This paper investigates the integration of mixed reality with parametric modelling. This supports the concept of Form Fostering, which goes beyond the traditional form finding. Form Fostering takes sensory input from the physical world to inform a parametric model. We will present a prototype of the system that we have developed, which includes the use of a Wii Remote, an Arduino processing board, servo actuators and a camera as haptic input and interaction devices for Form Fostering. The potential benefits of designing in mixed reality are significant since designers can get real-time feedback from both the physical context and from changing physical design constraints represented by virtual parametric relationships. In order to leverage seamless interaction and activity between the physical and the virtual world, it is invaluable to consider sensing as an input for design.