Stateless Level of Detail Lighting for Automotive Visualization

Abstract

Car models typically consist of highly specular surfaces including sharp angles. Renderings of such models contain very fine, sharp lighting features, that both make Level-of-Detail switches well visible and result in strong aliasing artifacts. In this paper we address both issues. As Level-of-Detail approach, we apply on-the-fly vertex clustering and introduce a texture coordinate correction to remove popping artifacts, that become visible during mesh simplification. By replacing vertex normals with texture normals, we can provide stable lighting features, even if the underlying mesh changes. To prevent aliasing effects on specular highlights, we then apply a variant of LEAN mapping (linear efficient antialiased normal mapping). We observe that LEAN mapping cannot be applied directly, because in our scenario we need to filter object space normals, as we have no presupposed tangent-space availeble. We therefore create a per-texel tangent space from an object space MIP normal, thus retaining the benefits of a 2D distribution without a preexisting tangent space. Both approaches in combination, allow us to render highly reflective, detailed models with continuous level of detail and anti-aliased lighting, at the price of moderately increased memory consumption and render time.