Geometric Queries on Tessellation-Free Displaced Surfaces

Abstract

Displacement maps encode fine geometric detail in compact textures and simplify surface authoring, but using them typically requires pre-tessellating surfaces into dense triangle meshes, incurring a heavy memory cost. Recent tessellation-free methods enable direct ray tracing. However, broader geometric queries such as surface sampling, specular manifold search, and closest-point queries remain less explored. Supporting these operations requires surface enclosures, area estimates, and normal bounds, which scalar height intervals alone do not fully provide. We present a first-order texture-space hierarchy that unlocks these queries directly without pre-tessellation. Each node stores a local affine height plane and a conservative residual bound, retaining spatial height variation that scalar minimum--maximum bounds discard. The plane and residual provide surface enclosures for intersection and distance searches, while the plane's height and slopes supply area estimates for sampling. Additional slope bounds support specular light-path search. Building on this representation, we develop query-specific traversal, pruning, and sampling algorithms, and demonstrate them in caustics rendering, sampling displaced emitters, and surface partial differential equation (PDE) solvers. We demonstrate memory savings over pre-tessellation and performance improvements over query-specific baselines, while retaining efficient ray tracing.