We present a new approach to 3D scene modeling based on geometric constraints. Contrary to the existing methods, we can quickly obtain 3D scene models that respect the given constraints exactly. Our system can describe a large variety of linear and non-linear constraints in a flexible way. To deal with the constraints, we decided to exploit the properties of the GPDOF algorithm developed in the Constraint Programming community [12]. The approach is based on a dictionary of so-called r-methods, based on theorems of geometry, which can solve a subset of geometric constraints in a very efficient way. GPDOF is used to find, in polynomial-time, a reduced parameterization of a scene, and to decompose the equation system, induced by constraints, into a sequence of r-methods. We have validated our approach in reconstructing, from images, 3D models of buildings based on linear and quadratic geometric constraints.