ACIS
ACIS is a 3D boundary-representation (B-rep) geometric modeling kernel, licensed to hundreds of CAD/CAM/CAE products globally. It was developed by Three-Space Ltd (UK), founded by Ian Braid, Alan Grayer and Charles Lang after they left Shape Data, working with Spatial Technology Inc., the Colorado company founded by Dick Sowar. ACIS 1.0 was released in 1989. A popular story says the name stands for "Alan, Charles, Ian's System". Spatial was acquired by Dassault Systèmes in 2000 and still licenses ACIS today. The ACIS source tree was forked twice: first by HP for SolidDesigner (later CoCreate, acquired by PTC and now Creo Elements/Direct), then by Autodesk as ShapeManager, the kernel under Inventor and Fusion 360. Spatial, by then part of Dassault Systèmes, sued Autodesk over the ShapeManager fork, and Autodesk prevailed in 2003.
Why it matters
ACIS and Parasolid together underpin approximately 90% of commercial CAD applications. Understanding which kernel a CAD tool uses explains its interoperability behavior, data translation accuracy, and the geometric capabilities available to developers building PLM integrations. When two CAD files translated through STEP or IGES lose features or change shape, the root cause is almost always a B-rep representation difference between the source and target kernels.
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External References
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Cite this definition
Finocchiaro, Michael. “ACIS.” DemystifyingPLM PLM Glossary, 2026, https://www.demystifyingplm.com/glossary/acis