Samuel created this short particle animation using 'curl fields' - a way to calculate the rotation of vectors around a point, a way to simulate particles sliding off a virtual 3D landscape. If that sounds very mathematical - it is! He provides an in-depth overview of the process on Blender Artists. https://blenderartists.org/uploads/default/original/4X/8/5/6/8564d94fa554a19416f6615291f7225800d93ab3.mp4Source