OK, extracting the data from an OBJ or STL file and converting to a PBM should not be a great problem, but I am not sure how the PBM data should be arranged in a CSV file. The data in a PBM file is basically a representation of a monochrome raster image arranged in rows and columns of ones and zeros. I can guess how you could place the data for one layer in a CSV, but I would think that there must also be some elevation data added for multiple layers. Do you have an example of the CSV file that would be required to print multiple layers?