Reducing Noise

The following guidelines can help you reduce noise in your renders:

GI Clamp - Reduce Kernel > GI Clamp. This clamps the energy of rays, reducing fireflies and other noise. OTOY recommend values of 10-100x the inverse of the exposure. Try values from 1 to 10.
Adaptive SamplingA method of sampling that determines if areas of a rendering require more sampling than other areas instead of sampling the entire rendering equally. - Enable Kernel > Adaptive Sampling. Adaptive sampling renders noisy areas with more samples.
Caustic Blur - Increase Kernel > Caustic Blur. This smoothes out caustic and reflection noise. Try 0.3.
Denoising - Enable Camera > Imager > Enable Denoising. This uses AI to intelligently denoise the render. You may also enable Denoise Volumes if there are volumes in your scene.
Hotpixel Removal - Reduce Camera > Imager > Hotpixel Removal. This removes fireflies using a post-process. Try 0.5. Lower values may blur the rendered image too much.
Emitter Geometry - When using emitter geometry, use low polygon surfaces, like a single polygon plane.
Path Term. Power - If you have noise in dark areas, this may be due to paths being terminated early, so try reducing Kernel > Path Term. Power.
Lighting and Exposure - If you need to set your Camera > Imager > Exposure substantially higher than 1.0, then there is not enough light in your scene. Increase the power of your emitters and/or HDR environment, then reduce your exposure to compensate.
Portals - If your scene lighting needs to get into an enclosed space through windows, place Portals at the window openings.
Fake Shadows - Try enabling Fake Shadows on your glass (SpecularAmount of specular reflection, or the mirror-like reflection of light photons at the same angle. Used for transparent materials such as glass and water.) materials.
Emitters Behind Glass - Avoid placing emitters behind glass if possible. Try using an additional emitter over the glass instead, and hide its visibility using opacity (or light visibility options).
PMC Kernel - If a majority of your scene lighting needs to pass through glass materials, an alternative is to try using the PMC Kernel instead of Path Tracing. You may also reduce Kernel > Direct Light Importance, to give greater priority to the light passing through the glass.

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