Multiphase fluid test with tweaked SPH

Here's a video showing my improvement over the model described in “Particle based viscoelastic fluid simulation“. In the original method, multiphase flow wasn't implemented. A straight implementation of multiphase flow with this method would however lead to artifacts at the interface : a gap would be present, induced by a difference in particle mass (so in density). My modification, inspired by the paper “weakly compressible sph for free surface flows“, annihilate this problem as can be seen in this video showing 2 mixing liquids with the following properties : - liquid 1 (blue) : stiffness 1000, surface tension 50, density 1, linear viscosity 0, quadratic viscosity 10 - liquid 2 (orange) : stiffness 1000, surface tension 50, density 0.8, linear viscosity 10, quadratic viscosity 10 Notice how surface tension tends to gather particles of the same specy, not only at the free surface but also at the interface. The initial model couldn't simulate this phenomenon (