# Overview

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**HTrace SSGI** is a fully dynamic screen-space global illumination system that aims for accurate and responsive indirect lighting with detailed secondary shadows.

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## **Main Features**

* **Full Integration into the Rendering Pipeline \[HDRP]**: automatic resource injection with no need for manual setup or package customization. HTrace SSGI overrides native indirect lighting resources, ensuring compatibility with other rendering effects.
* **All Rendering Paths:** fully supports Deferred / Deferred+ / Forward / Forward+ rendering paths, with no visual or quality differences between them.&#x20;
* **All Light Sources:** compatible with all light types, including emissive materials that function as actual light sources and cast indirect soft shadows. Performance remains unaffected by the number of lights in the scene.
* **Dynamic Environments:** designed for fully dynamic and procedural environments where objects, materials, and lighting can change in real time with no extra performance cost or preprocessing.
* **APV Fallback & Enhancement:** natively supports Adaptive Probe Volumes as a fallback option. Enhances APV output by reducing light leaks and noise from low-resolution bakes, while adding fine GI details and occlusion from both static and dynamic objects.
* **Advanced Denoising:** powered by a cutting-edge ReSTIR Validation algorithm that maximizes temporal responsiveness, while preserving small details and keeping indirect shadows sharp during spatial filtering.
* **Scalability:** provides an adjustable Render Scale parameter for downscaled rendering, along with a wide range of options to fine-tune the effect and balance speed with quality.
* **Infinite light bounces:** simulated through a feedback loop, with each frame capturing an additional bounce of light.
* **Render Layer Mask:** selectively exclude objects from casting and/or receiving indirect lighting on a per-layer basis via the Render Layer Mask.
* **VR Support \[HDRP]**: single-pass VR is supported.
* **Open Code:** the code is open for modification. If you have questions about how it works, feel free to reach out to us on [Discord](https://discord.com/invite/zyjZkMe5Bv).

## Limitations and Requirements

* Unity **LTS** releases are recommended; bug fixes for **non-LTS** versions are not guaranteed.
* [**APV Fallback**](/htrace-ssgi/settings-and-properties/global-settings.md#fallback) in **URP** requires **Unity 6000.0** or newer.
* [**Exclude Casting**](/htrace-ssgi/settings-and-properties/global-settings.md#exclude-casting) / [**Receiving**](/htrace-ssgi/settings-and-properties/global-settings.md#exclude-receiving) options require **Unity 6000.0** or newer.
* **Orthographic Camera** is untested and not guaranteed to work correctly.
* **MSAA** is untested and not guaranteed to work correctly.

## Compatibility

* **Currently tested APIs are:** DX11 and DX12, Metal
* **Currently tested HDRP / URP versions are:** 14 and above.
* **Currently tested Unity versions are:** from 2022.2 to 6000.3.

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