I started by taking a front, side, and top view photo of my face and head and imported the images into Blender in order to make a model of my face. Once I had the basic 3D face model I began to work on the rest of the pieces. I took a photograph of a moon shape that I liked and made a 2D model of it. Once I had this, I took both the 3D face and the 2D moon into FormZ where I turned the moon into a 3D object. I used boolean operations to make the mask have that half shape of a moon, and because the mask follows the shape of my face, I lost the tips of the moon. Again, with boolean operations, I added those parts of the moon back onto the final shape. I did something similar with the small star and the shooting star. Finally, I took the objects into MeshLab to clean them up. For printing purposes, it is crucial that each part of the mask is a solid. This is a simplified version of the work that went into creating this mask, but it is the basic idea behind creating something like this (excluding other technical difficulties one may run into). This mask is composed of 2 pieces; the moon shape, and the shooting star with the little star. These two objects will clip into each other in the future once they are printed.
Note: All images are screenshots of the mask in FormZ