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Solid models in Alpha_1 are represented by trimmed B-spline (NURBS) sculptured-surface boundary representations. That is, the surfaces of a solid are represented explicitly, and linked together by shared edges. Our NURBS are Non-Uniform knot vector, Rational B-Splines of arbitrary order with tensor-product surfaces trimmed by NURBS curves. Alpha_1, implemented in C++, provides both command-language and graphical, menu-driven interfaces.
An extensive 2D and 3D geometric modeling environment supports user-oriented operations for building up parts from dimensions, through basic geometry (points, lines, arcs, circles, etc.) through curve and surface constructions (profiles, sweeps, extrusions, etc.), shape operations (bend, twist, warp, etc.), and finally solids and boolean expressions (union, intersection, and difference) of solids.
Time-varying models support animation, linkage design, simulations, etc. Volumetric primitives (box, cylinder, sphere, etc.) are represented by "parametric object types" which generate and cache spline-surfaced solid representations on demand. Similarly, mechanical design "features" (holes, pockets, etc.) may be grouped to support automatic CNC machining code generation within a context of machine setups, fixturing, etc. High-level parameterized procedural modeling "power-tools" are easily built up to encapsulate and automate design and manufacturing strategies.
The Alpha_1 software is licensed to our University tech-transfer company, Engineering Geometry Systems (EGS). The only software based on Alpha_1 which is publicly available at this time is the FeatureCam machining product from EGS.