Sand may seem simple, but scientists still have a lot to learn about how billions of tiny grains behave together.
Now, researchers have found that focusing on one surprisingly important feature—the shape of individual grains—could make computer simulations of sand faster and more realistic.
The research, led by scientists at the Institute of Science and Technology Austria (ISTA), could improve digital simulations of everything from sand dunes and beaches to avalanches and rockslides.
It could also help visual effects artists create more convincing landscapes for movies and games.
Simulating sand is extremely difficult because every grain has its own size, shape and position. Each grain can also collide, slide, roll or become stuck against its neighbors. Calculating all these interactions for millions or billions of grains requires enormous computing power.
The problem becomes obvious in large movie scenes. For example, filmmakers working on the 2013 movie The Hobbit: The Desolation of Smaug needed to create scenes involving huge piles of gold coins surrounding the dragon Smaug.
Simulating billions of individual coins was impractical, so the visual effects team reportedly used about 40,000 physical prop coins to help reproduce their movement digitally.
Real sand can be even more complicated because natural grains are rarely smooth or identical.
Instead of trying to reproduce every tiny bump and edge, the ISTA researchers asked whether simplified grain shapes could capture the overall behavior of different kinds of sand.
They tested several shapes, ranging from simple spheres to unusual grains with multiple branches or “fangs.” Their findings were published in ACM Transactions on Graphics and presented at SIGGRAPH Asia 2025.
Smooth spherical grains behaved much as expected, easily rolling and sliding past one another. At the other extreme were shapes the researchers called “dodecafangs,” which have 12 fang-like extensions.
These grains became strongly tangled together. A sandcastle made from them would be remarkably difficult to destroy. Instead of crumbling like ordinary sand when struck, the material could behave more like a continuous elastic solid.
Other shapes produced different effects. The researchers tested grains called “dolosse,” inspired by large concrete structures used to protect coastlines from waves. Despite their complicated shape, these grains did not strongly lock together and could still slide past one another relatively easily.
Perhaps the most surprising results came from six-legged grains called “hexapods.” When a cup filled with these grains was turned upside down, the resulting pile largely kept the shape of the cup. Pressing down on it did not immediately cause it to collapse. Instead, the material appeared to push back against the pressure.
By studying these different shapes, the researchers could examine when granular materials flow, when they lock together and how they respond to compression or stretching.
The approach could dramatically reduce the number of calculations needed to create realistic digital sand. Instead of modeling every microscopic detail, computers could use carefully chosen grain shapes that reproduce important large-scale behaviors.
The researchers have so far concentrated mainly on predicting the final shape of a pile after the grains stop moving. Their next goal is to understand what happens while sand is still shifting, stopping and starting again—behavior that is especially important for simulating avalanches and rockslides.
The work remains basic research, but the team has made its code and data available to other scientists. Ultimately, their findings suggest that one simple question may hold the key to better simulations of enormously complicated piles of sand: What shape is each grain?
