> For the complete documentation index, see [llms.txt](https://ipgames.gitbook.io/htrace-ao/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ipgames.gitbook.io/htrace-ao/comparisons-with-unitys-ao/htrace-gtao-vs.-urp-ssao.md).

# HTrace GTAO vs. URP SSAO

{% hint style="warning" %}
The following comparison is performed in the HDRP Demo Scene on a laptop RTX 3060 6GB, 1920 x 1080 native.
{% endhint %}

## Overall Quality

URP's screen-space ambient occlusion appears to be based on the [The Alchemy Screen-Space Ambient Obscurance Algorithm](https://research.nvidia.com/sites/default/files/pubs/2011-08_The-Alchemy-Screen-space/paper.pdf) rather than any of the known horizon-based approaches. However, it's still closer to HTrace GTAO mode than to [SSAO mode](/htrace-ao/settings-and-properties/ssao-settings.md), so we will be comparing it against **HTrace GTAO**.

For the following 2 screenshots, both algorithms were tuned to roughly match in performance and visual appearance in terms of coverage and intensity. **URP SSAO** severely lacks small and medium scale detail, producing noticeable halo and stripe-like artifacts, and suffers from uneven occlusion.

{% tabs %}
{% tab title="URP SSAO (\~1.4ms)" %}

<figure><img src="/files/2liVAKh3GHUvKuk5iKmO" alt=""><figcaption></figcaption></figure>
{% endtab %}

{% tab title="HTrace GTAO (\~1.4ms)" %}

<figure><img src="/files/CDmGoctL3iA1DaPBRYVO" alt=""><figcaption></figcaption></figure>
{% endtab %}

{% tab title="URP SSAO Settings" %}

<figure><img src="/files/5B8CNIKUL1HVsDTYiOQr" alt="" width="465"><figcaption></figcaption></figure>
{% endtab %}

{% tab title="HTrace GTAO Settings" %}

<figure><img src="/files/xtKjUnZNTYwSfgsU9kzP" alt="" width="464"><figcaption></figcaption></figure>
{% endtab %}
{% endtabs %}

## Peak Quality

**URP SSAO** doesn't scale well in terms of tracing and denoising quality. As a result, even when performance or resolution are not limiting factors and higher quality is desired, it isn't always achievable with URP's occlusion. **HTrace GTAO** offers higher scalability, providing much better visual results.

{% hint style="warning" %}
**URP SSAO** parameters are set to the "High" preset here, while **HTrace GTAO** uses its medium to high settings.
{% endhint %}

{% tabs %}
{% tab title="URP SSAO" %}

<figure><img src="/files/QkxmSpa82iUKVR7Jw4Ga" alt=""><figcaption></figcaption></figure>
{% endtab %}

{% tab title="HTrace GTAO" %}

<figure><img src="/files/alA9YtcdHXWX03wZlj8d" alt=""><figcaption></figcaption></figure>
{% endtab %}
{% endtabs %}

## Resolution Scaling and Upscaling

Unlike **URP SSAO**, which offers only the [Downsample](https://docs.unity3d.com/6000.0/Documentation/Manual/urp/ssao-renderer-feature-reference.html) option, **HTrace GTAO** features 3 different [resolution modes](/htrace-ao/settings-and-properties/gtao-settings/gtao-quality.md#resolution): **Full**, **Half**, and **Quarter**, for more fine-grained performance control. On top of that, it provides a sharp and optimized upscaler for interpolating from any of these resolutions to the final target. This makes it more viable to render the effect at a lower resolution and then upscale it, retaining as much detail as possible.

{% tabs %}
{% tab title="URP SSAO Downsampled" %}

<figure><img src="/files/D7lyMQITF72ygzW4TiVJ" alt=""><figcaption></figcaption></figure>
{% endtab %}

{% tab title="HTrace GTAO Quarter Resolution" %}

<figure><img src="/files/kZM2NHIGDS2Up2GNEffO" alt=""><figcaption></figcaption></figure>
{% endtab %}
{% endtabs %}

## Additional Features <a href="#additional-features" id="additional-features"></a>

Here is the list of most notable features HTrace GTAO offers **that are not present** in URP's SSAO implementation:

* [Exclude Receiving](https://ipgames.gitbook.io/htrace-ao/v2/settings-and-properties/shared-settings/visuals#exclude-receiving)
* [Exclude Casting](/htrace-ao/settings-and-properties/gtao-settings/gtao-visuals.md#exclude-casting)
* [Max Screen Space Radius](/htrace-ao/settings-and-properties/gtao-settings/gtao-visuals.md#screen-space-radius)
* [Adaptive | Half | Quarter Resolution](/htrace-ao/settings-and-properties/gtao-settings/gtao-quality.md#resolution)
* [Visibility Bitmasks](/htrace-ao/settings-and-properties/gtao-settings/gtao-quality.md#tracing-mode)
* [Thickness Control](/htrace-ao/settings-and-properties/gtao-settings/gtao-quality.md#thickness-mode-visibility-bitmasks)
* [Separate Denoising Modes](/htrace-ao/settings-and-properties/gtao-settings/gtao-denoising.md#denoising-mode)
* [Output Dithering](/htrace-ao/settings-and-properties/gtao-settings/gtao-denoising.md#output-dithering-hdrp)
* [Temporal Denoising](/htrace-ao/settings-and-properties/gtao-settings/gtao-denoising/temporal-denoising.md)
* [Temporal Rejection](/htrace-ao/settings-and-properties/gtao-settings/gtao-denoising/temporal-denoising.md#rejection-threshold)
* [Sharp Temporal Reprojection](/htrace-ao/settings-and-properties/gtao-settings/gtao-denoising/temporal-denoising.md#reprojection-filter)
* [Spatial Filter Selection](/htrace-ao/settings-and-properties/gtao-settings/gtao-denoising/spatial-denoising.md#filter-type)