# Spatial Denoising
## Filter Radius
Defines the radius of the anisotropic filtering disk. The higher the radius, the stronger the noise reduction — however, beyond a certain value, halo-like artifacts may appear around objects. It is recommended to use the lowest value that provides sufficient noise reduction.
*Performance impact: small*
{% tabs %}
{% tab title="Filter Radius 0.1" %}
{% endtab %}
{% tab title="Filter Radius 1" %}
{% endtab %}
{% endtabs %}
## Contact Occlusion
Adds an additional pass of screen-space occlusion with a very short radius. It runs at a later denoising stage (or even after denoising) and is meant to restore small details lost during spatial filtering, adding another layer of depth to the occlusion. The result of this pass is multiplied with the rest of the occlusion, creating further darkening in corners and at surface intersections. This parameter controls the overall intensity of contact occlusion. Setting it to 0 disables the effect entirely, saving performance.
*Performance impact: moderate*
{% tabs %}
{% tab title="Contact Occlusion 0" %}
{% endtab %}
{% tab title="Contact Occlusion 1" %}
{% endtab %}
{% endtabs %}
## Denoise \[Contact Occlusion]
Activates denoising of the Contact Occlusion effect. When enabled, Contact Occlusion is rendered before the second denoising pass and denoised together with the rest of the data during that pass. When disabled, Contact Occlusion is executed at the very end of the pipeline, providing maximum responsiveness at the cost of increased noise. This option is only shown when Resolution is set to **Full** and Denoising Mode is set to **Double Pass**.
{% hint style="warning" %}
If HTrace AO detects any form of temporal anti-aliasing or upscaling (e.g. TAA, STP, or DLSS) it automatically animates the Contact Occlusion noise pattern so it can be denoised by those temporal algorithms. This approach can be used as an alternative to enabling the **Denoise** option.
{% endhint %}
*Performance impact: none*
