IRIT is a freeform geometric modeling environment that allows one to model general freeform surfaces’ based models as well as polygonal objects, and use Boolean operations on both. Beyond its very strong support for Bezier and B-spline curves and (trimmed) surfaces, IRIT has many unique features that help in handling freeform geometry including strong symbolic, numeric and algebraic based computation and analysis, support of trivariate spline volumes, as well as general multivariate spline functions. IRIT offers numerous unique computational abilities such as extensive bisector computation for curves and surfaces, convex hulls and kernels, freeform curve and surface deformation (including using composition), freeform surface decomposition into piecewise ruled and piecewise developable surfaces, and into adaptive isoparametric curves’ covering, contact and (Hausdorff- and/or extreme-) distance analysis, kinematics analysis over freeforms, wire EDM and multi-axis CNC analysis for freeform surfaces, metamorphosis of curves and surfaces, and artistic line art drawings of parameteric and implicit forms. A rich set of computational geometry tools for freeform splines is offered including basic operations, such as sums and products of splines in arbitrary dimensions, and a powerful spline based non-linear constraints solver. The solver is capable of computing the simultaneous zero sets of arbitrary number of spline multivariates, where the solution space is zero-dimensional, univariates (one-dimensional), or bivariates (two dimensional). The IRIT solid modeler is highly portable across different hardware platforms, including a whole variety of Unix machines, Apple iOS, and Microsoft Windows PC (using a whole variety of VC compilers). It is written in C and currently contains over half a million lines of code.