Efficient Caustic Rendering with Lightweight Photon Mapping

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epilectrolytics
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Efficient Caustic Rendering with Lightweight Photon Mapping

Post by epilectrolytics » Wed May 13, 2020 3:39 pm

Maybe this can help to make light tracing more efficient?

Abstract
Robust and efficient rendering of complex lighting effects, such as caustics, remains a challenging task. While algorithms like vertex connection and merging can render such effects robustly, their significant overhead over a simple path tracer is not always justified and – as we show in this paper ‐ also not necessary. In current rendering solutions, caustics often require the user to enable a specialized algorithm, usually a photon mapper, and hand‐tune its parameters. But even with carefully chosen parameters, photon mapping may still trace many photons that the path tracer could sample well enough, or, even worse, that are not visible at all. Our goal is robust, yet lightweight, caustics rendering. To that end, we propose a technique to identify and focus computation on the photon paths that offer significant variance reduction over samples from a path tracer. We apply this technique in a rendering solution combining path tracing and photon mapping. The photon emission is automatically guided towards regions where the photons are useful, i.e., provide substantial variance reduction for the currently rendered image. Our method achieves better photon densities with fewer light paths (and thus photons) than emission guiding approaches based on visual importance. In addition, we automatically determine an appropriate number of photons for a given scene, and the algorithm gracefully degenerates to pure path tracing for scenes that do not benefit from photon mapping.

Efficient Caustic Rendering with Lightweight Photon Mapping

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FarbigeWelt
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Re: Efficient Caustic Rendering with Lightweight Photon Mapping

Post by FarbigeWelt » Fri May 15, 2020 1:11 pm

Efficient Caustic Rendering with Grittmann, Pascal & Pérard-Gayot, Arsène & Slusallek, Philipp & Krivanek, Jaroslav. (2018). Efficient Caustic Rendering with Lightweight Photon Mapping. Computer Graphics Forum. 37. 133-142. 10.1111/cgf.13481.

Thank you for this link.
Regarding caustics only I think Dade introduced a more efficient way in LuxCoreRender. One part in the paper sounds interesting: Their algorithm optimizes indirect light from caustics too.
I found the following illustration in this paper a nice idea for an own little render series.
illustration - author's 'ours'-method:  Lightweight Photon Mapping
illustration - author's 'ours'-method: Lightweight Photon Mapping
Lightweight Photon Mapping]
glass-Cube,-yellow-Ring,-wandering-Sun - click to view animation - thx
glass-Cube,-yellow-Ring,-wandering-Sun - click to view animation - thx
:D
Light and Word designing Creator - www.farbigewelt.ch - aka quantenkristall || #luxcorerender
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lacilaci
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Re: Efficient Caustic Rendering with Lightweight Photon Mapping

Post by lacilaci » Fri May 15, 2020 1:26 pm

This doesn't seem to be capable of rendering sds caustics(like current caustic cache can in luxcore)
So I'd say it's more like simple caustics, or basic or partial.. I don't know, if the caustics can't be indirectly visible it's not a proper caustics solution

epilectrolytics
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Re: Efficient Caustic Rendering with Lightweight Photon Mapping

Post by epilectrolytics » Fri May 15, 2020 1:54 pm

paper wrote:The photon emission is automatically guided towards regions where the photons are useful, i.e., provide substantial variance reduction for the currently rendered image. Our method achieves better photon densities with fewer light paths
I posted this because we have repeatedly encountered issues where metropolis was not able to "guide the photons where they are useful" (too big bounding box, flicker).
Not understanding the math I have no idea if this could help LuxCore with its advanced light tracing + SDS-cache tech, but just in case . . . ;)

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