Incomplete!
Based on "A material point method for snow simulation" by A. Stocmakhin et al.
https://github.com/WindQAQ/MPM/blob/master/src/mpm_solver.cu
https://www.seas.upenn.edu/~cffjiang/research/mpmcourse/mpmcourse.pdf
http://alexey.stomakhin.com/research/siggraph2013_tech_report.pdf