ActiveSolid is a 3D solid modeling, prototyping, and view mark-up application. It runs in either of two modes: as an Internet Explorer plug-in or as a standalone end-user application. It features an intuitive GUI, import/export plug-in architecture (with free Import/Export plug-ins downloadable from ActiveSolid's home page), associative 3D dimensions, robust Boolean operations on 3D meshes and 2D polygons, 3D slicing, polygon offset, automatic house/roof/wall creation, local vertex/face editing, optimal solid reconstruction from parallel contours, extrude along vector or a polyline path, 2D mark-up tools, and an array of other common 3D object creation tools. Supported file formats include STL, DXF, Q3BSP, XGL and various 2D bitmap formats.
Version 2 adds powerful unlimited undo/redo and voxel modeling capability (using linear octrees), plus a critical fix for the random freeze issue of the Spin tool.