SummaryMy practice of reaction-diffusion model. The reaction-diffusion system is a model to generate pattern of surface of some animals (such as zebra or fish). Nice explanation here: http://www.karlsims.com/rd.html . Calculated sphere world with C program, create OpenSCAD sub program (almost C program does everything).Print SettingsPrinter: Da Vinci 2.0 DuoRafts: YesSupports: YesNotes: To change reaction-diffusion pattern (various parameters of reaction-diffusion, random seed, resolution, # of iteration), edit "rdball2.c", compile and run, redirect output to "rdball-sub.scad". The C program output is OpenSCAD subroutine which draws single polyhedron, so the OpenSCAD main program "rdball.scad" is one-liner. The -inner.stl and -outer.stl file is modified with blender. Draw a sphere with certain radius in the rdball, then cut the rdball i(boolean difference) by the ball for the outer, calculate boolean union with the ball for the inner. I printed out with dual filament 3D printer for for each color.How I Designed ThisThe algorithm is Gray-Scott model on sphere world. The sphere is covered by (almost the same size of) triangles, and each crossings (has 6 or 4 neighbors) has the "u" and "v" values of Gray-Scott model. The Laplacian is calculated on the network (thanks to Dr. Ide, Kanagawa Univ.). The sphere is, actually simulated by inscribing octahedron, projected onto the sphere surface. The shown .stl files are, constant k/f/ru/rv program (rdball2.stl) and k varies depending to the z height (latitude) of the ball (rdball2-vary.stl). Both could be generated by INITK1 and INITK2 value in the C program. The C program knows coords of each node ("points" of polyhedron() in OpenSCAD), relationship between each node ("faces" of polyhedron()), so create OpenSCAD module by the C program, and that's almost everything. :-)