Make responsive snow scenes

Sean Puller explains how to make a dynamic and believeable snow deformation in Unreal Engine 4

Make dynamic snow environments, creating foot imprints and snow angels in Unreal Engine 4

r ealism is important when it comes to the effects in video games. Uncanny valley doesn’t just apply to character models, it applies to effects as well. If a character running across the snow doesn’t leave footprints, or if they throw another character to the ground and an imprint isn’t left, the player will get an Uncanny Valley response. This reminds them that what they are looking at isn’t real and it prevents them from becoming fully immersed in both the game’s story and its world.

After reading a GDC presentation about the deformable snow rendering used in Batman: Arkham Origins, I really liked this ‘outside the box’ solution and wanted to recreate the effect in Unreal Engine. Once the Draw Material to Render Target node was introduced in version 4.13, I knew I had all I needed to create the effect.

The effect is basically a camera looking directly up from under the ground, which can only see as high as the deformation of the snow mesh. When something enters the view of the camera, a heightmap is generated. This is used to deform the vertices for the snow mesh downwards – back to their original state. This creates the appearance that the object is deforming the snow.

It’s easy to see how this snow deformation will perform much better than simulating millions of particles but will give similar results. By using visible geometry as opposed to collision geometry to deform the snow, you don’t need additional work on the creation of assets for them to interact with the snow.