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Hand-authoring LPE can be a tedious process and for artists it's not always desired to do these manually. This document aims to improve the artist's understanding and usage of LPE. Understanding these concepts and applying them will make you a hero to many pipelines given the power and flexibility of the feature. |
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In production it often becomes necessary to create non-physical effects and art-directed changes to your shot. Light Path Expressions (LPE) are a powerful way to collect and output specific light paths for alteration later.
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An excellent primer with useful visuals can be found in a tutorial video from Lollipop Shaders. Begin at Class 6 for the LPE introduction. |
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Diffuse Reflection: lpe:C<RD>*[<L.>O] Specular Reflection: lpe:C<RS>*[<L.>O] |
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Diffuse Transmission: lpe:C<TD>*[<L.>O] Specular Transmission: lpe:C<TS>*[<L.>O] |
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A specular scene using iridescence and transmission (glass).
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Now that we have some understanding of the main components, let's begin by looking at the parts used to organize an LPE
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The curly brackets can also take a range of values to render a set of bounces. Maybe you're only interested in collecting the effects of the 4th through 8th bounce? Or maybe you know where to begin or end but want the renderer to decide where that is.
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The Beauty Render
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