| On this page |
Previous Noise
Overview ¶
Looking at the beauty pass is usually enough to tell where more path traced samples are needed.
While the beauty pass alpha channel is helpful, adding 
Cryptomatte AOVs can be even more useful to identify under-sampled primitive edges in complex scenes. If any of the following features are grainy or noisy (in the beauty, alpha, or Cryptomatte planes), start increasing the primary samples until the quality is where you want it:
-
Noisy hair or fur (BasisCurves), or aliased edges of geometry.
-
Strands of curves look pixelated or noisy.
-
Noisy motion blur, or aliased depth of field.
The primarysamples AOV can be useful to inspect, if increasing primary samples doesn’t seem to improve quality. This can happen for renders dominated by depth of field (DOF) or motion blur quality. If the actual number of pixel samples aren’t reaching the value set in the Primary Samples parameter, the pixel oracle is probably preventing sufficient pixel sampling. Try lowering the oracle’s Variance Threshold and see if that sends more pixel samples. If it doesn’t, you can continue to increase primary samples, or switch over to the uniform pixel oracle.
In path traced convergence mode (the only mode available in Karma XPU), adding more path traced samples is main control you have for reducing all types of noise.
Decrease the Variance Threshold of the pixel oracle can reduce noise. Inspecting the primarysamples AOV can tell you if the oracle is limiting the pixel samples, or if you need to increase the path traced samples. This can be done with the Inspect tool in the Viewport, Mplay, and Render Gallery. You may need to increase Path Traced Samples if a lower variance threshold isn’t improving your image.
You can increase Light Sampling Quality for better shadows, but otherwise reducing noise requires adding more path traced samples.
Path Traced Properties
Tip
Setting path traced samples to values that are easily squared (i.e. 4, 9, 16, 25, etc…) may help to resolve noise in some cases.
Tips ¶
-
Shaders or scenes with lots of bounces or SSS can cause the Optix devices to do a lot more work. This may result in their contributing to a smaller percentage of the render overall.
-
Shader compile times can cause a delay in the initial frame rendering. Because of this, rendering multiple frames in the same process can improve rendering iterations with Karma XPU a lot.