Dynamic Hourglass

[Steve Bentley]

For sand don’t use a sphere – too many polys to figure out. You can use either a pyramid shape (4 sided included base) or a platonic with 5 or 6 sides or a flat square that always faces camera. Platonics are nice because they are slightly asymmetrical so they don’t end up looking like a lot of triangles or squares and because of their shape they will hook together like sand does.
You can also tell the dynamics collision engine to use a simpler “stunt” shape (like a single vertex poly) to determine when things run into each other. This reduces the time needed to calculate the physics.

And most of all don’t use a sphere that hasn’t been collapsed to be editable. If you use a perfect sphere (the primitive from C4D) it has in theory infinite polys because it will always render smooth no matter how close you get. On top of that, because its not polys the physics engine has trouble calculating when one poly hits another.

Better still you could use a particle system that just impacts on the glass itself and not on other sand particles. If you get enough of them going it acts like a fluid as is flows and you don’t notice that they aren’t bouncing off each other and just bouncing off the glass.
Don’t just rely on the geometry of the glass to create that pinch point at the apex. Use a force node to slow them down as they pass through, either with friction or with a physics time function.