ABSTRACT
Procedural snow deformation is one of the defining graphical features in the Rise of the Tomb Raider. At the core of this technology is a novel technique called deferred deformation, which decouples the deformation logic from the geometry it affects. This chapter aims to provide the reader with sufficient theoretical and practical knowledge to implement deferred deformation in a real-time 3D application. Deformation from dynamic objects is a key component in making snow look believable in 3D applications. The idea behind deferred deformation is as follows: during the snow render pass, the snow height is already provided by the vertices of the snow mesh. With deferred deformation, the cost shifts from rendering the deformation heightmap to reconstructing the depression and elevation during the snow render pass. This makes statically tessellated, high-poly snow meshes prohibitively expensive. Much of this cost is alleviated with adaptive tessellation and a reduced vertex count on the snow meshes.
