# Interactive Parametric Design and Robotic Fabrication within Mixed Reality Environment
## 3 Materials and Methods  
In this study, a method for creating parametric design and robotic fabrication steps in a mixed-reality environment is proposed. Users can control parametric design and robotic-fabrication processes with parameters in the mixed-reality environment. Users can also interact physically and virtually with the design and fabrication environment and  
Figure 1: Robotic fabrication workflow in the parametric-design environment [23]. make changes at the time of design and fabrication and all the following steps are updated without the need for user intervention. Users can get real-time design and production feedback in the mixed-reality environment. The robotic-fabrication process can continue with human-robot collaboration. In this way, the whole process from geometric modeling to robotic fabrication can be controlled by hand gestures. Simulation images can be viewed as holographic content by adding on the images of the real production environment. Multiple users can coexist in the same holographic environment at the same time and multiple users can interact with the holographic contents in the same parametric design and robotic-fabrication process. In Figure 2, parametric design and robotic fabrication within a mixed-reality-environment workflow can be seen. The second generation HoloLens mixed-reality device was used in the study. In the HoloLens mixed-reality device, the holographic content is superimposed on top of the real-world images. The mixed-reality device creates holograms of light and sound objects that look like real objects around us. Holograms can respond to the user's gaze, gestures, and voice commands. Holograms are created in a holographic virtual world and on the lens in front of the wearer's eye. The hologram disappears when the angle of view is changed, but if the perspective is directed back to the scene where the object is located, the hologram is displayed again in its real-world location. Users can interact with both real-world objects and the holographic contents in real-time. The mixed-reality device recognizes the boundaries of the real-world environment with its sensors and updates the holographic contents with these boundaries. The mixed-reality device can detect the positions of objects in the real-world, which makes reality perception richer. That user can control holographic content by hand gestures in the mixed-reality environment, strengthens reality perception. In addition, mixed-reality devices allow multiple users to share the same holographic environment and multiple users can interact with the same holographic contents at the same time [26]. In Figure 3, the roles of the mixed-reality tool, the industrial robot, and the parametric-design software in the proposed workflow can be seen. The initial step of the proposed method is to create the parametric-model definition. Grasshopper3d 1.0 software was used as the parametric-design tool in this study. Grasshopper3d parametric-modeling tool runs inside Rhino3d 7.2 modeling software as a plugin. After the model is defined in the parametric-design program, the user can make changes to the parameters of the model in the mixed-reality environment. The user can monitor the changes in the model in the mixed-reality environment while modifying the parameters of the model. Figure 2: Parametric design and robotic fabrication within mixed-reality-environment workflow. After the parametric modeling step, the toolpath that will be used to manufacture the model is calculated with the parametric-modeling tool. The generated toolpath must be post-processed and transformed into robot code in order to be used with the industrial robot. At this point, it is necessary to determine the collision risks that the industrial robot may encounter during production, to detect errors such as accessibility, exceeding axis limits, and singularity, and to avoid collisions and to fix errors. In order to do this, robotic fabrication simulation is created in the mixed-reality environment.