Abstract
We present the first method to efficiently predict antialiasing footprints to pre-filter color-, normal-, and displacement-mapped appearance in the context of multi-bounce global illumination. We derive Fourier spectra for radiance and importance functions that allow us to compute spatial-angular filtering footprints at path vertices for both uni- and bi-directional path construction. We then use these footprints to antialias reflectance modulated by high-resolution maps (such as color and normal maps) encountered along a path. In doing so, we also unify the traditional path-space formulation of light transport with our frequency-space interpretation of global illumination pre-filtering. Our method is fully compatible with all existing single bounce pre-filtering appearance models, not restricted by path length, and easy to implement atop existing path-space renderers. We illustrate its effectiveness on several radiometrically complex scenarios where previous approaches either completely fail or require orders of magnitude more time to arrive at similarly high-quality results.
Highlights
Texturing with color, normal and displacement maps is a common approach to modelling fine details, increasing a scene’s apparent complexity
Local prefiltering of color textures [Heckbert 1986] and, most recently, normal and displacement maps [Han et al 2007; Dupuy et al 2013; Yan et al 2014], is a well understood problem; all existing prefilters works only treat directly visible surface appearance, projecting the pixel footprint onto the geometry
Very little work has investigated the implications of high-resolution appearance aliasing in the presence of complex light transport with global illumination (GI)
Summary
Normal and displacement maps is a common approach to modelling fine details, increasing a scene’s apparent complexity. Whenever such textures are used, accurate and efficient antialiasing approaches are necessary to avoid objectionable aliasing artifacts. Prefiltering appearance in the presence of GI poses several challenges: since final pixel color results from a multi-dimensional integration of light paths incident on the pixel’s footprint (and reflected towards a viewer), we need to express and propagate the pixel footprint across multiple bounces (e.g., at each light path vertex; see Figure 5). Filtering should be applied at each vertex along a light path, where the final appearance is correctly antialiased by band-limiting its content by the frequency content of the sensor/pixel, emitters/lights, and reflectance along the path
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