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title: "Introduction to Light Path Expressions"
canonical: "https://documentation.chaos.com/space/VRAYHOUDINI/113279503/Introduction%20to%20Light%20Path%20Expressions"
format: markdown
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## **Overview**

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If you are not familiar with using Light Path Expressions (LPEs), this page is a good place to start. The sections below will try to explain what LPEs are, how they work and what are the possible use cases.

> ✅ The[ Light Path Expressions article](https://docs-chaos.atlassian.net/wiki/spaces/VRAYHOUDINI/pages/113279441) goes into greater detail about complex LPE usage and concepts.


## **What are LPEs?**

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Light Path Expressions are a special type of render element with advanced capabilities. They use regular expression patterns to record selected events of light contribution along the path of a ray.

This can be used for very fine control in compositing by allowing you to tweak, for example, the GI coming from lights, the environment or self-illuminating objects separately, or each separate GI bounce, or the self-reflections of an object or the way SSS is seen behind refraction without re-rendering. The possible applications are practically endless.


## **Light Paths**

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## **Ray Spawn Events and Scattering Types**

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