Ice, boundary and "vapor" sites are considered
on hexagonal lattice to make snowflake. Boundary (quasi-liquid)
and diffusive (vapor) masses evolve by discrete dynamics.
Step 1. Vapor Diffusion.
Diffusive mass d evolves by diffusion with
uniform weight on the center site and each of its neighbors.
Diffusion does not take place in the ice region.
Initial diffusive density is ρ.
2. Boundary Freezing Proportion 1 - k of the diffusive mass at each boundary
site becomes boundary mass. That is, for boundary sites
b' = b° + (1-k)d°
d' = kd°.
3. Snowflake Attachment A boundary site with 1 or 2 ice neighbors needs
boundary mass at least 1 to join the crystal.
Site with 3 neighbors needs β boundary mass and
site with more then 3 neighbors joins the crystal automatically.
We can use more simple rule: a boundary site needs
boundary mass at least 1 to join the crystal.
4. Snowflake Melting It is not difficult to add boundary masses evaporation.
