces that adhere to user-specified boundary tolerances and optional internal guides. This is particularly useful in consumer product design for tasks such as end-capping, correcting post-translations, and defining surfaces from curve inputs.
- Defeaturing
- This automation tool removes minor features from 3D models that are irrelevant for simulation or analysis purposes. It simplifies models used by computer-aided engineering analysts, minimizing manual preparation time and reducing costs associated with meshing.
- CGM HLR
- A hidden line removal solution derived from CATIA V6 technology that requires an ACIS license. Despite the dominance of 3D CAD in engineering workflows, 2D drawings remain critical for technical documentation in manufacturing and architecture. CGM HLR efficiently produces precise 2D views from 3D models by appropriately eliminating or styling obscured edges.
Save File Types
ACIS offers two types of save formats: Standard ACIS Text (SAT) and Standard ACIS Binary (SAB), both containing equivalent data sets.
SAT files are human-readable ASCII text files formatted for clarity, identified by the .sat extension.
SAB files utilize a binary format that is more compact but not readable by humans. They incorporate delimiters and binary tags and carry the .sab file extension.
Save File Composition
The SAT format specification for version 7.0, released around 2001, is publicly accessible, allowing third-party software—including those not utilizing ACIS—to interpret the data within these files. This documentation outlines the file's architecture, data encapsulation methods, entity classifications, subtypes, and referencing mechanisms. It is important to note that more recent ACIS iterations employ a modified SAT format with proprietary specifications, which necessitate either the original ACIS library or reverse engineering techniques to decode contemporary SAT files.
A typical save file consists of the following elements:
- a header spanning three lines
- entity records that comprise the majority of the stored data
- an optional marker indicating the start of historical data
- optional legacy entity records supporting history tracking and rollback functionality
- an optional marker denoting the conclusion of historical data
- a definitive end-of-file marker
Beginning with ACIS Release 6.3, the file header must explicitly include both the product identifier and measurement units prior to saving a SAT file.
ACIS Versions and Corresponding Release Numbers
Spatial oversees the development of ACIS and manages two versioning schemes: the current release number and the save version number. The save version guarantees backward compatibility, ensuring that SAT files remain readable by earlier ACIS releases.
Starting from Release 4.0, changes to the SAT format were confined to major releases only. This approach enabled applications operating on the same major version to exchange data seamlessly without concern for minor version discrepancies. This was accomplished by embedding solely the major version indicator within save files and avoiding increments to minor versions between major updates.
With Release 7.0, ACIS reinstated full version numbering including major, minor, and point (patch) levels. In September 2015 (Release 2016 1.0), Spatial adopted Semantic Versioning principles, combining model year identifiers with major, minor, and point releases within each year.
Overview of how releases impact SAT files:
- Major release: Potential modifications to SAT file structure; introduces significant new features; may necessitate considerable adjustments in dependent applications
- Minor release: No alterations to SAT files; introduces additional functionality; minimal application updates might be required
- Point release: Focused on bug corrections and service packs only
| Release | Date |
|---|---|
| 2020 1.0 | 2019.Nov.12 |
| 2019 1.0 | 2018.Nov.13 |
| 2018 1.0 | 2017.July.26 |
| 2017 1.0 | July 2016 |
| 2016 1.0 | September 2015 |
| R25 | July 2014 |
| R24 | June 2013 |
| R23 | August 2012 |
| R22 | July 2011 |
| R21 | May 2010 |
| R20 | May 2009 |
| R19 | July 2008 |
| R18 | November 2007 |
| R17 | April 2007 |
| R16 | January 2006 |
Industry Adoption
As of 2023, several CAD platforms including Alibre Design, BricsCAD, SpaceClaim, TurboCAD, Cimatron, Viacad, SharkCad, and Vertex have integrated ACIS as their core geometric modeling kernel.