<graphics> Andy, Charles, Ian's System.
A geometric engine that most CAD packages now use. ACIS uses a sophisticated object-oriented approach for modelling, the data is stored in boundary representation. Acis is owned by Spatial Technologies.
[How does this differ from "solid modelling"?].
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Nearby terms: ACF/NCP « ACIA « ACID « ACIS » ACK » ACL » ACM