From ray optics to wave optics.
In this paper we present the generalized ray: an extension of the classical ray to wave optics.
The generalized ray retains the defining characteristics of the ray-optical ray: locality and linearity.
These properties allow the generalized ray to serve as a ``point query'' of light's behaviour---the same purpose that the classical ray fulfils in rendering.
By using such generalized rays, we enable the rendering of complex scenes, like the one shown, under rigorous wave-optical light transport.
Materials admitting diffractive optical phenomena are visible: (a) a Bornite ore with a layer of copper oxide causing interference; (b) a Brazilian Rainbow Boa, whose scales are biological diffraction grated surfaces; and (c) a Chrysomelidae beetle, whose colour arises due to naturally-occurring multilayered interference reflectors in its elytron.
Our formalism serves as a link between path tracing techniques and wave optics, and admits a highly general validity domain.
Therefore, we are able to apply sophisticated sampling techniques, and achieve performance that surpasses the state-of-the-art by orders-of-magnitude.
We indicate resolution and samples-per-pixel (spp) count in all figures rendered using our method.
While these figures showcase converged (high spp) results, our implementation also allows interactive rendering of all these scenes at 1 spp.
Frame times (at 1 spp) for interactive rendering are indicated.
Implementation, as well as additional renderings and videos are available in our supplemental material.
Abstract
Under ray-optical light transport, the classical ray serves as a local and linear “point query” of light’s behaviour. Such point queries are useful, and sophisticated path tracing and sampling techniques enable efficiently computing solutions to light transport problems in complex, real-world settings and environments. However, such formulations are firmly confined to the realm of ray optics, while many applications of interest, in computer graphics and computational optics, demand a more precise understanding of light. We rigorously formulate the generalized ray, which enables local and linear point queries of the wave-optical phase space. Furthermore, we present sample-solve: a simple method that serves as a novel link between path tracing and computational optics. We will show that this link enables the application of modern path tracing techniques for wave-optical rendering, improving upon the state-of-the-art in terms of the generality and accuracy of the formalism, ease of application, as well as performance. Sampling using generalized rays enables interactive rendering under rigorous wave optics, with orders-of-magnitude faster performance compared to existing techniques.
This is the pre peer-reviewed archival version of the article.
Revisions
April 12, 2023
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Added double-slit interference experiment (Figure 6) and discussion about interference aliasing (Section 4.3), and related changes.
This discussion serves to illustrate the important process of interference aliasing, which highlights (i) why the traditional mental depiction of interference (phasors observed at singular points) is misleading; and, (ii) how generalized ray always remain mutually incoherent, even in the presence of fully-coherent light.
