At GRIS, we develop new techniques for 3D modeling and rendering, ranging from sketch-based modeling of parameterized models to the rendering of high polygon 3D objects with automatic on-the-fly simplification. 3D modeling techniques are able to highly accelerate and simplify the modeling of complex 3D polygon meshes. Furthermore, complex implicit 3D object representations can directly be modeled with elaborated modeling techniques. The rendering of 3D objects is fully dependent on the object and the purpose. Therefore, special rendering techniques are needed for 3D objects with high polygon counts, or 3D objects represented by complex implicit representations.