During laser transmission welding of plastics, physical contact between the joint parts is necessary. So far, therefore, this technology has been limited to two-dimensional joint geometries. A new welding process based on contour welding can be used to weld complex parts with three-dimensional weld seams. It makes use of air-floating glass spheres to achieve the necessary contact pressure at the joint This leads to a completely new process freedom and a wider range of applications in automotive engineering and the technical textiles industry.