Microfacet Billboarding
Abstract
Rendering of intricately shaped objects that are soft or cluttered is
difficult because we cannot accurately acquire their complete
geometry. Since their geometry varies drastically, modeling them
using fixed facets can lead to severe artifacts when viewed from
singular directions. In this paper, we propose a novel modeling
method, ``microfacet billboarding,'' which uses view-dependent
``microfacets'' with view-dependent textures. The facets discretely
approximate the geometry of the object and are aligned perpendicular
to the viewing direction. The texture of each facet is selected from
the most suitable texture images according to the
viewpoint. Microfacet billboarding can render intricate geometry from
various viewpoints. We first describe the basic algorithm of
microfacet billboarding. Also, we predict artifacts generated due to
the use of discrete facets and we analyze the necessary sampling
interval of the geometry and texture for regarding the artifacts as
negligible. In addition to the modeling method, we have implemented a
real-time renderer by a hardware-accelerated technique. To evaluate
the efficiency of our method, we compared it with traditional texture
mapping to a mesh model, and showed that our method has a great
advantage over the former in rendering intricately shaped objects.